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Default Electric motor on KBC mill

At an internet auction a few days ago I bought a KBC bench mill. The
model is Grip-16.

The pictures neglected to show a view of the mill that is clearly
stamped "3 phase". I thought the motor was single phase because the
auction listed it as "230v". Until today, apparently in error, I
thought that 3 phase motors were 208V.

However, the KBC tools web site for this mill almost leads me to
believe that the motor can be wired for single or 3 phase.

Will somebody help me out here? A motor is either single or 3 phase
but can't be changed. Yes?

I already understand that a 3 phase machine can be operated from
single phase with a phase converter. And I may have to go in that
direction unless I can get a single phase replacement motor.

This mill was built in 1989. Since even when new it wasn't a high end
precision machine would it be prudent to check the accuracy of the X Y
table? As we get deeper into machining I'm sure I will join the quest
for split hair precision. But for now, we just wanna play.

On Monday I will call KBC and look into my options. But meanwhile,
any advice on how to logically approach the aftermath of a possibly
illogical purchase will be appreciated.

Regards and thanks,

Vernon
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Default Electric motor on KBC mill

Hey Vernon,

Comments on Rotary Phase Converter (RPC).
Is there anything "better"? Yes.
Anything cheaper? Probably no. Anything easier? Probably yes, but
not a whole lot.
Anything that even a less than fully equipped shop can not do? No, it
can be REALLY simple.
Smallest foot-print? No, by far the biggest, but it can be at some
distance, and easily "tucked out of the way".
Anything sophisticated? Not necessarily.
Easy to find parts locally? Probably, but depends on where you are
located and considering "locally" to be within an hours drive.

Probably a bunch more questions too, but my "first" RPC was just
another 3Phase motor the same size as the one I wanted to drive, and
coupled directly to a 1/2 HP 1750RPM 120volt single phase from a
furnace fan that I had laying around. The direct coupling in my case
meant V-belt and pulleys. There are certainly a few more
sophisticated options, but this method does away with all the
"electronics". The smaller motor is first turned on and allowed to
get the larger 3phase up to speed, and then the 220 is applied to the
RPC generator motor, and voila...3 phase is available. Kinda crappy
3phase, but good enough to drive your mill. To me, one, if not the
only, non-replaceable feature of 3phase is the instant reversibility
of the mill or lathe spindle.

I note (after I started to type this) that another poster replied with
a webpage for an RPC circuit. That's the "sophisticated" stuff, and
has to do with self-starting, versus my suggestion of "manual
starting". Nothing wrong with that at all if you have the
skill/talent and time and inclination. It IS what I have now of
course, but I first wanted to see mine run!

Take care.

Brian Lawson,
Bothwell, Ontario.
XXXXXXXXXXXXXXX

On Fri, 26 Sep 2008 21:22:43 -0700 (PDT), Vernon
wrote:

At an internet auction a few days ago I bought a KBC bench mill. The
model is Grip-16.

The pictures neglected to show a view of the mill that is clearly
stamped "3 phase". I thought the motor was single phase because the
auction listed it as "230v". Until today, apparently in error, I
thought that 3 phase motors were 208V.

However, the KBC tools web site for this mill almost leads me to
believe that the motor can be wired for single or 3 phase.

Will somebody help me out here? A motor is either single or 3 phase
but can't be changed. Yes?

I already understand that a 3 phase machine can be operated from
single phase with a phase converter. And I may have to go in that
direction unless I can get a single phase replacement motor.

This mill was built in 1989. Since even when new it wasn't a high end
precision machine would it be prudent to check the accuracy of the X Y
table? As we get deeper into machining I'm sure I will join the quest
for split hair precision. But for now, we just wanna play.

On Monday I will call KBC and look into my options. But meanwhile,
any advice on how to logically approach the aftermath of a possibly
illogical purchase will be appreciated.

Regards and thanks,

Vernon

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Default Electric motor on KBC mill

On Sep 27, 7:56*am, Brian Lawson wrote:
Hey Vernon,

Comments on Rotary Phase Converter (RPC). *
Is there anything "better"? *Yes. *
Anything cheaper? Probably no. *Anything easier? *Probably yes, but
not a whole lot. *
Anything that even a less than fully equipped shop can not do? *No, it
can be REALLY simple. *
Smallest foot-print? *No, by far the biggest, but it can be at some
distance, and easily "tucked out of the way".
Anything sophisticated? *Not necessarily.
Easy to find parts locally? *Probably, but depends on where you are
located and considering "locally" to be within an hours drive.

Probably a bunch more questions too, but my "first" RPC was just
another 3Phase motor the same size as the one I wanted to drive, and
coupled directly to a 1/2 HP 1750RPM 120volt single phase from a
furnace fan that I had laying around. *The direct coupling in my case
meant V-belt and pulleys. *There are certainly a few more
sophisticated options, but this method does away with all the
"electronics". *The smaller motor is first turned on and allowed to
get the larger 3phase *up to speed, and then the 220 is applied to the
RPC generator motor, and voila...3 phase is available. *Kinda crappy
3phase, but good enough to drive your mill. *To me, one, if not the
only, non-replaceable feature of 3phase is the instant reversibility
of the mill or lathe spindle.

I note (after I started to type this) that another poster replied with
a webpage for an RPC circuit. *That's the "sophisticated" stuff, and
has to do with self-starting, versus my suggestion of "manual
starting". *Nothing wrong with that at all if you have the
skill/talent and time and inclination. *It IS what I have now of
course, but I first wanted to see mine run!

Take care.

Brian Lawson,
Bothwell, Ontario.
XXXXXXXXXXXXXXX

On Fri, 26 Sep 2008 21:22:43 -0700 (PDT), Vernon
wrote:



At an internet auction a few days ago I bought a KBC bench mill. *The
model is Grip-16.


The pictures neglected to show a view of the mill that is clearly
stamped "3 phase". * I thought the motor was single phase because the
auction listed it as "230v". *Until today, apparently in error, I
thought that 3 phase motors were 208V.


However, the KBC tools web site for this mill almost leads me to
believe that the motor can be wired for single or 3 phase.


Will somebody help me out here? *A motor is either single or 3 phase
but can't be changed. *Yes?


I already understand that a 3 phase machine can be operated from
single phase with a phase converter. *And I may have to go in that
direction unless I can get a single phase replacement motor.


This mill was built in 1989. *Since even when new it wasn't a high end
precision machine would it be prudent to check the accuracy of the X Y
table? *As we get deeper into machining I'm sure I will join the quest
for split hair precision. *But for now, we just wanna play.


On Monday I will call KBC and look into my options. *But meanwhile,
any advice on how to logically approach the aftermath of a possibly
illogical purchase will be appreciated.


Regards and thanks,


Vernon- Hide quoted text -


- Show quoted text -


To everybody who answered. Thanks! Upon reflection a rotary phase
converter will suit us to a tee. I have already started googling and
quickly found some "how to" instructions. About a year ago, when I
went to pick up an auction item I bought, the auctioneer gave me a
huge plenum box that sat atop a multi-story commercial building. It
was the cooler / blower for the entire building! It is a large, well
insulated box, containing a large blower driven by a 3 phase motor. I
don't know the horse power of the motor. But I'm guessing about 15
HP.

I also don't know the voltage. But I will find out tomorrow when we
go to our farm. For purposes of discussion and assuming that it IS a
15 HP, 240V 3 phase motor, would this be overkill as an idler motor?
I actually have a couple of other 3 phase tools I've had forever that
I haven't been able to use for the same reason. One of these is a
very large band saw!

It sounds like with a properly designed and built unit I can power all
of this stuff simultaneously. These a a 48" bandsaw, a Delta
Unisaw, and the newly acquired mill. The band saw probably has the
biggest motor. But I'm pretty sure all of these motors are smaller
than the motor in the air conditioner blower box.

Tomorrow I will get the technical specs off the motor data plate.

Thanks to all.

Vernon

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Default Electric motor on KBC mill

Vernon,

Kudos on your enthusiasm for the machine arts. While you're gathering information on phase
converters check into Metalweb News. FWIW, a 15 HP 3-phase motor would make an excellent rotary
phase converter. The only consideration might be the amount of power consumption while running
idle. That is typically about 1/6 or so of full-load rated HP. Suggest you consult an electrician
for wire and breaker sizes.

Bob Swinney
"Vernon" wrote in message
...
At an internet auction a few days ago I bought a KBC bench mill. The
model is Grip-16.

The pictures neglected to show a view of the mill that is clearly
stamped "3 phase". I thought the motor was single phase because the
auction listed it as "230v". Until today, apparently in error, I
thought that 3 phase motors were 208V.

However, the KBC tools web site for this mill almost leads me to
believe that the motor can be wired for single or 3 phase.

Will somebody help me out here? A motor is either single or 3 phase
but can't be changed. Yes?

I already understand that a 3 phase machine can be operated from
single phase with a phase converter. And I may have to go in that
direction unless I can get a single phase replacement motor.

This mill was built in 1989. Since even when new it wasn't a high end
precision machine would it be prudent to check the accuracy of the X Y
table? As we get deeper into machining I'm sure I will join the quest
for split hair precision. But for now, we just wanna play.

On Monday I will call KBC and look into my options. But meanwhile,
any advice on how to logically approach the aftermath of a possibly
illogical purchase will be appreciated.

Regards and thanks,

Vernon

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Default Electric motor on KBC mill

On Sat, 27 Sep 2008 19:23:28 -0700 (PDT), Vernon
wrote:


To everybody who answered. Thanks! Upon reflection a rotary phase
converter will suit us to a tee. I have already started googling and
quickly found some "how to" instructions. About a year ago, when I
went to pick up an auction item I bought, the auctioneer gave me a
huge plenum box that sat atop a multi-story commercial building. It
was the cooler / blower for the entire building! It is a large, well
insulated box, containing a large blower driven by a 3 phase motor. I
don't know the horse power of the motor. But I'm guessing about 15
HP.

I also don't know the voltage. But I will find out tomorrow when we
go to our farm. For purposes of discussion and assuming that it IS a
15 HP, 240V 3 phase motor, would this be overkill as an idler motor?
I actually have a couple of other 3 phase tools I've had forever that
I haven't been able to use for the same reason. One of these is a
very large band saw!

It sounds like with a properly designed and built unit I can power all
of this stuff simultaneously. These a a 48" bandsaw, a Delta
Unisaw, and the newly acquired mill. The band saw probably has the
biggest motor. But I'm pretty sure all of these motors are smaller
than the motor in the air conditioner blower box.

Tomorrow I will get the technical specs off the motor data plate.


Depending on the building size it could be anywhere from 10HP to
50HP - and anything over 15 would most likely be 480V or 240/480V.
Unless you are talking Canada, then it could be 575V.

Be careful to provide cooling if needed - some of those motors are
rated "Air Over" on the nameplate, and have to have external forced
air cooling flow. The motor mounted inside the fan plenum would have
cooled itself, but not if you reuse it as a rotary converter - you
will need a fan.

Even if you get a small propeller style fan for a condensing unit
and put it on the output shaft - they make "Universal" blades and hubs
that mix and match, because you will have a Big Shaft and only need a
little blade.

-- Bruce --



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Default Electric motor on KBC mill

On Sep 27, 12:38*am, Joseph Gwinn wrote:
In article
,





*Vernon wrote:
At an internet auction a few days ago I bought a KBC bench mill. *The
model is Grip-16.


The pictures neglected to show a view of the mill that is clearly
stamped "3 phase". * I thought the motor was single phase because the
auction listed it as "230v". *Until today, apparently in error, I
thought that 3 phase motors were 208V.


However, the KBC tools web site for this mill almost leads me to
believe that the motor can be wired for single or 3 phase.


Will somebody help me out here? *A motor is either single or 3 phase
but can't be changed. *Yes?


I already understand that a 3 phase machine can be operated from
single phase with a phase converter. *And I may have to go in that
direction unless I can get a single phase replacement motor.


This mill was built in 1989. *Since even when new it wasn't a high end
precision machine would it be prudent to check the accuracy of the X Y
table? *As we get deeper into machining I'm sure I will join the quest
for split hair precision. *But for now, we just wanna play.


On Monday I will call KBC and look into my options. *But meanwhile,
any advice on how to logically approach the aftermath of a possibly
illogical purchase will be appreciated.


Buy a VFD to run the mill. *Three phase works very well. *Many VFDs can
be driven from 220 volt single phase, with a derating.

Joe Gwinn- Hide quoted text -

- Show quoted text -


Joseph,

I'm still trying to wrap my electrically challenged brain around the
differences / advantages / disadvantages between rotary converters and
VFDs. As soon as I'm able to articulate an intelligent question I'll
ask one!

V
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Default Electric motor on KBC mill

Vernon writes:


Joseph,


I'm still trying to wrap my electrically challenged brain around the
differences / advantages / disadvantages between rotary converters and
VFDs. As soon as I'm able to articulate an intelligent question I'll
ask one!


A VFD is a big magic solid state box that delivers AC of from {say} 10Hz
to 100Hz. It USUALLY will be one able to deliver 3 phase power. [But
there may well be smaller single phase ones, so cabbage emperor...]

How it does that.... Well think of it as an audio oscillator and a
BIG amplifier for the speakers err motor.

Its major plus is the variable frequency means whatever motor it feeds
will be variable speed. It's almost a waste to buy one just for a single
speed task, but a friend did to drive an air compressor.


A rotary converter is a semi-kludgey way of getting 3 phase from a single
speed source, at the line freq. [60 Hz]. Ditto the capacitor-based
schemes. They may work well enough for your case. But neither one will
deliver the large starting torque a true 3ph supply will offer.

Does this help?
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
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Default Electric motor on KBC mill

On Sep 29, 12:47*am, David Lesher wrote:
Vernon writes:
Joseph,
I'm still trying to wrap my electrically challenged brain around the
differences / advantages / disadvantages between rotary converters and
VFDs. *As soon as I'm able to articulate an intelligent question I'll
ask one!


A VFD is a big magic solid state box that delivers AC of from {say} 10Hz
to 100Hz. It USUALLY will be one able to deliver 3 phase power. [But
there may well be smaller single phase ones, so cabbage emperor...]

How it does that.... Well think of it as an audio oscillator and a
BIG amplifier for the speakers err motor.

Its major plus is the variable frequency means whatever motor it feeds
will be variable speed. It's almost a waste to buy one just for a single
speed task, but a friend did to drive an air compressor.

A rotary converter is a semi-kludgey way of getting 3 phase from a single
speed source, at the line freq. [60 Hz]. Ditto the capacitor-based
schemes. *They may work well enough for your case. But neither one will
deliver the large starting torque a true 3ph supply will offer.

Does this help?
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433


Hi David,

It does help. But I don't understand this part:

"They may work well enough for your case. But neither one will
deliver the large starting torque a true 3ph supply will offer."

Are you saying that a VFD is "a true 3ph supply..."? Or are you saying
that "nothing's as good as having 3 phase and not NEEDING a box"?

V
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Default Electric motor on KBC mill

Vernon writes:


It does help. But I don't understand this part:


"They may work well enough for your case. But neither one will
deliver the large starting torque a true 3ph supply will offer."


Are you saying that a VFD is "a true 3ph supply..."? Or are you saying
that "nothing's as good as having 3 phase and not NEEDING a box"?


A 3ph VFD will deliver real, balanced, 3-phase. The other two hacks do not;
you may or may not be able to live with their limitations.

Utility 3phase has one major plus -- a LOT of starting capacity courtesy
of the grid. Well, two -- the cost! But the minus is -- single speed.

I've not taken one apart, but I assume a VFD is really a switcher supply
[thread tie-in!] within. In short, it takes single phase 240VAC, makes
DC, has an oscillator and inverter and makes AC with it.

That's basically how the VFD built into a rail transit car such as Metro
here works; except it starts with 700 volt DC from the third rail. You
can hear some of the cars sing as they start up; I think the upgraded
300 series are the most obvious. Before we had VFD's, we needed DC motors
to have speed control; I think all the DC-motor cars here are upgraded by
now.



--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
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Default Electric motor on KBC mill

Vernon wrote:
... I need to do this on the
cheap for the moment. Would one of those "motor ready" boxes on the
market be cost effective? ...


Here's cheap: a starting cap & a push button. Wire the cap & PB in
series between either line leg & the generated leg. To operate: push
the button, turn on the power, when the motor is up to speed release the
button. That's how I use an RPC on my mill & it works fine. It is not
balanced, but balance is not something I need, nor do you, in all
likelihood.

HTH,
Bob
--
Nota for President


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Default Electric motor on KBC mill

Vernon wrote:
...
While I like the idea of the VFD converters I need to do this on the
cheap for the moment. Would one of those "motor ready" boxes on the
market be cost effective? It looks like the box wouldn't be more than
about $200 - $250. Even if I could build it cheaper the convenience
would be worth a lot to me right now.


You can get a VFD for less than 200 - 250.

Bob
---
Nota for President
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Default Electric motor on KBC mill

On Sep 29, 3:03*pm, Bob Engelhardt wrote:
Vernon wrote:
*...
While I like the idea of the VFD converters I need to do this on the
cheap for the moment. *Would one of those "motor ready" boxes on the
market be cost effective? *It looks like the box wouldn't be more than
about $200 - $250. *Even if I could build it cheaper the convenience
would be worth a lot to me right now.


You can get a VFD for less than 200 - 250.

Bob
---
Nota for President


Hey Bob,

While from a technology standpoint it looks like a VFD is the way to
go I'm concerned about their operational requirements. For example
one site states its units require less than 90% humidity for storage
and operation. We are on the humid Texas Gulf Coast. Humidity is
extremely high although I don't remember what percentage the
weatherman normally quotes.

I'm looking at one that is 10HP. If I go down this road I might as
well buy one big enough to operate some other 3 phase tools I bought
long ago and never put to any use.

Vernon
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Default Electric motor on KBC mill

Vernon writes:


While from a technology standpoint it looks like a VFD is the way to
go I'm concerned about their operational requirements. For example
one site states its units require less than 90% humidity for storage
and operation. We are on the humid Texas Gulf Coast. Humidity is
extremely high although I don't remember what percentage the
weatherman normally quotes.


So park a 60 watt lamp under it....


I'm looking at one that is 10HP. If I go down this road I might as
well buy one big enough to operate some other 3 phase tools I bought
long ago and never put to any use.


THAT is true!
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
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Default Electric motor on KBC mill

On 2008-09-29, Vernon wrote:

[ ... ]

Don and everybody.

The motor in the plenum blower is a Baldor "Super E". If I correctly
read the data plate with my head stuck into an awkward backward
position the specs a 7.5 HP, 3ph, 1750rpm. It draws 20 amps at
230v and 10 amps at 460v.


O.K. 20A from a real three phase line -- but about 24A from
single phase.

And this is in the range of what can sometimes be found at
semi-reasonable prices. I have a 30A VFD which can and does run from a
30A single phase 240V line to power thing rather smaller than 7.5 HP.

I got it (by luck) at a hamfest some ten years ago or so for
$115.00 IIRC. Quite reasonable, anyway.

But I've acquired more (more reasonably sized) VFDs to have a
separate one on each machine, because you really don't want to have
switches between the VFD and the motor -- though that big 30A one is
surviving a switch between it and the 1HP motor on my Nichols horizontal
mill.

Actually, I'm somewhat relieved that it's not 15HP. As one of you
mentioned, I was concerned about the power consumption of a 15HP idler
motor.


And the current necessary to spin it up at the start.

Plus, that's bigger than anything I am likely to need to power
in the near future.


And bigger than you could really run from your breaker box
perhaps?

While I like the idea of the VFD converters I need to do this on the
cheap for the moment. Would one of those "motor ready" boxes on the
market be cost effective? It looks like the box wouldn't be more than
about $200 - $250. Even if I could build it cheaper the convenience
would be worth a lot to me right now.


If it is designed for a motor of your 7.5 HP range, why not.
You may still want to add capacitors for tuning and for equalizing the
power factor to keep the current through your circuit breaker panel down
to reasonable levels and avoid nuisance trips.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
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On 2008-09-29, Vernon wrote:
On Sep 27, 12:38*am, Joseph Gwinn wrote:


[ ... ]

Buy a VFD to run the mill. *Three phase works very well. *Many VFDs can
be driven from 220 volt single phase, with a derating.


[ ... ]

I'm still trying to wrap my electrically challenged brain around the
differences / advantages / disadvantages between rotary converters and
VFDs. As soon as I'm able to articulate an intelligent question I'll
ask one!


Quick and dirty:

VFD
Pros: Gives you the ability to vary speed while running over a wide
range.

Very efficient compared to a rotary converter.

Can be set up to accelerate the motor over a programmable time,
so you don't draw as heavy a current from the wall to get the
motor up to speed.

Quiet.

Cons: Does not like having switching between the motor and the VFD,
this generates high voltage spikes during the switching, and can
blow the output transistors.

So -- rewire the switch on the machine to command
start/stop/reverse to the VFD's control terminals and you are
fine for driving a *single* machine at a time. Best to have a
separate VFD per machine -- among other things so you can adjust
the speed of one without affecting the others.

ROTARY Converter
Pros: Fairly simple to make.

Can be tuned to minimize current draw and maximize three phase
quality.

Can easily run multiple machines (if large enough) because it
does not care whether you have switches between it and the load
motors. The other machines running actually add to the capacity
of the RPC so you can handle a larger motor on the next machine
turned on.

If the idler motor in the RPC is enough larger than the motor in
the machine, it can handle "plug" reversing (switching to
reverse while at full speed forward). If the idler motor is not
large enough (say the same HP as the machine's motor), attempts
to plug reverse sometimes result in the RPC reversing instead of
the machine. This can get exciting if your machine is about to
hit something (more likely on a lathe than a mill).

Cons: Wastes power idling when there is no load turned on, so you
probably want to remember to turn it off.

Some of that waste power is turned to noise which can be
annoying (but which will remind you to shut it off when you are
done -- if you don't banish it to a box outside the house to
keep the shop quieter. :-)

Draws a heavy current spike when first starting before you ever
turn on your machine.

Depending on the nature of your particular motor, you may need
to provide additional fan cooling.

There are probably other things which I have not thought of, but
others may add to the list.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
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On Sep 29, 7:27*pm, "DoN. Nichols" wrote:
On 2008-09-29, Vernon wrote:

On Sep 27, 12:38*am, Joseph Gwinn wrote:


* * * * [ ... ]

Buy a VFD to run the mill. *Three phase works very well. *Many VFDs can
be driven from 220 volt single phase, with a derating.


* * * * [ ... ]

I'm still trying to wrap my electrically challenged brain around the
differences / advantages / disadvantages between rotary converters and
VFDs. *As soon as I'm able to articulate an intelligent question I'll
ask one!


* * * * Quick and dirty:

VFD
Pros: * Gives you the ability to vary speed while running over a wide
* * * * range.

* * * * Very efficient compared to a rotary converter.

* * * * Can be set up to accelerate the motor over a programmable time,
* * * * so you don't draw as heavy a current from the wall to get the
* * * * motor up to speed.

* * * * Quiet.

Cons: * Does not like having switching between the motor and the VFD,
* * * * this generates high voltage spikes during the switching, and can
* * * * blow the output transistors.

* * * * So -- rewire the switch on the machine to command
* * * * start/stop/reverse to the VFD's control terminals and you are
* * * * fine for driving a *single* machine at a time. *Best to have a
* * * * separate VFD per machine -- among other things so you can adjust
* * * * the speed of one without affecting the others.

ROTARY Converter
Pros: * Fairly simple to make.

* * * * Can be tuned to minimize current draw and maximize three phase
* * * * quality.

* * * * Can easily run multiple machines (if large enough) because it
* * * * does not care whether you have switches between it and the load
* * * * motors. *The other machines running actually add to the capacity
* * * * of the RPC so you can handle a larger motor on the next machine
* * * * turned on.

* * * * If the idler motor in the RPC is enough larger than the motor in
* * * * the machine, it can handle "plug" reversing (switching to
* * * * reverse while at full speed forward). *If the idler motor is not
* * * * large enough (say the same HP as the machine's motor), attempts
* * * * to plug reverse sometimes result in the RPC reversing instead of
* * * * the machine. This can get exciting if your machine is about to
* * * * hit something (more likely on a lathe than a mill).

Cons: * Wastes power idling when there is no load turned on, so you
* * * * probably want to remember to turn it off.

* * * * Some of that waste power is turned to noise which can be
* * * * annoying (but which will remind you to shut it off when you are
* * * * done -- if you don't banish it to a box outside the house to
* * * * keep the shop quieter. :-)

* * * * Draws a heavy current spike when first starting before you ever
* * * * turn on your machine.

* * * * Depending on the nature of your particular motor, you may need
* * * * to provide additional fan cooling.

* * * * There are probably other things which I have not thought of, but
others may add to the list.

* * * * Enjoy,
* * * * * * * * DoN.

--
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Holy Smokes. You guys are awesome!

Vernon
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On 2008-09-29, David Lesher wrote:
Vernon writes:


Joseph,


I'm still trying to wrap my electrically challenged brain around the
differences / advantages / disadvantages between rotary converters and
VFDs. As soon as I'm able to articulate an intelligent question I'll
ask one!


A VFD is a big magic solid state box that delivers AC of from {say} 10Hz
to 100Hz. It USUALLY will be one able to deliver 3 phase power. [But
there may well be smaller single phase ones, so cabbage emperor...]


There are smaller ones designed to *run* only from single phase,
and power a 1/8 HP motor (I have one -- about the volume of a brick and
a lot lighter).

But not for driving normal single phase motors at variable
speeds. The tricks which start single phase motors are rather frequency
sensitive. Most capacitor start ones will need a different value of
capacitor for each frequency range -- rather impractical.

Shaded-pole induction motors (such as old phonograph motors or
little fan motors (pre muffin fan style) use a trick consisting of a
heavy shorted winding around only part of each pole, causing a phase
shift at that end of the pole to nudge the motor to a start. This is
rather frequency sensitive as well. I've played with such a motor and a
VFD -- and you get some range of variable speed, but for below say 60%
speed, or above perhaps 120% speed, the motor will simply stall. So it
is not practical.

How it does that.... Well think of it as an audio oscillator and a
BIG amplifier for the speakers err motor.


Except that it is normally done by PWM (Pulse Width Modulation)
so the transistors driving it can simply switch fully on or off (both low
power conditions), and avoid the half-on state where the maximum power
is dissipated in the transistor -- generating heat and leading to
failure.

Its major plus is the variable frequency means whatever motor it feeds
will be variable speed.


Whatever *three* *phase* motor will be. Single phase will not
be happy. :-)

It's almost a waste to buy one just for a single
speed task, but a friend did to drive an air compressor.


Air compressors can draw a *lot* of power, and running one from
a VFD (if you run it a lot) will probably cover the cost of the VFD in
power bill savings over two or three years. They are close to 100%
efficient because of the switching mode output, while a RPC is rather
inefficient.

A rotary converter is a semi-kludgey way of getting 3 phase from a single
speed source, at the line freq. [60 Hz]. Ditto the capacitor-based
schemes. They may work well enough for your case. But neither one will
deliver the large starting torque a true 3ph supply will offer.


Actually -- a *larger* idler motor than the load motor (1.5x or
2x) will probably provide all the torque you need -- especially if you
take time to balance the converter by adding capacitors between the
generated phase and the other two legs to produce approximately equal
current in each leg.

The capacitor start only certainly throws away motor horsepower,
at least for full-time operation. Someone here has measured produced
horsepower from the cap start trick and found that the motor will
produce that full horsepower -- but the current through the only powered
winding is much higher than that when it is driven from true three
phase, so long term operation can wind up burning out the motor's
windings.

Enjoy,
DoN.

--
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On Mon, 29 Sep 2008 14:53:27 -0700 (PDT), Vernon
wrote:

On Sep 29, 3:03*pm, Bob Engelhardt wrote:
Vernon wrote:
*...
While I like the idea of the VFD converters I need to do this on the
cheap for the moment. *Would one of those "motor ready" boxes on the
market be cost effective? *It looks like the box wouldn't be more than
about $200 - $250. *Even if I could build it cheaper the convenience
would be worth a lot to me right now.


You can get a VFD for less than 200 - 250.

Bob
---
Nota for President


Hey Bob,

While from a technology standpoint it looks like a VFD is the way to
go I'm concerned about their operational requirements. For example
one site states its units require less than 90% humidity for storage
and operation. We are on the humid Texas Gulf Coast. Humidity is
extremely high although I don't remember what percentage the
weatherman normally quotes.

I'm looking at one that is 10HP. If I go down this road I might as
well buy one big enough to operate some other 3 phase tools I bought
long ago and never put to any use.

Vernon



VFDs are to be used on a SINGLE machine. Now you can use them to run a
bunch of machines, but only ONE AT A TIME!!!!


"Obama, raises taxes and kills babies. Sarah Palin - raises babies
and kills taxes." Pyotr Flipivich
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Default Electric motor on KBC mill

On Sep 29, 7:42*pm, "DoN. Nichols" wrote:
On 2008-09-29, David Lesher wrote:

Vernon writes:


Joseph,


I'm still trying to wrap my electrically challenged brain around the
differences / advantages / disadvantages between rotary converters and
VFDs. *As soon as I'm able to articulate an intelligent question I'll
ask one!


A VFD is a big magic solid state box that delivers AC of from {say} 10Hz
to 100Hz. It USUALLY will be one able to deliver 3 phase power. [But
there may well be smaller single phase ones, so cabbage emperor...]


* * * * There are smaller ones designed to *run* only from single phase,
and power a 1/8 HP motor (I have one -- about the volume of a brick and
a lot lighter).

* * * * But not for driving normal single phase motors at variable
speeds. *The tricks which start single phase motors are rather frequency
sensitive. *Most capacitor start ones will need a different value of
capacitor for each frequency range -- rather impractical.

* * * * Shaded-pole induction motors (such as old phonograph motors or
little fan motors (pre muffin fan style) use a trick consisting of a
heavy shorted winding around only part of each pole, causing a phase
shift at that end of the pole to nudge the motor to a start. *This is
rather frequency sensitive as well. *I've played with such a motor and a
VFD -- and you get some range of variable speed, but for below say 60%
speed, or above perhaps 120% speed, the motor will simply stall. *So it
is not practical.

How it does that.... Well think of it as an audio oscillator and a
BIG amplifier for the speakers err motor.


* * * * Except that it is normally done by PWM (Pulse Width Modulation)
so the transistors driving it can simply switch fully on or off (both low
power conditions), and avoid the half-on state where the maximum power
is dissipated in the transistor -- generating heat and leading to
failure.

Its major plus is the variable frequency means whatever motor it feeds
will be variable speed.


* * * * Whatever *three* *phase* motor will be. *Single phase will not
be happy. :-)

* * * * * * * * * * * * It's almost a waste to buy one just for a single
speed task, but a friend did to drive an air compressor.


* * * * Air compressors can draw a *lot* of power, and running one from
a VFD (if you run it a lot) will probably cover the cost of the VFD in
power bill savings over two or three years. *They are close to 100%
efficient because of the switching mode output, while a RPC is rather
inefficient.

A rotary converter is a semi-kludgey way of getting 3 phase from a single
speed source, at the line freq. [60 Hz]. Ditto the capacitor-based
schemes. *They may work well enough for your case. But neither one will
deliver the large starting torque a true 3ph supply will offer.


* * * * Actually -- a *larger* idler motor than the load motor (1..5x or
2x) will probably provide all the torque you need -- especially if you
take time to balance the converter by adding capacitors between the
generated phase and the other two legs to produce approximately equal
current in each leg.

* * * * The capacitor start only certainly throws away motor horsepower,
at least for full-time operation. *Someone here has measured produced
horsepower from the cap start trick and found that the motor will
produce that full horsepower -- but the current through the only powered
winding is much higher than that when it is driven from true three
phase, so long term operation can wind up burning out the motor's
windings.

* * * * Enjoy,
* * * * * * * * DoN.

--
*Email: * * | Voice (all times): (703) 938-4564
* * * * (too) near Washington D.C. |http://www.d-and-d.com/dnichols/DoN.html
* * * * * *--- Black Holes are where God is dividing by zero ---


In the case of this mill it has an instant reverse switch on the left
side. Today KBC priced a single phase replacement motor at over $500
dollars plus almost a hundred for the replacement instant reverse
switch. Grizzly has some single phase motors that might work for
less than half of KBC's price.

It's beginning to sound like the advantages are tilting to a VFD.
That seems to be the most direct path to instant gratification.

By the way, I probably don't understand what an "instant reverse" is
or why its needed. But if I understood one of the explanations of the
pros and cons of VFDs if I buy a VFD I will need to remove the instant
reverse switch and start / stop switch wires from the motor circuit
and route them to the input side of the VFD.

Provided I do this correctly and get a VFD of adequate capacity I will
have nearly perfect 3 phase, full horse power, and full use of the
instant reverse switch.

Did I understand correctly? If so, I may pull out my credit card
tomorrow while it still works!

V
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"Vernon" wrote in message
...
On Sep 29, 7:42 pm, "DoN. Nichols" wrote:
On 2008-09-29, David Lesher wrote:

Vernon writes:


Joseph,


I'm still trying to wrap my electrically challenged brain around the
differences / advantages / disadvantages between rotary converters and
VFDs. As soon as I'm able to articulate an intelligent question I'll
ask one!


A VFD is a big magic solid state box that delivers AC of from {say} 10Hz
to 100Hz. It USUALLY will be one able to deliver 3 phase power. [But
there may well be smaller single phase ones, so cabbage emperor...]


There are smaller ones designed to *run* only from single phase,
and power a 1/8 HP motor (I have one -- about the volume of a brick and
a lot lighter).

But not for driving normal single phase motors at variable
speeds. The tricks which start single phase motors are rather frequency
sensitive. Most capacitor start ones will need a different value of
capacitor for each frequency range -- rather impractical.

Shaded-pole induction motors (such as old phonograph motors or
little fan motors (pre muffin fan style) use a trick consisting of a
heavy shorted winding around only part of each pole, causing a phase
shift at that end of the pole to nudge the motor to a start. This is
rather frequency sensitive as well. I've played with such a motor and a
VFD -- and you get some range of variable speed, but for below say 60%
speed, or above perhaps 120% speed, the motor will simply stall. So it
is not practical.

How it does that.... Well think of it as an audio oscillator and a
BIG amplifier for the speakers err motor.


Except that it is normally done by PWM (Pulse Width Modulation)
so the transistors driving it can simply switch fully on or off (both low
power conditions), and avoid the half-on state where the maximum power
is dissipated in the transistor -- generating heat and leading to
failure.

Its major plus is the variable frequency means whatever motor it feeds
will be variable speed.


Whatever *three* *phase* motor will be. Single phase will not
be happy. :-)

It's almost a waste to buy one just for a single
speed task, but a friend did to drive an air compressor.


Air compressors can draw a *lot* of power, and running one from
a VFD (if you run it a lot) will probably cover the cost of the VFD in
power bill savings over two or three years. They are close to 100%
efficient because of the switching mode output, while a RPC is rather
inefficient.

A rotary converter is a semi-kludgey way of getting 3 phase from a
single
speed source, at the line freq. [60 Hz]. Ditto the capacitor-based
schemes. They may work well enough for your case. But neither one will
deliver the large starting torque a true 3ph supply will offer.


Actually -- a *larger* idler motor than the load motor (1.5x or
2x) will probably provide all the torque you need -- especially if you
take time to balance the converter by adding capacitors between the
generated phase and the other two legs to produce approximately equal
current in each leg.

The capacitor start only certainly throws away motor horsepower,
at least for full-time operation. Someone here has measured produced
horsepower from the cap start trick and found that the motor will
produce that full horsepower -- but the current through the only powered
winding is much higher than that when it is driven from true three
phase, so long term operation can wind up burning out the motor's
windings.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. |http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---


In the case of this mill it has an instant reverse switch on the left
side. Today KBC priced a single phase replacement motor at over $500
dollars plus almost a hundred for the replacement instant reverse
switch. Grizzly has some single phase motors that might work for
less than half of KBC's price.

It's beginning to sound like the advantages are tilting to a VFD.
That seems to be the most direct path to instant gratification.

By the way, I probably don't understand what an "instant reverse" is
or why its needed. But if I understood one of the explanations of the
pros and cons of VFDs if I buy a VFD I will need to remove the instant
reverse switch and start / stop switch wires from the motor circuit
and route them to the input side of the VFD.

Provided I do this correctly and get a VFD of adequate capacity I will
have nearly perfect 3 phase, full horse power, and full use of the
instant reverse switch.

Did I understand correctly? If so, I may pull out my credit card
tomorrow while it still works!

V


To get the near instant reversing, you will probably need to add a correctly
sized braking resistor to the drive to bleed off excess energy regenerated
into the drive when the motor is being stopped or reversed quickly.

John




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Default Electric motor on KBC mill

On Sep 29, 8:20*pm, Gunner Asch wrote:
On Mon, 29 Sep 2008 14:53:27 -0700 (PDT), Vernon
wrote:





On Sep 29, 3:03*pm, Bob Engelhardt wrote:
Vernon wrote:
*...
While I like the idea of the VFD converters I need to do this on the
cheap for the moment. *Would one of those "motor ready" boxes on the
market be cost effective? *It looks like the box wouldn't be more than
about $200 - $250. *Even if I could build it cheaper the convenience
would be worth a lot to me right now.


You can get a VFD for less than 200 - 250.


Bob
---
Nota for President


Hey Bob,


While from a technology standpoint it looks like a VFD is the way to
go I'm concerned about their operational requirements. *For example
one site states its units require less than 90% humidity for storage
and operation. *We are on the humid Texas Gulf Coast. *Humidity is
extremely high although I don't remember what percentage the
weatherman normally quotes.


I'm looking at one that is 10HP. *If I go down this road I might as
well buy one big enough to operate some other 3 phase tools I bought
long ago and never put to any use.


Vernon


VFDs are to be used on a SINGLE machine. Now you can use them to run a
bunch of machines, but only ONE AT A TIME!!!!

"Obama, raises taxes and kills babies. *Sarah Palin - raises babies
and kills taxes." Pyotr Flipivich- Hide quoted text -

- Show quoted text -


Hey Gunner, I used to talk with you on the welding site. V
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"DoN. Nichols" writes:

A VFD is a big magic solid state box that delivers AC of from {say} 10Hz
to 100Hz. It USUALLY will be one able to deliver 3 phase power. [But
there may well be smaller single phase ones, so cabbage emperor...]


There are smaller ones designed to *run* only from single phase,
and power a 1/8 HP motor (I have one -- about the volume of a brick and
a lot lighter).


But not for driving normal single phase motors at variable
speeds.



Don, I was specifically trying to keep it simple and on-topic. The OP's
concern is getting a VFD {or other solution} for his case. I just didn't
want him buying some weird eBay VFD that WAS single phase...because
he assumed "VFD == 3 phase"

How it does that.... Well think of it as an audio oscillator and a
BIG amplifier for the speakers err motor.


Except that it is normally done by PWM (Pulse Width Modulation)


Again....TMI

It's almost a waste to buy one just for a single speed task, but a
friend did to drive an air compressor.


Air compressors can draw a *lot* of power, and running one from a VFD
(if you run it a lot) will probably cover the cost of the VFD in power
bill savings over two or three years. They are close to 100% efficient
because of the switching mode output, while a RPC is rather inefficient.


This runs a big hammer -- I suspect it's occasional use only. He had
3 phase very nearby, but the utility wanted lot$ to bring it in.


A rotary converter is a semi-kludgey way of getting 3 phase from a single

.....

Actually -- a *larger* idler motor than the load motor (1.5x or
2x) will probably provide all the torque you need -- especially if you
take time to balance the converter by adding capacitors between the
generated phase and the other two legs to produce approximately equal
current in each leg.


And how many ram types would do that?

I will admit I'd not considered the instant reverse aspect. That might be
reason for the rotary converter approach.
--
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is busy, hung or dead....................................20915-1433
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Default Electric motor on KBC mill

On 2008-09-30, Vernon wrote:

[ ... ]

In the case of this mill it has an instant reverse switch on the left
side. Today KBC priced a single phase replacement motor at over $500
dollars plus almost a hundred for the replacement instant reverse
switch. Grizzly has some single phase motors that might work for
less than half of KBC's price.


Ouch!

It's beginning to sound like the advantages are tilting to a VFD.
That seems to be the most direct path to instant gratification.


Yes.

By the way, I probably don't understand what an "instant reverse" is
or why its needed.


Well ... picture using the mill to drive a large tap through
steel or some other metal.

Now -- assume that it is thick enough so you need to bury almost
the whole length of the tap in the workpiece.

And -- that you are using a rigid tap holder (most commonly used
in a CNC (Computer Numeric Control) controlled mill which can feed
downward at precisely the right speed linked to the spindle speed), or a
"floating" tap holder (which allows the spindle to feed a little faster
or slower than the thread wants to feed), but you do not have a
"relasing" tap holder, which will stop driving the tap when it is pulled
a certain short distance down from the spindle. Since as long as the
spindle rotates, the tap will keep feeding in -- or break when you run
out of threaded part of the tap.

So -- you want to be able to hit a button which will start the
tap rotating the other way, so it backs out of the hole -- *before* you
break the tap.

The "instant" will be a little slower than the instant from
commercial three phase power (the "plug" reversing which I mentioned in
another article in this thread), but it can be tuned to be fast enough
so your reflex time will be the true limiting factor. (And it can be
tuned a lot faster on a mill spindle than on a lathe spindle with a big
heavy chuck and big heavy workpiece adding to the rotational inertia.

Of course -- you could use something like a Tapmatic tapping
head, which will stop turning the tap when the tap gets a certain
distance ahead of the feed, and when you reverse the feed, the tap
starts turning backwards faster than it went in -- all while the mill's
spindle is rotating the same direction. I use a couple of these of
different sizes on my drill press.

But if I understood one of the explanations of the
pros and cons of VFDs if I buy a VFD I will need to remove the instant
reverse switch and start / stop switch wires from the motor circuit
and route them to the input side of the VFD.


That is right.

Provided I do this correctly and get a VFD of adequate capacity I will
have nearly perfect 3 phase, full horse power, and full use of the
instant reverse switch.


Yes -- except just very slightly slower in the reverse -- but
also will minimize the high current spikes which you would otherwise put
into your power panel.

Did I understand correctly? If so, I may pull out my credit card
tomorrow while it still works!


Take the time to pick one which is more affordable. Others here
can suggest a couple of sources which give good prices and good service.
IIRC, one is called "Dealer's Electric", and they have a web page.

Enjoy,
DoN.

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Vernon sez:
"Provided I do this correctly and get a VFD of adequate capacity I will
have nearly perfect 3 phase, full horse power, and full use of the
instant reverse switch."

Yeah! And if you get a RPC it will do all these things as well as allow you to run more than a
single 3-phase machine at a time.

Bob (RPC) Swinney




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On 2008-09-30, David Lesher wrote:
"DoN. Nichols" writes:

A VFD is a big magic solid state box that delivers AC of from {say} 10Hz
to 100Hz. It USUALLY will be one able to deliver 3 phase power. [But
there may well be smaller single phase ones, so cabbage emperor...]


There are smaller ones designed to *run* only from single phase,
and power a 1/8 HP motor (I have one -- about the volume of a brick and
a lot lighter).


But not for driving normal single phase motors at variable
speeds.



Don, I was specifically trying to keep it simple and on-topic. The OP's
concern is getting a VFD {or other solution} for his case. I just didn't
want him buying some weird eBay VFD that WAS single phase...because
he assumed "VFD == 3 phase"


Have you *ever* seen a VFD -- on eBay or elsewhere -- which was
single phase output? I haven't, and I think that it because there is
not much benefit from variable frequency with single phase motors.

How it does that.... Well think of it as an audio oscillator and a
BIG amplifier for the speakers err motor.


Except that it is normally done by PWM (Pulse Width Modulation)


Again....TMI


Perhaps -- but I find people here like to know the "why" of an
answer, not just the "you can (or can't) do it" type of response.

[ ... ]

Air compressors can draw a *lot* of power, and running one from a VFD
(if you run it a lot) will probably cover the cost of the VFD in power
bill savings over two or three years. They are close to 100% efficient
because of the switching mode output, while a RPC is rather inefficient.


This runs a big hammer -- I suspect it's occasional use only. He had
3 phase very nearby, but the utility wanted lot$ to bring it in.


O.K. So to him, the benefit is not having a noisy rotary
converter generating heat between operations. He can leave the VFD on
full time if he wants, and get very little waste power.


A rotary converter is a semi-kludgey way of getting 3 phase from a single

....

Actually -- a *larger* idler motor than the load motor (1.5x or
2x) will probably provide all the torque you need -- especially if you
take time to balance the converter by adding capacitors between the
generated phase and the other two legs to produce approximately equal
current in each leg.


And how many ram types would do that?


You mean rcm? Quite a few have -- and I first learned about it
from the studies that Fitch (used to be a regular here) posted in a
series of articles as he studied the construction of a rotary converter
for his shop.

The balancing gives you lots quicker starting (more torque), and
the final capacitors across the input line to the rotary converter
corrects the power factor, so a 10A load won't draw 30A through the
breaker, causing lots of nuisance trips. It also keeps the wiring
cooler. Note that it does *not* save much money (just a little for the
extra heat generated in the wiring), because *residential* power meters
measure true Watts, not Volt-Amps which can be very different with an
uncorrected rotary converter.

I will admit I'd not considered the instant reverse aspect. That might be
reason for the rotary converter approach.


It is one reason. The ability to connect multiple machines to a
single converter, and not have to play tricks with the
forward/stop/reverse switching to pass the commands to the VFD (instead
of risking zapping the output transistors by putting a switch between
the VFD's output and the motor, as most machine tools are wired, since
they expect the three phase to be coming from the power company.

And *I* can't get commercial three phase (even though it runs
past about a quarter block from here (you've seen my place -- just up at
the top of the hill there is medium HV three phase passing by)) -- in
part because of town regulations -- which prohibit any hobby machine
tool with a 3HP or larger motor. Even if I could, the charge from the
power company is well beyond what I can afford -- and they charge
industrial rates for three phase -- which means that they base the
charge on the peak current draw during the month, and you pay as though
you have drawn that much full time through the month.

Enjoy,
DoN.

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Default Electric motor on KBC mill

"DoN. Nichols" writes:

Don, I was specifically trying to keep it simple and on-topic. The OP's
concern is getting a VFD {or other solution} for his case. I just didn't
want him buying some weird eBay VFD that WAS single phase...because
he assumed "VFD == 3 phase"


Have you *ever* seen a VFD -- on eBay or elsewhere -- which was
single phase output? I haven't, and I think that it because there is
not much benefit from variable frequency with single phase motors.


Nope; but if it existed, someone likely got suckered on eBay....

Again....TMI


Perhaps -- but I find people here like to know the "why" of an
answer, not just the "you can (or can't) do it" type of response.


No dispute, but to me it looked we were swamping the OP with data...


O.K. So to him, the benefit is not having a noisy rotary
converter generating heat between operations. He can leave the VFD on
full time if he wants, and get very little waste power.


Don't know; but he can speak for himself if he wishes...

And how many ram types would do that?


You mean rcm? Quite a few have -- and I first learned about it
from the studies that Fitch (used to be a regular here) posted in a
series of articles as he studied the construction of a rotary converter
for his shop.


OK, I'll take your judgement on same...


And *I* can't get commercial three phase (even though it runs
past about a quarter block from here (you've seen my place -- just up at
the top of the hill there is medium HV three phase passing by)) -- in
part because of town regulations -- which prohibit any hobby machine
tool with a 3HP or larger motor.


Sure you can. It may involve paying off someone ["Motor? Naw, he has a
3 phase electric furnace to heat his basement. Nothing larger than a
clock motor at his house...."] at City Hall or....

Even if I could, the charge from the power company is well beyond what I
can afford -- and they charge industrial rates for three phase -- which
means that they base the charge on the peak current draw during the
month, and you pay as though you have drawn that much full time through
the month.


The other person found that was the case there, too. The 3-phase order
form came with an enema kit disguised as the rate schedule...

Of course, as a big single-phase user; I bet he now makes all his
neighbors lights blink, so the utility will spend $$$ to upgrade that....

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
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Default Electric motor on KBC mill

On Sep 30, 6:47*pm, David Lesher wrote:
"DoN. Nichols" writes:
Don, I was specifically trying to keep it simple and on-topic. The OP's
concern is getting a VFD {or other solution} for his case. I just didn't
want him buying some weird eBay VFD that WAS single phase...because
he assumed "VFD == 3 phase"

* *Have you *ever* seen a VFD -- on eBay or elsewhere -- which was
single phase output? *I haven't, and I think that it because there is
not much benefit from variable frequency with single phase motors.


Nope; but if it existed, someone likely got suckered on eBay....

Again....TMI

* *Perhaps -- but I find people here like to know the "why" of an
answer, not just the "you can (or can't) do it" type *of response.


No dispute, but to me it looked we were swamping the OP with data...

* *O.K. *So to him, the benefit is not having a noisy rotary
converter generating heat between operations. *He can leave the VFD on
full time if he wants, and get very little waste power.


Don't know; but he can speak for himself if he wishes...

And how many ram types would do that?

* *You mean rcm? *Quite a few have -- and I first learned about it
from the studies that Fitch (used to be a regular here) posted in a
series of articles as he studied the construction of a rotary converter
for his shop.


OK, I'll take your judgement on same...

* *And *I* can't get commercial three phase (even though it runs
past about a quarter block from here (you've seen my place -- just up at
the top of the hill there is medium HV three phase passing by)) -- in
part because of town regulations -- which prohibit any hobby machine
tool with a 3HP or larger motor. *


Sure you can. It may involve paying off someone ["Motor? Naw, he has a
3 phase electric furnace to heat his basement. Nothing larger than a
clock motor at his house...."] at City Hall or....

Even if I could, the charge from the power company is well beyond what I
can afford -- and they charge industrial rates for three phase -- which
means that they base the charge on the peak current draw during the
month, and you pay as though you have drawn that much full time through
the month.


The other person found that was the case there, too. The 3-phase order
form came with an enema kit disguised as the rate schedule...

Of course, as a big single-phase user; I bet he now makes all his
neighbors lights blink, so the utility will spend $$$ to upgrade that....

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433


Gentlemen,

Swamp away. I may not understand it. But I want it. All of it. I am
a very studious fellow. Sort of like a python swallowing a large
meal. It may take a while but I'll get there...

Here's the critter I bought:

http://www.driveswarehouse.com/Drive...0-022NFU2.html

I think I've figured out that both types of converter are in my
future. The VFD shipped today. It should get the bench mill running.

Today I began taking inventory of some of the other 3 phase stuff I've
bought over the years. What happened was this. There was a time I
thought that getting 3 phase service to me was imminent. Then the
electric company threw me a curve ball. That's why I happen to have
this stuff.

Among the items gathering dust is a Delta Unisaw (table saw). It has
a 7.5 HP motor. The freebie plenum box has a 7.5 HP motor.

Although I'm told it's good to have an idler motor that's a little
bigger than the load I hope to be able to roll my own rotary phase
converter from the motor in the plenum box. I will make the most
rudimentary thing possible. Once I've determined that both motors run
I will attempt to finesse the thing into something more
sophisticated. It should help to have the mill up and running so that
I can make stuff for the project. Of course I make that statement
pretending I have a clue about lathes and mills. But I don't.

Nevertheless, I do have a modest library of books on the subject.
I've been mining ebay for years for old books that pre-date the
computer age. At least several of these are encyclopedic manuals on
machining.

Here's a more basic question for your collective wisdom. Where to
mount the mill? I have a very heavy duty table that came as a base
for a Diacro single station hole punch. The foot print of the table
is just a tad wider than the mill base. But the base is just a tad
longer (1") than the table.

Notwithstanding that the table is strong enough I'm worried about the
high center of gravity. If I bolt the table to the floor and the mill
to the table does that sound like a suitable arrangement?

Or should the mill be on a big heavy, long table?

Then there's tooling. I hope to buy some kind of lot assortment on
ebay. I looked tonight. A couple of guys are selling it saying
they're retiring. Of course I still don't know an end mill from a
collet.

Tomorrow morning we're off to Wichita Falls to fetch the lathe.

Thanks to all.

Vernon
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Default Electric motor on KBC mill

On 2008-10-01, Vernon wrote:
On Sep 30, 6:47*pm, David Lesher wrote:
"DoN. Nichols" writes:


[ ... discussion over whether this was too much information
snipped ... ]

Gentlemen,

Swamp away. I may not understand it. But I want it. All of it. I am
a very studious fellow. Sort of like a python swallowing a large
meal. It may take a while but I'll get there...


Good approach.

Here's the critter I bought:

http://www.driveswarehouse.com/Drive...0-022NFU2.html


That one looks nice. One thing which you should consider,
however, is where the metal chips will fly from your tools. Set it up
so they won't get into those louvers in the sides, because it can get
exciting if they reach the circuitry. :-)

Simplest thing would be a wood frame around it with window
screening all around it, and some easy way to get inside if you need to
use the front panel controls. This should keep the chips out, and let
air flow through to cool it.

If you're going to add a braking resistor (if you decide that
you *need* instant reverse), you want it to mount to metal, not wood, to
avoid fire. In use those can get fairly hot.

I think I've figured out that both types of converter are in my
future. The VFD shipped today. It should get the bench mill running.


O.K.

Today I began taking inventory of some of the other 3 phase stuff I've
bought over the years. What happened was this. There was a time I
thought that getting 3 phase service to me was imminent. Then the
electric company threw me a curve ball. That's why I happen to have
this stuff.


I understand.

Among the items gathering dust is a Delta Unisaw (table saw). It has
a 7.5 HP motor. The freebie plenum box has a 7.5 HP motor.


O.K. A bit marginal, and you may have to take the time to tune
it to make it start the saw reliably. And you want the saw located as
far from the mill (and other machine tools) as possible. Sawdust from
some woods is acidic and can cause rust where you don't want it.

Although I'm told it's good to have an idler motor that's a little
bigger than the load I hope to be able to roll my own rotary phase
converter from the motor in the plenum box.


Yes. If you turn out to need a little more capability to start
the saw, hang another three phase motor on the RPC, start it after the
RPC is started, and it will help to start the saw.

I will make the most
rudimentary thing possible.


That may or may not be sufficient for starting the saw. Try it,
and if you have problems, add tuning and then an extra idler motor.

Once I've determined that both motors run
I will attempt to finesse the thing into something more
sophisticated.


O.K. You can probably test the idler motor (perhaps with the
fan removed) by driving it from the VFD.

It should help to have the mill up and running so that
I can make stuff for the project. Of course I make that statement
pretending I have a clue about lathes and mills. But I don't.


Hey -- I find that having a project in mind while learning a
tool (or a computer program) makes it easier to learn more and faster,
because you have something to hang what you read on. Later, re-read wit
another project in mind, and you will pick up other things.

Nevertheless, I do have a modest library of books on the subject.
I've been mining ebay for years for old books that pre-date the
computer age. At least several of these are encyclopedic manuals on
machining.


Great!

Here's a more basic question for your collective wisdom. Where to
mount the mill? I have a very heavy duty table that came as a base
for a Diacro single station hole punch. The foot print of the table
is just a tad wider than the mill base. But the base is just a tad
longer (1") than the table.


Hmm ... bolt some steel or thick aluminum plate to the table,
and then bolt the mill to that so it is supported at all sides.

Notwithstanding that the table is strong enough I'm worried about the
high center of gravity. If I bolt the table to the floor and the mill
to the table does that sound like a suitable arrangement?

Or should the mill be on a big heavy, long table?


How far does the table crank from side to side? Is this the
green mill-drill which showed up in another thread? I sometimes can't
keep the threads tied together.

Anyway -- since long workpieces are likely to be overhanging one
or the other end of the X-axis of the table, you want something to keep
it from toppling sideways. I would suggest getting steel tube
(rectangular or square) which extends say 18" to either side of the legs
on the table, and bolting it to both the front and rear legs so it will
prevent tipping. If you have to bolt it a bit above the floor to clear
the existing table's feet, add adjustable feet on the ends which you can
crank down to contact the floor. You probably won't have a load out to
the front of the mill which is enough to be a problem, so you don't need
extensions to the front and back which you could easily trip over.
Probably a good idea to paint them a bright yellow/orange so you see
them. :-)

Then there's tooling. I hope to buy some kind of lot assortment on
ebay. I looked tonight. A couple of guys are selling it saying
they're retiring. Of course I still don't know an end mill from a
collet.


You will learn -- and this approach, while it might not give you
everything you need, will get you started.

Tomorrow morning we're off to Wichita Falls to fetch the lathe.


Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
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Posts: 132
Default Electric motor on KBC mill

On Sep 30, 11:33*pm, "DoN. Nichols" wrote:
On 2008-10-01, Vernon wrote:

On Sep 30, 6:47*pm, David Lesher wrote:
"DoN. Nichols" writes:


* * * * [ ... discussion over whether this was too much information
* * * * * * * * snipped ... ]

Gentlemen,


Swamp away. *I may not understand it. But I want it. *All of it. *I am
a very studious fellow. *Sort of like a python swallowing a large
meal. *It may take a while but I'll get there...


* * * * Good approach.

Here's the critter I bought:


http://www.driveswarehouse.com/Drive...ess+Vector+VFD...


* * * * That one looks nice. *One thing which you should consider,
however, is where the metal chips will fly from your tools. *Set it up
so they won't get into those louvers in the sides, because it can get
exciting if they reach the circuitry. :-)

* * * * Simplest thing would be a wood frame around it with window
screening all around it, and some easy way to get inside if you need to
use the front panel controls. *This should keep the chips out, and let
air flow through to cool it.

* * * * If you're going to add a braking resistor (if you decide that
you *need* instant reverse), you want it to mount to metal, not wood, to
avoid fire. *In use those can get fairly hot.

I think I've figured out that both types of converter are in my
future. *The VFD shipped today. *It should get the bench mill running.


* * * * O.K.

Today I began taking inventory of some of the other 3 phase stuff I've
bought over the years. *What happened was this. *There was a time I
thought that getting 3 phase service to me was imminent. *Then the
electric company threw me a curve ball. *That's why I happen to have
this stuff.


* * * * I understand.

Among the items gathering dust is a Delta Unisaw (table saw). *It has
a 7.5 HP motor. *The freebie plenum box has a 7.5 HP motor.


* * * * O.K. *A bit marginal, and you may have to take the time to tune
it to make it start the saw reliably. *And you want the saw located as
far from the mill (and other machine tools) as possible. *Sawdust from
some woods is acidic and can cause rust where you don't want it.

Although I'm told it's good to have an idler motor that's a little
bigger than the load I hope to be able to roll my own rotary phase
converter from the motor in the plenum box.


* * * * Yes. *If you turn out to need a little more capability to start
the saw, hang another three phase motor on the RPC, start it after the
RPC is started, and it will help to start the saw.

* * * * * * * * * * * * * * * * * * * * * * *I will make the most
rudimentary thing possible.


* * * * That may or may not be sufficient for starting the saw. *Try it,
and if you have problems, add tuning and then an extra idler motor.

* * * * * * * * * * * * * * *Once I've determined that both motors run
I will attempt to finesse the thing into something more
sophisticated.


* * * * O.K. *You can probably test the idler motor (perhaps with the
fan removed) by driving it from the VFD.

* * * * * * * * It should help to have the mill up and running so that
I can make stuff for the project. *Of course I make that statement
pretending I have a clue about lathes and mills. *But I don't.


* * * * Hey -- I find that having a project in mind while learning a
tool (or a computer program) makes it easier to learn more and faster,
because you have something to hang what you read on. *Later, re-read wit
another project in mind, and you will pick up other things.

Nevertheless, I do have a modest library of books on the subject.
I've been mining ebay for years for old books that pre-date the
computer age. *At least several of these are encyclopedic manuals on
machining.


* * * * Great!

Here's a more basic question for your collective wisdom. *Where to
mount the mill? *I have a very heavy duty table that came as a base
for a Diacro single station hole punch. *The foot print of the table
is just a tad wider than the mill base. *But the base is just a tad
longer (1") than the table.


* * * * Hmm ... bolt some steel or thick aluminum plate to the table,
and then bolt the mill to that so it is supported at all sides.

Notwithstanding that the table is strong enough I'm worried about the
high center of gravity. *If I bolt the table to the floor and the mill
to the table does that sound like a suitable arrangement?


Or should the mill be on a big heavy, long table?


* * * * How far does the table crank from side to side? *Is this the
green mill-drill which showed up in another thread? *I sometimes can't
keep the threads tied together.

* * * * Anyway -- since long workpieces are likely to be overhanging one
or the other end of the X-axis of the table, you want something to keep
it from toppling sideways. *I would suggest getting steel tube
(rectangular or square) which extends say 18" to either side of the legs
on the table, and bolting it to both the front and rear legs so it will
prevent tipping. *If you have to bolt it a bit above the floor to clear
the existing table's feet, add adjustable feet on the ends which you can
crank down to contact the floor. *You probably won't have a load out to
the front of the mill which is enough to be a problem, so you don't need
extensions to the front and back which you could easily trip over.
Probably a good idea to paint them a bright yellow/orange so you see
them. :-)

Then there's tooling. *I hope to buy some kind of lot assortment on
ebay. *I looked tonight. *A couple of guys are selling it saying
they're retiring. *Of course I still don't know an end mill from a
collet.


* * * * You will learn -- and this approach, while it might not give you
everything you need, will get you started.

Tomorrow morning we're off to Wichita Falls to fetch the lathe.


* * * * Good Luck,
* * * * * * * * DoN.

--
*Email: * * | Voice (all times): (703) 938-4564
* * * * (too) near Washington D.C. |http://www.d-and-d.com/dnichols/DoN.html
* * * * * *--- Black Holes are where God is dividing by zero ---


" If you're going to add a braking resistor (if you decide that
you *need* instant reverse), you want it to mount to metal, not wood,
to
avoid fire. In use those can get fairly hot. "

Hey Don,

According to the on-line owner's manual for this and other Hitachi
VFDs, if I understood it correctly, they already have a programmable
instant reverse circuit. That section of the manual went pretty much
over my head. But at least the node is there. Apparently they
recommend you "try it" and if it's not fast enough recommend adding
another resistor.

Indeed, I did start two threads. One for the mill drill and the other
for the lathe / mill. I myself forget which one I'm in. But the mill
is a KBC brand. It is an old model Grip-16 visible on the
kbctools.com website under "mills". Takes an R8 collet. Oddly, mine
is painted "grizzly green". THe KBC guy stridently denied any
connection between KBC and Grizzly. The new ones, as seen in the KBC
catalog are a different color scheme.

The foot print of the mill is approximately 16" x 24". The narrow
dimension is the width. The Diacro punch press table I have is just a
little wider than the base of the mill. But the mill is a tad longer
front to back than. Nevertheless, both the base of the mill and the
feet of the table are drilled to something like 1/2". The point about
the table and work overhanging is a good one and well taken.

The tech support guy for the VFD seller tells me that lots of people
install the drives in the cabinet beneath the mill. I intend to duly
consider this. But I am definitely concerned about burs, chips and
dross falling into the innards. Of all the 3 phase albatrosses I have
around the one I'd most like to get going after the mill is a 48"
bandsaw. Following that I have an antique Lincoln 3 phase welder. It
is a DC generator welder spun by a 3 phase motor at the base. Looks
like a fire hydrant on wheels. Probably built in about 1943 or
something like that. I've been unable to discern the horsepower as
yet.

Thanks for everything.

V
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Default Electric motor on KBC mill

On Tue, 30 Sep 2008 19:38:16 -0700 (PDT), Vernon
wrote:

Today I began taking inventory of some of the other 3 phase stuff I've
bought over the years. What happened was this. There was a time I
thought that getting 3 phase service to me was imminent. Then the
electric company threw me a curve ball. That's why I happen to have
this stuff.


There are a few tricks you can still try - Are you in a single
family house with two or more stories and a handicapped occupant or
frequent visitor? Or one that wants to be a frequent visitor? Or a
small farm or rural property with a private water well? (And you're
willing to sink some serious money on an upgrade...)

For safety reasons you really need 3-Phase power to make sure that
larger well pump or elevator pump/traction motor always starts in the
right direction, you should have better luck getting real utility
3-phase for a Well Service or an Elevator Service - compared to "I
want to run big machine tools at my house" which you've already found
ranges from 'frowned upon' to 'Verboten!'

You just have to refrain from volunteering any information when they
ask why you need a 200A 3-Ph service for a 40A well pump or a 60A
elevator machine. You just say you got a great deal on a New Old
Stock (or used) 200A service that was far cheaper than a new 100A
service.

Memorize: "That's my story, and I'm sticking to it." Then wink.

(But allow the power company Service Planner to see what's hiding
under the tarps in the garage, they do have to make sure the service
transformer they place is big enough.)

And even then, it might take multiple tries to make it happen, as
you figure out ways to go around the roadblocks and find a sympathetic
ear at the County Building & Safety and Local Power Utility levels.

Never give up, Never give up that ship! ;-P Or the corollary:
"Always look on the bright side of life..."

-- Bruce --



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Default Electric motor on KBC mill

"DoN. Nichols" writes:


Yes. If you turn out to need a little more capability to start
the saw, hang another three phase motor on the RPC, start it after the
RPC is started, and it will help to start the saw.


I'm debating in my head if adding a flywheel to a RPC will improve its
ability to start big motors. I can generate arguments both way in my
head, but Machines 450 was 20+ years ago, and while I loved the class,
they say the mind is the first thing to go...



In one manner of thinking a VFD is just a special UPS. Years ago, I
worked at a company that made big 3 phase UPS's, as from the 10KW to 10MW
size.

These were ferroresonant UPS's. In mechanical terms, a FR system is a
transmission with a slip clutch and a big flywheel. You can lock the
output shaft, run it all day and nothing gets bothered. [You may know the
brand "Sola transformer"...]

In EE terms, they are short-circuit proof, and the FR 'tank' stablizes
the output across several cycles of line glitches.

A standard lab test for new designs involved a large 3 phase motor.
I recall it was ~4 ft diameter and 6+ long. No doubt it was surplus
from the steel mill.

You started the inverter module [Bigger units were usually collections
of 10KW modules...] up, and closed the breaker to the motor. Not much
happened; the humming got louder but that was it. If you looked at the
metering, you'd see the module was at 100% output power but so what, the
motor was still stopped.

Then, if you looked oh so closely, you could see it twitch and s l o w l y
turn a little and then more and ever so slowly it could be seen to be gaining speed....

Over 10-30 minutes, the motor would evenually come up to ~850 RPM, and the
current would drop to something normal. The module had passed..
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
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Default Electric motor on KBC mill

On 2008-10-01, Vernon wrote:
On Sep 30, 11:33*pm, "DoN. Nichols" wrote:


[ ... ]

* * * * Simplest thing would be a wood frame around it with window
screening all around it, and some easy way to get inside if you need to
use the front panel controls. *This should keep the chips out, and let
air flow through to cool it.

* * * * If you're going to add a braking resistor (if you decide that
you *need* instant reverse), you want it to mount to metal, not wood, to
avoid fire. *In use those can get fairly hot.


[ ... ]

* * * * * * * * * * * * * * *Once I've determined that both motors run
I will attempt to finesse the thing into something more
sophisticated.


* * * * O.K. *You can probably test the idler motor (perhaps with the
fan removed) by driving it from the VFD.


The consideration being that with the fan in place, it will
probably draw too much for the VFD to run it. But bare, with no load,
it can probably be spun up by a 3 HP VFD with no problems -- especially
if the VFD is set to a long acceleration time.

[ ... ]

Then there's tooling. *I hope to buy some kind of lot assortment on
ebay. *I looked tonight. *A couple of guys are selling it saying
they're retiring. *Of course I still don't know an end mill from a
collet.


* * * * You will learn -- and this approach, while it might not give you
everything you need, will get you started.


[ ... ]

Hey Don,

According to the on-line owner's manual for this and other Hitachi
VFDs, if I understood it correctly, they already have a programmable
instant reverse circuit. That section of the manual went pretty much
over my head. But at least the node is there. Apparently they
recommend you "try it" and if it's not fast enough recommend adding
another resistor.


Right. And the spindle of a mill is not nearly as massive a
thing to accelerate as the spindle of a lathe with a large chuck in
place, so the built-in resistor in the Hitachi should be sufficient,
unless you hang a big boring head on the spindle, and set it for the
highest speed -- probably a bad idea anyway, from the likely imbalance
of a boring head.

Indeed, I did start two threads. One for the mill drill and the other
for the lathe / mill. I myself forget which one I'm in. But the mill
is a KBC brand. It is an old model Grip-16 visible on the
kbctools.com website under "mills". Takes an R8 collet. Oddly, mine
is painted "grizzly green". THe KBC guy stridently denied any
connection between KBC and Grizzly. The new ones, as seen in the KBC
catalog are a different color scheme.


Well ... color schemes are easy to change -- just a different
requested color from the real manufacturers in Taiwan or China. :-) And
yours may have been from before Grizzly started selling metalworking
tools in addition to woodworking tools.

The foot print of the mill is approximately 16" x 24". The narrow
dimension is the width. The Diacro punch press table I have is just a
little wider than the base of the mill. But the mill is a tad longer
front to back than. Nevertheless, both the base of the mill and the
feet of the table are drilled to something like 1/2".


Hmm ... how strong a slab are you mounting it on? Is it thick
enough to accept drilling for anchors? If not, go for the outrigger
legs instead -- which will also make it easier to move things if you
decide to re-arrange the shop's layout.

The point about
the table and work overhanging is a good one and well taken.

The tech support guy for the VFD seller tells me that lots of people
install the drives in the cabinet beneath the mill. I intend to duly
consider this.


IIRC -- the cabinet in your case is an open frame table. But if
you mount a metal plate on the back for the power lines to go through,
and enclose the sides and front in window screening, it should keep the
chips clear, and allow airflow to keep the VFD cool. Obviously, plug or
tape over the holes in the top which have not been used to mount the
mill.

But I am definitely concerned about burs, chips and
dross falling into the innards. Of all the 3 phase albatrosses I have
around the one I'd most like to get going after the mill is a 48"
bandsaw.


A good choice. I wish that I had one of that size.

Following that I have an antique Lincoln 3 phase welder. It
is a DC generator welder spun by a 3 phase motor at the base. Looks
like a fire hydrant on wheels. Probably built in about 1943 or
something like that. I've been unable to discern the horsepower as
yet.


Hmm ... perhaps -- assuming that you don't use the welder near
full power rating -- you might be able to get away with a capacitor
start circuit like the Phase-O-Matic -- or like the auto starting
circuitry on a rotary converter.

If it is that old, the horsepower will probably be smaller than
you would expect for the size.

Can you find current and voltage specs on labels on the outside
of the device?

Good Luck,
DoN.

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Default Electric motor on KBC mill

On 2008-10-01, David Lesher wrote:
"DoN. Nichols" writes:


Yes. If you turn out to need a little more capability to start
the saw, hang another three phase motor on the RPC, start it after the
RPC is started, and it will help to start the saw.


I'm debating in my head if adding a flywheel to a RPC will improve its
ability to start big motors. I can generate arguments both way in my
head, but Machines 450 was 20+ years ago, and while I loved the class,
they say the mind is the first thing to go...


It has been considered here in the past -- but tests seem to say
that it does not help. It might prevent the RPC's idler reversing when
you try to "plug" reverse (that is switch the machine to reverse without
letting it slow to a stop first). Sometimes, when the idler in the RPC
is approximately the same HP rating as the load motor, and the load
motor is driving a lot of inertia, when you suddenly switch to reverse,
the idler motor reverses instead of the load motor -- allowing the
machine to keep on going into the crash which you were trying to avoid. :-)

In one manner of thinking a VFD is just a special UPS.


Without the extra power storage (normally lead-acid batteries)
which allows the UPS to keep providing power after the line power
vanishes. :-) But the output part is similar.

But the VFDs normally use PWM to simulate the output sine wave,
not a true sine wave (which you get out of the better UPS, since some
computer power supplies are allergic to the voltage spikes from a PWM
emulation of a sine wave.)

Years ago, I
worked at a company that made big 3 phase UPS's, as from the 10KW to 10MW
size.


Hmm ... Best Power Systems, by any chance? I really *like*
their USPs, and have three of them running at the moment -- all Ferrups
models.

These were ferroresonant UPS's. In mechanical terms, a FR system is a
transmission with a slip clutch and a big flywheel. You can lock the
output shaft, run it all day and nothing gets bothered. [You may know the
brand "Sola transformer"...]


Yep -- "Sola constant voltage transformer". I've also got a DC
power supply in which the only regulation is that it was built around a
Sola style transformer. Probably a bit more efficient than normal
linear regulators, but less so than a switching regulator.

In EE terms, they are short-circuit proof, and the FR 'tank' stablizes
the output across several cycles of line glitches.

A standard lab test for new designs involved a large 3 phase motor.
I recall it was ~4 ft diameter and 6+ long. No doubt it was surplus
from the steel mill.

You started the inverter module [Bigger units were usually collections
of 10KW modules...] up, and closed the breaker to the motor. Not much
happened; the humming got louder but that was it. If you looked at the
metering, you'd see the module was at 100% output power but so what, the
motor was still stopped.

Then, if you looked oh so closely, you could see it twitch and s l o w l y
turn a little and then more and ever so slowly it could be seen to be gaining speed....

Over 10-30 minutes, the motor would evenually come up to ~850 RPM, and the
current would drop to something normal. The module had passed..


Wow! *That* is impressive.

VFDs commonly start (from a full stop) by starting to output
something like 0.5 Hz (and an appropriately low voltage) and then
sweeping the frequency up to the full 60 Hz (here, or 50 Hz in the UK
and some other places). This allows control of the starting surge which
otherwise is present when a motor is simply just switched on. Most VFDs
have a parameter to control how long the ramp-up time is to keep from
drawing too much current and tripping the current limit error shutdown.
It can range from something like 0.1 second to several seconds.

Enjoy,
DoN.

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Default Electric motor on KBC mill

"DoN. Nichols" writes:


But the VFDs normally use PWM to simulate the output sine wave,
not a true sine wave (which you get out of the better UPS, since some
computer power supplies are allergic to the voltage spikes from a PWM
emulation of a sine wave.)


The ferro-resonant tank circuit was what gave you sine wave. Most
give a rotten waveform but they knew a thing or two about building
them.

Such came with a big price tag, however. Those custom-wound magnetics
were big heavy, noisy & expensive 30 years ago; today you could buy a
wall-street bank with 2 of them.

Years ago, I worked at a company that made big 3 phase UPS's, as from
the 10KW to 10MW size.


Hmm ... Best Power Systems, by any chance? I really *like* their USPs,
and have three of them running at the moment -- all Ferrups models.


Long since gone, I suspect -- Lorain Products, later p/o Reliance
Electric, LorTec and then who knows. [I see "LTI Power Systems"] They made
"Perpetuac" units as well as lesser ones.

Yep -- "Sola constant voltage transformer". I've also got a DC power
supply in which the only regulation is that it was built around a Sola
style transformer. Probably a bit more efficient than normal linear
regulators, but less so than a switching regulator.


VERY inefficient at anything but 100% load. A FR draws 30% of FL at 0%
out; they are great heaters. But they eat all kinds of line crap and
never blink. They will coast past a few missed cycles with no problem.


Over 10-30 minutes, the motor would eventually come up to ~850 RPM, and the
current would drop to something normal. The module had passed..


Wow! *That* is impressive.


Damn right.
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& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
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