I recently bought a 3 phase 1 HP surface grinder. My original intention
was to replace the motor with a single phase unit. But the motor on the
grinder is closely integrated with the tool itself. I suspect that it
would be VERY expensive to take that approach.

So I'm looking at putting 3-phase power into the garage instead. Since
my shop is in my garage, I doubt that I could get the power company to
put in 3-phase power for any reasonable price. So I'm looking at
alternatives.

I ruled out static phase converters almost immediately.

But the choice between a rotary phase converter and a variable
frequency drive unit (VFD) isn't nearly so obvious. Each has good and
bad points - making the selection very difficult.

So, I'm asking you to help me choose. If you currently have or
previously had both types of units in your shop, which type would you
pick to power a 1 HP grinder?

A rotary built with used parts is certainly cheaper. If you don't need
to vary the speed, I'd go with the rotary. If speed control is useful
(lathe, mill) it becomes a toss up between function (VFD is NICE!) and
cost (VFD is usually consderably more expensive.

A grinder is one speed, go with the rotary.

wrote:
I recently bought a 3 phase 1 HP surface grinder. My original intention
was to replace the motor with a single phase unit. But the motor on the
grinder is closely integrated with the tool itself. I suspect that it
would be VERY expensive to take that approach.

So I'm looking at putting 3-phase power into the garage instead. Since
my shop is in my garage, I doubt that I could get the power company to
put in 3-phase power for any reasonable price. So I'm looking at
alternatives.

I ruled out static phase converters almost immediately.

But the choice between a rotary phase converter and a variable
frequency drive unit (VFD) isn't nearly so obvious. Each has good and
bad points - making the selection very difficult.

So, I'm asking you to help me choose. If you currently have or
previously had both types of units in your shop, which type would you
pick to power a 1 HP grinder?

wrote:
I recently bought a 3 phase 1 HP surface grinder. My original intention
was to replace the motor with a single phase unit. But the motor on the
grinder is closely integrated with the tool itself. I suspect that it
would be VERY expensive to take that approach.

So I'm looking at putting 3-phase power into the garage instead. Since
my shop is in my garage, I doubt that I could get the power company to
put in 3-phase power for any reasonable price. So I'm looking at
alternatives.

I ruled out static phase converters almost immediately.

But the choice between a rotary phase converter and a variable
frequency drive unit (VFD) isn't nearly so obvious. Each has good and
bad points - making the selection very difficult.

So, I'm asking you to help me choose. If you currently have or
previously had both types of units in your shop, which type would you
pick to power a 1 HP grinder?


1hp VFD for $100. To me it's a no-brainer.

On 23 May 2006 07:16:15 -0700, wrote:

I recently bought a 3 phase 1 HP surface grinder. My original intention
was to replace the motor with a single phase unit. But the motor on the
grinder is closely integrated with the tool itself. I suspect that it
would be VERY expensive to take that approach.

So I'm looking at putting 3-phase power into the garage instead. Since
my shop is in my garage, I doubt that I could get the power company to
put in 3-phase power for any reasonable price. So I'm looking at
alternatives.

I ruled out static phase converters almost immediately.

But the choice between a rotary phase converter and a variable
frequency drive unit (VFD) isn't nearly so obvious. Each has good and
bad points - making the selection very difficult.

So, I'm asking you to help me choose. If you currently have or
previously had both types of units in your shop, which type would you
pick to power a 1 HP grinder?

A cheaply and quickly made RPC out of a 3hp motor. Rope start is very
doable if you are on the cheap. Or a 1/4hp anything motor for a pony.

There was a gent selling an RPC panel on Ebay..simply add a motor. A
friend bought one and it works very very well. I think it was $99 or
something at the time..or $199..dont recall. I believe he was located
in California.

You can also use a VFD for this operation. 1hp units are not
particualy expensive. Just lock out ALL speed change options.
Depending on the unit..a tiny number have shown some harmonics on the
work piece..but I regularly use VFDs where finish is critical..and
note no issues with nearly all VFDs

Gunner

"If thy pride is sorely vexed when others disparage your offering, be
as lamb's wool is to cold rain and the Gore-tex of Odin's raiment
is to gull**** in the gale, for thy angst shall vex them not at
all. Yea, they shall scorn thee all the more. Rejoice in
sharing what you have to share without expectation of adoration,
knowing that sharing your treasure does not diminish your treasure
but enriches it."

- Onni 1:33

wrote:

I recently bought a 3 phase 1 HP surface grinder. My original intention
was to replace the motor with a single phase unit. But the motor on the
grinder is closely integrated with the tool itself. I suspect that it
would be VERY expensive to take that approach.

So I'm looking at putting 3-phase power into the garage instead. Since
my shop is in my garage, I doubt that I could get the power company to
put in 3-phase power for any reasonable price. So I'm looking at
alternatives.

I ruled out static phase converters almost immediately.

But the choice between a rotary phase converter and a variable
frequency drive unit (VFD) isn't nearly so obvious. Each has good and
bad points - making the selection very difficult.

So, I'm asking you to help me choose. If you currently have or
previously had both types of units in your shop, which type would you
pick to power a 1 HP grinder?


Precision grinders are no place to consider swapping motors, that motor is
likely optimized for smooth running, which translates directly into grinding
finish. The choice of VFD/convert is not just economics, there is also grinding
finish to consider. I have a small surface grinder which has newish spindle
bearings (maybe 10 hours on them) and which doesn't get stellar finishes, and I
have always wondered if my 3 phase power was to blame. I make mine from a
homebuilt phase converter, and it runs fine. VFDs of course deliver some
approximation to sinusoidal power, but I would wonder seriously about whether
you can get a good grind finish on a grinder powered by one.

Also, you can buy a VFD and wire it in and you're done, a phase converter is a
bigger project. So availability of your time is another variable.

If noise is a factor on a phase converter consider a remote idler motor, perhaps
located outside and wired through a wall.

GWE

I have a Thompson 12 x 24 ,5 horsepower surface grinder .I used a 10 hp
rotery phase
converter on it for years i could not get a good finish on it. I tried
every thing.I was about to get rid of the machine.And someone on this
group told me that on rotery phase converters
there phases may not be 120 deg. apart or something like that . There
for the motor would not run without vibration.I could not feel any
vibration. So i put a vfd on it ,single phase in 3 phase out and i now
get a mirror finish.For a surface grinder get a vfd.
Tim kallam
Kallam machine

http://groups.google.com/group/rec.c...7 92e074103b5

tim wrote:
I have a Thompson 12 x 24 ,5 horsepower surface grinder .I used a 10 hp
rotery phase
converter on it for years i could not get a good finish on it. I tried
every thing.I was about to get rid of the machine.And someone on this
group told me that on rotery phase converters
there phases may not be 120 deg. apart or something like that . There
for the motor would not run without vibration.I could not feel any
vibration. So i put a vfd on it ,single phase in 3 phase out and i now
get a mirror finish.For a surface grinder get a vfd.

Well, there you go! That gives me an excuse to wire up my VFD that's been
gathering dust! Actually, I don't really need a VFD for a grinder, just an
inverter (don't need variable frequency, 60Hz is fine).

GWE

wrote in message
oups.com...
I recently bought a 3 phase 1 HP surface grinder. My original intention
was to replace the motor with a single phase unit. But the motor on the
grinder is closely integrated with the tool itself. I suspect that it
would be VERY expensive to take that approach.

So I'm looking at putting 3-phase power into the garage instead. Since
my shop is in my garage, I doubt that I could get the power company to
put in 3-phase power for any reasonable price. So I'm looking at
alternatives.

I ruled out static phase converters almost immediately.

But the choice between a rotary phase converter and a variable
frequency drive unit (VFD) isn't nearly so obvious. Each has good and
bad points - making the selection very difficult.

So, I'm asking you to help me choose. If you currently have or
previously had both types of units in your shop, which type would you
pick to power a 1 HP grinder?

FWIW, I'm running an Hitachi L-100 VFD to power a 1 HP GE motor on my KO Lee
surface grinder and it runs fine and was easy to wire. The VFD was around
$250 (new) AIR, but to that I added a Hoffman enclosure, instrument relay
and diode, Square D fused disconnect, 220 VAC breaker (to the main CB box)
and a bit of wire and rigid and Liquitite conduit. That probably brought
the total to between $350 or $450. The point here is that there are often a
few (and sometimes many) gotchas in what it takes to get a job done.

The enclosure was to help keep grinding dust away from the VFD innards. The
instrument relay and diode was included so that the momentary on and off
switches on the grinder could be used to power it up and down, and the fused
disconnect because I don't like using a CB to power tools directly. A
contactor would probably have been better and may have eliminated the need
for the relay and dioide but I'm more comfortable specifying and installing
the disconnect box.

A rotary phase converter would probably have been cheaper but I was
attracted to the simplicity of the VFD, even though variable speed is likely
to be of little use on a surface grinder.

Mike

I installed a VFD in my garage a couple of decades ago an am VERY please
with it. I power my Bridgeport mill, Wilton geared-head drilling machine,
bench grinder, DoAll 26" bandsaw, and Clausing lathe with it. I use it at
full frequency output most of the time, but the ability to crank down the
speed for some operations like drilling large holes it very useful.

I think if you are patient and selective, you can pick up a used VFD for a
very reasonable price. Can't say that I remember what I paid for my VFD,
but I think it was in the neighborhood of $100 or $200. It was new surplus
and rated at 2HP, I think. Don't be too conservative in your power rating
selection. One of the great advantages of having 3-phase power available is
that you can bid on machines at auction that many guys have to pass up due
to power issues. I highly recommend the VFD. I have no experience with a
rotary converter.

awright

wrote in message
oups.com...
I recently bought a 3 phase 1 HP surface grinder. My original intention
was to replace the motor with a single phase unit. But the motor on the
grinder is closely integrated with the tool itself. I suspect that it
would be VERY expensive to take that approach.

So I'm looking at putting 3-phase power into the garage instead. Since
my shop is in my garage, I doubt that I could get the power company to
put in 3-phase power for any reasonable price. So I'm looking at
alternatives.

I ruled out static phase converters almost immediately.

But the choice between a rotary phase converter and a variable
frequency drive unit (VFD) isn't nearly so obvious. Each has good and
bad points - making the selection very difficult.

So, I'm asking you to help me choose. If you currently have or
previously had both types of units in your shop, which type would you
pick to power a 1 HP grinder?

I've done both, they both work well.

The two big issues from my viewpoint:
A VFD gives you variable speed, which can be a nice thing.
Only some VFD's will deal well with mechanical switching between the VFD
and the motor. This makes it a pain in the rear to have multiple
machines on a single VFD. RPC's have no such problem.

Steve

wrote:

I recently bought a 3 phase 1 HP surface grinder. My original intention
was to replace the motor with a single phase unit. But the motor on the
grinder is closely integrated with the tool itself. I suspect that it
would be VERY expensive to take that approach.

So I'm looking at putting 3-phase power into the garage instead. Since
my shop is in my garage, I doubt that I could get the power company to
put in 3-phase power for any reasonable price. So I'm looking at
alternatives.

I ruled out static phase converters almost immediately.

But the choice between a rotary phase converter and a variable
frequency drive unit (VFD) isn't nearly so obvious. Each has good and
bad points - making the selection very difficult.

So, I'm asking you to help me choose. If you currently have or
previously had both types of units in your shop, which type would you
pick to power a 1 HP grinder?

I've looked for the elusive $100 VFD but I can't find anything for even
close to that price. Please point me in the right direction.


Gary

wrote:

I've looked for the elusive $100 VFD but I can't find anything for even
close to that price. Please point me in the right direction.

I've paid $100 direct from these guys,
I see it's $120 via ebay.

http://cgi.ebay.com/HITACHI-Inverter...cmdZViewIte m

Here is where i buy my vfd,s best prices i have found and there new.
http://web3.automationdirect.com/adc/Shopping/Catalog/AC_Drives_-z-_Motors/GS1_(120_-z-_230_VAC_V-z-Hz_Control)

According to RoyJ :
A rotary built with used parts is certainly cheaper. If you don't need
to vary the speed, I'd go with the rotary. If speed control is useful
(lathe, mill) it becomes a toss up between function (VFD is NICE!) and
cost (VFD is usually consderably more expensive.

A grinder is one speed, go with the rotary.

But -- you want to take care to properly balance the legs of the
rotary converter. The grinder will *run* anyway, but the torque ripples
show up in the surface when grinding with single phase, or with
unbalanced three phase.

The VFD would assure proper balance anyway.

It is good that the design of your surface grinder kept you from
swapping in a single-phase motor. You would have regretted it (after
you finally started to ask questions about surface finish problem. :-)

To my mind, the choice point between a VFD and a rotary
converter is whether you have multiple machines needing three phase, or
expect to have that. If so -- then a larger rotary converter could
power the whole shop. For any machines which could benefit from
variable speed (which can include larger drill presses as well as lathes
and mills), individual VFDs on a per-machine basis will allow tuning the
speed without having to worry about the effect on other machines which
might be running at the same time -- and will allow you to mount the
speed controls were they will be easy to access from the machine which
they control.

And besides that -- you really don't want to switch the power at
some point between the VFD and the motor -- that can lead to rather
early failure of the output transistors, unless the VFD is massively
oversized for the motor, as in the case of the 7-1/2 HP VFD which
happens to be running my Nichols mill with only a 1 HP motor. :-)

Enjoy,
DoN.
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