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Old January 21st 06, 07:51 PM posted to rec.crafts.metalworking
Mark Main
 
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Default VFD used with either a 3~ Rotary Converter or Phase Inverter

I'm a newbie who's trying hard to do my research before simply
asking the dumb newbie questions; despite my efforts I still need to
helpful coaching.

Here are my 3 key goals:
1. Using a 5 or 10HP 3~ motor, I want to control the full 40-4000 RPM
range of a Monarch 10EE directly from the machine, without swapping
belts, and with minimal torque loss/variance; and possibly increase the
RPM to 4500 or 5000.
2. I want to convert/provide 3~ power throughout my shop from my
standard 1~ grid power.
3. I want to be able to run 1 or more 3~ machines at a time up to a
combined maximum of 10 or 15 HP, and to control their RPM speed
directly on each machine.

STEP 1: SAFELY/CONVENENTLY PROVIDE 3~ SHOP POWER

The two best shop options seem to be a Rotary Converter or Phase
Inverter.

ROTARY CONVERTER
If I build one myself here is what sounds like the best recommendations
I've read (please let me know if you disagree or have any other
suggestions):

1. Size the idle motor 1.5x my maximum HP needed (e.g. 15HP x 1.5 =
22.5 HP+).
2. Automatically power the converter with the shop lights or with a
sensor detecting that power is desired by a machine. Power should be
turned off automatically with a drop in grid power, when the shop
lights are turned off, and possibly after a certain delay from non-use
(e.g. 30-minutes).
3. Automatically self-start the idle motor by compromising (staggering)
the capacities of the tuning capacitors during the startup process, and
then once running, relays can engage additional capacitors to restore
balanced capacitor capacity ("tuning") between the 3 phases, in
order to optimize the balance of voltage/current in the generated phase
to match the other two phases. BTW, I really would like to learn more
about this in greater detail.
4. After the tuning has taken place, I've read that you can also add
a power-factor correction capacitor across the line power leads coming
into the converter to minimize any out-of-phase current flow into the
idler motor. This apparently should not affect your home electricity
costs, but will probably affect commercial rates. Also, it is important
to note that this can trip circuit breakers if you become close to the
maximum rating. I would like to learn more about this from 'DoN.
Nichols' (who first wrote about it) or others if possible.

PHASE INVERTER

I've not read much about this other than I know that a modified sine
wave is more accurate, but it I don't know if that really matters to
a motor. Are phase inverters more expensive than building your own
rotary converter? What are some good sources?

STEP 2: SAFELY/CONVENENTLY VARY MACHINE SPEED WITHOUT TORQUE LOSS

It sounds like the preferred option, using the latest technology
available today, seems to be VFD (variable frequency drives). Most
people use a single VFD to control power for the entire shop and locate
this near (or on) the machine that would most benefit from having
variable speed control nearby.

If I want to have this convenience on every machine then it appears I
will need to purchase a VFD for each machine rate at the power for that
particular machine.

Am I wrong with my understanding? Is there a better way to adjust the
RPM for the full range of the Monarch 10EE without severe torque
impact?

Can I modify a 4000 RPM rated machine to run a 4500 or 5000 RPM?

What are great sources for new or used VFD's?

Thanks to all in advance for your help.


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Old January 21st 06, 08:19 PM posted to rec.crafts.metalworking
Don Foreman
 
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Default VFD used with either a 3~ Rotary Converter or Phase Inverter

On 21 Jan 2006 11:51:23 -0800, "Mark Main" wrote:


Am I wrong with my understanding? Is there a better way to adjust the
RPM for the full range of the Monarch 10EE without severe torque
impact?


Bear in mind that when you change pulleys or gear ratios, you
increase available torque when you reduce output speed. A VFD does
not do this. The torque an induction motor can deliver does not
increase when speed is reduced by reducing drive frequency.

  #3   Report Post  
Old January 22nd 06, 01:15 AM posted to rec.crafts.metalworking
Karl Townsend
 
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Default VFD used with either a 3~ Rotary Converter or Phase Inverter


"Don Foreman" wrote in message
...
On 21 Jan 2006 11:51:23 -0800, "Mark Main" wrote:


Am I wrong with my understanding? Is there a better way to adjust the
RPM for the full range of the Monarch 10EE without severe torque
impact?


Bear in mind that when you change pulleys or gear ratios, you
increase available torque when you reduce output speed. A VFD does
not do this. The torque an induction motor can deliver does not
increase when speed is reduced by reducing drive frequency.


A proven design for the 10EE is to use a VFD and 10 HP motor. No need for
backgear (lower gear) if you go this route. You can run a VFD off single
phase if you oversize it. In this case a 15 hp. VFD would run your 10 hp.
motor. Belt your unit so that you get max RPM at two times motor nominal
speed. For example a 1750 motor will go 3500 RPM top end with a VFD. You'll
need to step it up a bit if you want 5000 at the spindle for example.

You have to be careful that you don't buy a VFD that senses for all three
phases present. I bought a Hitachi S300 and found out I couldn't use it. But
the Hitachi S100 doesn't test for three phase. I'm using a 10 hp unit to run
my 7 1/2 hp. lathe. I bought from Automation Direct web site.

I used the back gear on my Monarch 10 EE. I already had it on the machine.
Then I could use a 5 hp motor and 7 1/2 hp. VFD. WAY LESS BUCKS!

For your other queries. look up a web site "Metal Web News" There's a huge
section on 3 phase build your own converters.

Karl







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Old January 22nd 06, 04:58 PM posted to rec.crafts.metalworking
Mark Main
 
Posts: n/a
Default VFD used with either a 3~ Rotary Converter or Phase Inverter

You can run a VFD off single phase if you oversize it. In this case a 15 hp. VFD would run your 10 hp. motor.
You have to be careful that you don't buy a VFD that senses for all three phases present.


I've been reading that providing "tuned" 3~ power using a rotary
coverter will product slightly smother lathe results than making the 3~
motor work on 1~ power. It makes sense in theory, but I have no
experience to know if the theoretical is actually noticable in the
final product. For that matter, I've read that 3~ motors are slightly
better for lathes than 1~ for the same reason.

I would like to have the 5K RPM and so that will require a 1:2.86 belt
ratio rather than the 1:2 in your example. If I decide to go this
route, won't I really need a 3~ 15HP motor with full 3~ power to keep
in spec with the 10HP @ 3000 RPM example you gave?

I really like the idea of compromising (staggering) capacitors for the
self-start idle motor during the startup process. If anyone has some
suggestion details please let me know, otherwise I'll post pictures on
my "how to" after my painful trial and error period (probably this
spring or summer).

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Old January 22nd 06, 10:51 PM posted to rec.crafts.metalworking
Robert Swinney
 
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Default VFD used with either a 3~ Rotary Converter or Phase Inverter

If you opt for a rotary phase converter just remember the idler motor /
total load ratio of 1.5 X is on the low end. A reasonably larger sized
idler won't be a problem but you will probably have to consider a pony motor
for starting. It is usu. recommemded that idlers of 10 HP and larger be
started with a pony to reduce "start-up" current surge.

Bob Swinney

"Mark Main" wrote in message
oups.com...
You can run a VFD off single phase if you oversize it. In this case a 15
hp. VFD would run your 10 hp. motor.
You have to be careful that you don't buy a VFD that senses for all three
phases present.


I've been reading that providing "tuned" 3~ power using a rotary
coverter will product slightly smother lathe results than making the 3~
motor work on 1~ power. It makes sense in theory, but I have no
experience to know if the theoretical is actually noticable in the
final product. For that matter, I've read that 3~ motors are slightly
better for lathes than 1~ for the same reason.

I would like to have the 5K RPM and so that will require a 1:2.86 belt
ratio rather than the 1:2 in your example. If I decide to go this
route, won't I really need a 3~ 15HP motor with full 3~ power to keep
in spec with the 10HP @ 3000 RPM example you gave?

I really like the idea of compromising (staggering) capacitors for the
self-start idle motor during the startup process. If anyone has some
suggestion details please let me know, otherwise I'll post pictures on
my "how to" after my painful trial and error period (probably this
spring or summer).





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Old January 23rd 06, 08:26 PM posted to rec.crafts.metalworking
Mark Main
 
Posts: n/a
Default VFD used with either a 3~ Rotary Converter or Phase Inverter

Thanks Bob. I was doing some more reading and found the recommendation
of 2X max load being a better minimum size for the idle (converter)
motor. I've trying to find a 40 HP 220/240V 16 pole (450 RPM) motor
(or an 8 pole/900 RPM if I can't find the slower). Is it possible for
me to oversize the starting capacitors enough to avoid the pony motor?
If not, any suggestions on how to automatically engage the pony during
startup and then disengage it once stated?

Also, I was considering powering a small fan to cool down the enclosure
and motor. If I use the idle motor to power the fan, is that going to
be a problem so long as I keep the blade size small (e.g. 3" - 6")? I
was thinking of rigging up some kind of furnace filter type setup to
allow air to flow into the enclosure; I'd place some kind of metal
protection that allows the filtered air to pass through, but still keep
hands away from reaching inside when the filter is removed.

It seems that it will be more cost effective to make a nice 3 phase
converter even if I decide to go with a VFD later on. It seems that
oversizing a 3 phase converter is much cheaper than oversizing several
3 phase VFD's to run on 1 phase power. This is of interest to me
because I could see myself adding a VFD to several machines... I really
don't want to have a single VFD running the whole shop--it's a
convenience thing.

Please let me know if my cost analysis is incorrect. Thanks.

  #7   Report Post  
Old January 23rd 06, 08:52 PM posted to rec.crafts.metalworking
Robert Swinney
 
Posts: n/a
Default VFD used with either a 3~ Rotary Converter or Phase Inverter


"Mark Main" wrote in message
oups.com...
Thanks Bob. I was doing some more reading and found the recommendation
of 2X max load being a better minimum size for the idle (converter)
motor. I've trying to find a 40 HP 220/240V 16 pole (450 RPM) motor
(or an 8 pole/900 RPM if I can't find the slower). Is it possible for
me to oversize the starting capacitors enough to avoid the pony motor?
If not, any suggestions on how to automatically engage the pony during
startup and then disengage it once stated?


Why are you looking for an 8 or 16 pole idler motor? Generally, idler
motors are made from 4 pole or 2 pole motors which are the most common and
least expensive. The number of poles in the respective load motors will
determine their speed, i.e. they will run near their "synchronous speed",
what ever that may.
It may be possible to start a 10 HP, or so, idler with capacitors but I
think starting a 40 HP motor with capacitors alone is out of the question.
Someone on RCM a while back said he was starting a 15 HP idler with no
problems.

Bob Swinney


enclosure
and motor. If I use the idle motor to power the fan, is that going to
be a problem so long as I keep the blade size small (e.g. 3" - 6")? I
was thinking of rigging up some kind of furnace filter type setup to
allow air to flow into the enclosure; I'd place some kind of metal
protection that allows the filtered air to pass through, but still keep
hands away from reaching inside when the filter is removed.

It seems that it will be more cost effective to make a nice 3 phase
converter even if I decide to go with a VFD later on. It seems that
oversizing a 3 phase converter is much cheaper than oversizing several
3 phase VFD's to run on 1 phase power. This is of interest to me
because I could see myself adding a VFD to several machines... I really
don't want to have a single VFD running the whole shop--it's a
convenience thing.

Please let me know if my cost analysis is incorrect. Thanks.



  #8   Report Post  
Old January 23rd 06, 11:36 PM posted to rec.crafts.metalworking
Mike Berger
 
Posts: n/a
Default VFD used with either a 3~ Rotary Converter or Phase Inverter

That's true for a VFD too. Both Danfoss and Mitshbishi suggested
derating by 50% for single phase use.

Robert Swinney wrote:
If you opt for a rotary phase converter just remember the idler motor /
total load ratio of 1.5 X is on the low end. A reasonably larger sized
idler won't be a problem but you will probably have to consider a pony motor
for starting. It is usu. recommemded that idlers of 10 HP and larger be
started with a pony to reduce "start-up" current surge.

  #9   Report Post  
Old January 24th 06, 03:07 AM posted to rec.crafts.metalworking
Mark Main
 
Posts: n/a
Default VFD used with either a 3~ Rotary Converter or Phase Inverter

Why are you looking for an 8 or 16 pole idler motor?

My goal is to have 20 HP available and so I sized my idle motor at 2
times that; and it appeared from my reading that more poles would have
the advantage of easier start and slightly improved stability for the
3-phase power. If I'm wrong let me know. My hope is that 8 or 16
poles on a 40 HP will make starting difficulty closer to a 10 or 15 HP
2 or 4 poles.

It may be possible to start a 10 HP, or so, idler with capacitors but I think starting a 40 HP motor with capacitors alone is out of the question. Someone on RCM a while back said he was starting a 15 HP idler with no problems.


Yeah, I'll probably have to go with the pony motor. If I can actually
find a 16 pole motor then it will be interesting to play with it to see
if I can get it going with larger capacitors. I'd like to avoid the
pony motor if possible...I can be stubborn when I have a goal in mind.
g probably a trait shared by many who play with metals.

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Old January 24th 06, 04:36 AM posted to rec.crafts.metalworking
 
Posts: n/a
Default VFD used with either a 3~ Rotary Converter or Phase Inverter


Mark Main wrote:
Why are you looking for an 8 or 16 pole idler motor?


My goal is to have 20 HP available and so I sized my idle motor at 2
times that; and it appeared from my reading that more poles would have
the advantage of easier start and slightly improved stability for the
3-phase power. If I'm wrong let me know. My hope is that 8 or 16
poles on a 40 HP will make starting difficulty closer to a 10 or 15 HP
2 or 4 poles.

It may be possible to start a 10 HP, or so, idler with capacitors but I think starting a 40 HP motor with capacitors alone is out of the question. Someone on RCM a while back said he was starting a 15 HP idler with no problems.


Yeah, I'll probably have to go with the pony motor. If I can actually
find a 16 pole motor then it will be interesting to play with it to see
if I can get it going with larger capacitors. I'd like to avoid the
pony motor if possible...I can be stubborn when I have a goal in mind.
g probably a trait shared by many who play with metals.


I've used a 30 HP RPC for years, and always started it on just the
capacitors. It was a 4 pole (1750 rpm) motor. It was fed from a 240V
100 amp panel. No problems for me.
I don't see why you need anything more than a 4 pole motor. Unless you
have a big grudge against your wallet.
No pony motor, Just about 2000 MFD to start. THUMP!. Running. Cut
metal.
Pete



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