# 10 Hp Rotary Phase Converter



## Martin W (Apr 23, 2016)

Hi all,
Will a 10 hp rotary phase converter run a 10 hp motor? I know you are supposed to have a larger phase converter for your largest motor you are running.And for the starting load of the motor. E.g. 10hp to run a 5 hp . 
Could it possibly work? Without finding a 15 hp
Martin



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## Ulma Doctor (Apr 23, 2016)

the short answer is, yes- a 10 hp RPC will run a 10 hp motor with limitations


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## Ed ke6bnl (Apr 23, 2016)

my guess it will work, because it starts with a low load and you may never use the full capacity load of the machine. May not work for an air compressor of 10 hp. BUT lets hear from those who no best. I have made one from scratch and made them from ebay phase converters all working fine.


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## Scruffy (Apr 23, 2016)

I purchased a control panel from phase-craft,. It's for a 15 hp motor I had. I have ran my10 hp lathe and 5 hp mill at the same time several times with no problems.
Thanks ron


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## Martin W (Apr 23, 2016)

Thanks. I was thinking it would be okay with limitations. Just wanted second opinions.
Martin


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## Reeltor (Apr 23, 2016)

You shouldn't have any problems.  If you do have an issue starting a 10hp machine motor, just start another smaller machine first.  It's like adding another pony motor to the RPC.  Then start the 10hp machine, after this motor is up to speed you can shut off the smaller machine.

I always thought, that a RPC can start a motor of equal power of the RPC, it's the static converters where you loose about 1/3 to 1/2 the hp of the static converter.


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## Ulma Doctor (Apr 24, 2016)

starting the 10 hp from the RPC will be easy, the problem may come if you use all of the amps supplied by the breaker during hard operation.
you may wish to put the RPC on a 50 amp breaker to alleviate potential problems


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## master53yoda (Apr 24, 2016)

Rotary converters can supply 2/3 of the full load amps X the service factor on convertor.  If you try to run more than that you are generating excess heat in the winding that is connected to the single phase power supply.     a 10 hp convertor will not live if running a 10 hp motor at FULL  LOAD.

An electric motor only delivers the HP that the load is requiring.   Most machines use less than 1/2 of the rated HP of the motors unless making very large cuts.   If you are pushing the convertor it will make definite load noises and dim lights etc.

In our shop we have a 30 hp output convertor (50 hp Motor) feeding a 40 hp Hass CNC mill and a 20 hp Hass CNC Lathe at the same time.   The convertor full load is 98Amps  the highest I have ever seen it draw was 60+ for a short period when doing a large cut in the mill.    It is unlikely that you will have a problem, if you are in doubt put a amp-meter on the incoming  single phase line and monitor it, don't let it run over full load for any extended period of time (5 min)

Art B


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## JimDawson (Apr 24, 2016)

This is a timely thread.  In a few weeks I will be installing a RPC to run a CNC router with a 10HP spindle motor for a customer.  From what I am reading here it sounds like a 15HP RPC is what is needed to have a reasonable safety factor.  I suspect that the spindle will almost never require anywhere close to it's rated power, but my biggest concern is that the RPC plays nice with the controls.

Any thoughts?


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## Ulma Doctor (Apr 24, 2016)

JimDawson said:


> This is a timely thread.  In a few weeks I will be installing a RPC to run a CNC router with a 10HP spindle motor for a customer.  From what I am reading here it sounds like a 15HP RPC is what is needed to have a reasonable safety factor.  I suspect that the spindle will almost never require anywhere close to it's rated power, but my biggest concern is that the RPC plays nice with the controls.
> 
> Any thoughts?



as long as you use 2 non generated hot legs for making the CNC power supply connections you should be ok.


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## JimDawson (Apr 24, 2016)

Thanks Mike!


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## Keith Foor (May 2, 2016)

Couple of things to know / remember.  phase converter idler motors will combine with other motors on the load side to increase their capacity.  IE if you have a 10hp converter and then start a 5 hp motor the total size of the converter is 15 HP.  Friend of mine sets up farm grain systems and had built 100 HP RPC systems out of multiple 25 HP motors because starting a single 100 HP motor is about impossible with capacitor start.  

BUT, keep in mind that it ONLY applies to direct feed 3 phase motors.  If you are running a whiz bang, CNC lathe with a 10 hp DC or electronically controlled motor, it doesn't add to the capacity, it subtracts from it.  The converter works as a tuned circuit with the inductance of the winding's of the motor and the capacitance added across it.  If a motor is beyond some type of electronic controller, the load is pretty much resistive and does not contribute any meaningful amount of inductance to the RPC system.  

Another thing to consider is if there will be a device that has a 3 phase motor running on the RPC that will be more or less always on if the RPC is running.  I am wood shop this would be something like a dust collection blower.  When you are designing your RPC and setting up the run capacitors for the inductance of the motors,  make sure that you are running both the RPC and the device that will be always on when doing leg to leg voltage checks for tuning the values of the run capacitors.  This increases the sizing of the RPC system as well and will give it a larger start capacity than doing the caps for just the pony motor.  Again this ONLY applies to motors that are connected through a simple switch or contactor and not an electronic controller.


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## Reeltor (May 2, 2016)

Here is a YouTube video from Keith Rucker of VintageMachinery.org on how he is wiring his shop and using a RPC instead of VFD's.





Mike


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## nitro96 (Sep 20, 2016)

i have three 3 phase machines.I use a heavy duty phase a matic converter 8-12 hp to start a 10 hp 3 phase motor behind the shop.once the 10 hp motor starts and the phase a matic buzzes i turn off the phase a matic and then have a panel boxe with breakers for each machine. my lathe is 7 hp so the 10 horse out back runs her at full power.i just run one machine at the time anyways.I had a electrician do the job so its all good,and works very well for me.
	

		
			
		

		
	



	

		
			
		

		
	
 please disregard the cable wires. Chris


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