# Selecting a 3 phase motor for RPC set up.  Which HP?



## RRT (Jun 19, 2012)

I have a 1 HP 3 phase power hacksaw.  I have several 3 phase motors to choose from.  1/2 hp to 3 HP.  Maybe higher if I dig some more.  Is it best to match HP?    Thanks.


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## Hawkeye (Jun 19, 2012)

Everything I've heard about RPCs says that you lose some capacity from the supply motor. That would suggest that you use the 3 hp to generate 3-phase for the 1 hp. They both need to be the same voltage and frequency ratings.


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## SamIAm (Jun 20, 2012)

RRT said:


> I have a 1 HP 3 phase power hacksaw.  I have several 3 phase motors to choose from.  1/2 hp to 3 HP.  Maybe higher if I dig some more.  Is it best to match HP?    Thanks.



RRT,
is your 1hp motor failing? or are you wanting to try to do a motor swap for some other reason?
On a direct 3Ph setup you can put what ever you like since the motor is 3Ph and the incoming line is 3Ph. 
example: if you had a 220 setup. the 220 doesn't care what you put on it and neither will the 3Ph. however as you go up in Hp 
so will the amperage draw. a supply cable or breaker change might be in order. 

However if your using a VDF driver. then first I would consult the manual for your particular device. but in general I would say
its ok to go =< the rated Hp for such device but never more than.

Then you have the equipment. I would also say if the equipment was engineered correctly. the motor that ships with it 
should be the telltale for the targeted/desirable Hp. 

best!
Sam


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## RRT (Jun 20, 2012)

TheSniper said:


> RRT,
> is your 1hp motor failing? or are you wanting to try to do a motor swap for some other reason?
> On a direct 3Ph setup you can put what ever you like since the motor is 3Ph and the incoming line is 3Ph.
> example: if you had a 220 setup. the 220 doesn't care what you put on it and neither will the 3Ph. however as you go up in Hp
> ...



Sorry Sam I should have been clearer.  I am not changing the motor on the power hack.  I was trying to determine the best HP for the extra 3 phase motor used in converting single phase 220 to 3 phase for the power hack.   Oh, and I would love to have a manual for that old monster.
Thanks


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## SamIAm (Jun 20, 2012)

RRT said:


> I have a 1 HP 3 phase power hacksaw.  I have several 3 phase motors to choose from.  1/2 hp to 3 HP.  Maybe higher if I dig some more.  Is it best to match HP?    Thanks.



Here you have "several" 3 phase motors...




			
				RRT;60793 I am not changing the motor on the power hack. I was trying to determine the best HP for the extra 3 phase motor used in converting single phase 220 to 3 phase for the power hack. Oh said:
			
		

> RRT,
> 
> Sorry, Im a little confused... you also say your "not changing the motor".
> 
> ...


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## Kennyd (Jun 20, 2012)

Use the largest one you can get-in this case the 3HP one.  That way you can use the RPC for future purchases as well.  There is no need to "match" the RPC to the tool it powers, as long as the RPC is rated higher you will be fine.


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## Kennyd (Jun 20, 2012)

TheSniper said:


> Here you have "several" 3 phase motors...
> 
> 
> 
> ...




Sam, he wants to build a RPC...and is asking what motor to use.


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## RRT (Jun 21, 2012)

A 3 HP it will be.  Thanks guys.


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## SamIAm (Jun 21, 2012)

Kennyd said:


> Sam, he wants to build a RPC...and is asking what motor to use.



Ahh got it...thx
Btw just seen you Clausing lathe rebuild... hats off to that!:tiphat: it sure is sweet!


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## Philco (Jun 27, 2012)

I'm pretty sure the ratio is 1.5 times the largest motor that you planninng on running. Example:    5hp machine motor x 1.5= 7.5 hp phase converter. In you're case, 3hp phase converter would be plenty to run the saw but it want run anything over 2hp. Hope this helps.


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