# Rotary Phase Converter Question



## Brain Coral (Mar 27, 2014)

Hello all,

I have an Elimia 5 hp rotary phase converter and was talking about it to my machinist friend recently. He claims that once the idler motor has started and the start caps have have kicked out, it then produces its own power, like a generator, and the only household power that it is using while running, is the 110 volts to the light in the on/ off switch.

Is this correct ?

Brian


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## Alan Douglas (Mar 27, 2014)

Only if it's not supplying another 3-phase motor on a machine. And even if it's just idling, the idler motor itself takes a small amount of power to overcome friction, windage, and electrical losses in the iron.

If it's supplying the third phase to run another machine, that power of course comes from the household power.  It would be perpetual motion otherwise.


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## John Hasler (Mar 27, 2014)

Brain Coral said:


> Hello all,
> 
> I have an Elimia 5 hp rotary phase converter and was talking about it to my machinist friend recently. He claims that once the idler motor has started and the start caps have have kicked out, it then produces its own power, like a generator, and the only household power that it is using while running, is the 110 volts to the light in the on/ off switch.
> 
> ...



No.  It does generate power on the high leg but it uses power coming in from the single phase to do it.    All the three phase power coming out of a converter came in as single phase.


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## Brain Coral (Mar 27, 2014)

Thank you Allan. That makes sense to me. I found it hard to believe that it didn't use household power, but for the little light bulb in the switch, while running and supplying power to my mill or lathe.

Brian


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## Ulma Doctor (Mar 27, 2014)

the third leg is created by induction .


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## rdhem2 (Mar 28, 2014)

What is *windage* as a loss in a motor circuit?


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## Ray C (Mar 29, 2014)

rdhem2 said:


> What is *windage* as a loss in a motor circuit?



I believe it's in reference to wind resistance from the spinning rotor or possibly the cooling fan (if so equipped).  A highly refined rotor is aerodynamically designed to cool itself just from the air circulation without creating excessive wind drag.  The motors probably run quieter...  I don't know off-hand in what applications it makes sense to account for these things but I do recall hearing about motor designs that incorporate such design considerations.

Ray


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## Alan Douglas (Mar 29, 2014)

Of course it's normally negligible but the original poster had been told it was zero.


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## hvontres (Mar 29, 2014)

rdhem2 said:


> What is *windage* as a loss in a motor circuit?



As I recall from my classes two decades ago, we always had a term for Friction and Windage losses. I think that that referes to all of the mechanical ways to create excess entropy while running your motor.  But I don't remember ever accounting just for windage lossses.


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## Ray C (Mar 29, 2014)

A good rule of thumb...  If it gets warm, it's consuming energy.  If it produces cold, it's consuming energy.  If it's exactly at room temperature, it's not plugged in.


Ray


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## rdhem2 (Mar 29, 2014)

Once more Ray C. nails the problem like a pro.  _WHAM!!!!!!!!!!!     _*No messing around.     *:roflmao:


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