Phase converter puzzle!

Ignoramus9179 · 2005-08-16T02:41:46+00:00

I built a self starting phase converter with a 10 HP idler and two 92mF capacitors. It works great and starts in under 2 seconds. I also have a very similar looking Century 7.5HP motor. They 10 HP and7.5 HP look similar.This 7.5 HP motor would NOT spin up from two other capacitors. If Iwire it with three capacitors (I have 5 total, 2 already used in themain phase converter), it would spin up, but it takes it about 5seconds to do so and it warms up appreciably. What gives?Another tidbit is that the 7.5 HP motor starts just fine from 3 phaseoutput of my phase converter. I do not think that it is a badmotor. Maybe some caps out of these three are in bad condition.i

Aug 16, 2005 22 Replies

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Robert Swinney 20 years ago

Agreed! Try the cap testing idea given by another RCM poster.

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Ignoramus4384 20 years ago

Yes, I will try that. I also ordered two new run rated caps from ebay.

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Jerry Martes 20 years ago

Think 9 volt "transistor battery". Thats enough DC for the solid state switch I use. I told you about this several months ago. I know the concept isnt too complex for you to have grasped. I think I have failed to be sufficiently clear with my communications. All thats needed ot build the RPC is a switch to connect the 220 single phase to the idler, and a start button to momrntarily insert a capacitor from the input single phase line to the unfed leg of the motor. A rotary phase converter with a1 HP idler will normally spin up an

*unloaded* 10 HP tool motor. That 10 HP tool motor will perform equally as well with that 1 HP idler as with true 3 phase whenever the tool is loaded to 5 HP or less.

Jerry

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