Originally Posted by
Rick Christopherson
No. You are still thinking like an RF engineer. The size of the capacitor is not the primary dictater in the current, but it is dictating how far out of phase the current is. If you don't shift the current in the start circuit, you don't get a start. If you don't shift it enough, you don't get a start. It doesn't matter if you gave the starting circuit full line power--if the phase shift is not present, the motor will not start and you will smoke the start winding.
If all you needed to do was limit the amperage in the start circuit, you could do that resistively. The function is phase shift, and I can't seem to stress that quite enough.
I know what you are saying here, however, I could convince a layman with a few sentences, but to re-educate an engineer would take volumes. I don't have time to do that. That is what text books are for. I don't mean that in a disrespectful way, but we both know how deep the discussion would have to delve in order to accomplish that task.
I can assure you, Rick, that I understand the need to have a phase shift in the starter circuit.
And I have motor theory textbooks (modern editions, not my old college ones) which I've reviewed recently because of the discussions on this forum (do you really think I could have remembered all this stuff from 40+ years ago?). I am quite willing to stand by the accuracy of what I've posted. If you, or someone else, can post a good valid argument against what I've posted, I'll change my mind. But the argument has to be stated in terms of the theory of operation of an induction motor and not just old wives tales.
Mike
Last edited by Mike Henderson; 06-02-2009 at 10:53 PM.
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