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Posted by TWayne on August 25, 2008, 12:10 pm
> TWayne wrote:
>
> ...
>>
>> A 40" fan has to have a pretty good sized motor and takes several
>> seconds for it to come up to speed. Everything being reactive,
>> while it is starting, it is creating reverse EMF
>> (electro-motive-force) which, during that time, is making the
>> current in the two feed wires go out of phase with each other.
> B.S. Unless you have a very big reservoir for electrons, the current
> on the two feed wires will not be "out of phase".
> A large capacitor to ground would be such a reservoir, but that is
> a ground fault, and the GFCI should trip for that.
>
> ...
>> If it still pops, you could try VERY CAREFULLY (ELECTRICITY CAN
>> *KILL* YOU) TRY shorting around the GFCI with a lead until the fan
>> gets running. Then remove the bypass; If the fan continues to run,
>> there is there is no problem with the fan.
> Not necessarily. There may be both mechanical and electrical
> differences in the motor during acceleration that could cause
> a ground fault during acceleration. OP didn't mention whether
> this motor had a centrifugal switch controlling the start winding.
>
> Most likely you have a ground fault in the motor.
> It may be solid or it may be intermittent.
> Have you tried measuring the resistance from hot to ground
> for the motor?
Since Neutral and Ground are tied together back in the breaker box,
that's not going to prove anything without disconnecting the wires and
even then without a voltage to break down the gap it likely wouldn't
show anything but the resistance part of the fan motor.
I wouldn't even bother with that; it'll measure near zero, only a few
ohms to a hundred or so depending on the fan motor coils.
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