Re: 5HP rotory elect. phase control

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Steve White by way of Terry Fritz <twftesla-at-qwest-dot-net>" <slwhite-at-zeus.ia-dot-net>

Does anyone know of an adequate model for a motor while running? An
inductor? I have been looking at John Freau's phase shifter circuit and it
appears to be a bandpass filter with a center frequency of 60 Hz feeding the
motor. If I could model the motor, I could analyze the filter
characteristics. I presume that as the inductor (variac) is varied, the
center frequency of this bandpass filter changes slightly. This would
explain why you want to see a resonant rise. The presence of the resonant
rise would indicate that you have implemented a 60 Hz center frequency
bandpass filter. Since analog filters have a non-linear phase
characteristic, this would also explain why the phase shifting action takes
place. As you change the inductance, you slighlty change the center
frequency of the filter and also changes the phase angle of the voltage. If
I could model the motor, I think that I could analyze the filter
characteristics and quantify the component values. I am attempting to remove
most of the guess-work from selecting the capacitance value for a particular
motor.

Steve: Coiling in Iowa

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, March 27, 2002 11:31 AM
Subject: Re: 5HP rotory elect. phase control


> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<FutureT-at-aol-dot-com>
>
> In a message dated 3/27/02 1:16:06 AM Eastern Standard Time,
tesla-at-pupman-dot-com
> writes:
>
>
> >
> > so this encouraged me to finish my 5HP 3600 RPM rotory project.
> > I was a little worried about being able to make John Freau's phase
> > control work on such a large motor, but it does work after all.  The
> > optimal capacitance is around 85 uF using a 10 amp 120 volt variac for
> > control.
>
>
>
> Hi Kevin,
>
> Nice !   I think the 240 volt operation lets the cap value be much
> smaller than otherwise.  Perhaps 1/2 or 1/4 the size that it would
> need to be for 5HP at 120 volts.  Your results also strengthen my
> suspicion that the cap value requirements depend somewhat on
> the motor load, not only on the motor HP rating.
>
> Cheers,
> John
>
>
>