Re: RSG adjustment

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Esondrmn-at-aol-dot-com>

In a message dated 3/24/02 11:21:00 AM Pacific Standard Time, tesla-at-pupman-dot-com
writes:


>
> Various motors of the same HP motor ratings will require vastly
> different capacitance values.  But 250uF does sound high for a
> 1/2HP motor Steve, unless you've tested it already, and found 
> the correct resonant rise and performance with that value.  I seem
> to remember someone saying they needed to use 120 or 180uF
> for their particular 1/2HP motor.  The motor rpm (1800 or 3600rpm),
> also seems to affect the capacitor value requirements.  Generally
> smaller cap values will probably cause less self breaking problems,
> even with larger motors, but I'm not sure.  All the motors I've used
> were 1/4HP or less.  I should really add more info at my website
> about the various cap sizes and ranges needed for various motors.
> So far I've used the phase shifter on five different SRSG's of
> various HP ratings.  I suspect that the needed cap value may
> also depend on how heavily the motor is loaded by the rotor.
> I'm not sure about that either though.  The needed cap value
> may depend more on the motor load than the motor rating?
> The current drawn by the motor may give some clue to the
> needed capacitance.
>
> Cheers,
> John




John,

I am using a 1/3 H.P. GE 3600 rpm synchronous motor.  Using your phase control
circuit and a 10 amp Powerstat variac as a variable inductor (0 to 258 mh), I
needed 254 mfd of capacitance in order to get full adjustment on the phase
control variac.  I get 5 volts of resonant voltage rise at about 50% on the
variac setting.  I am not sure exactly how many degrees of phase control I am
getting but  I can adjust to either 120 bps or 240 bps.  This is using 4
contacts on the rotor so at 120 bps 2 contacts are firing at 90 degrees and 270
degrees, the other two are at zero crossing.  Then shifting 45 degrees has all
four contacts firing (at 45 degrees and 135 degrees after each zero crossing).

Ed Sonderman