Re: phase shifter with run-cap sync motors

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

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

In a message dated 2/17/01 10:14:32 PM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

> Original poster: "Metlicka Marc by way of Terry Fritz 
<twftesla-at-uswest-dot-net>" <
> mystuffs-at-orwell-dot-net>
>  
>  john, all
>  in my testing of my 1/3 hp sync. motor i found that with the run cap of
>  12.5uf i
>  could not go over 20uf of phase shift capacitance or the spikes in the
>  waveforms
>  started to cause some sierious "bucking".
>  i tried different values up to 80uf where the motor simply wanted to jump
>  out of
>  it's cradel.
>  20uf seemed best for this motor giving a full 180degrees of electrical
>  shift from
>  the incoming waveform without to much resonant rise, the motor locked up at
>  65v 

Marc, all,

This motor behaviour is very similar to what Alan Jones has found,
and is valuable info for those who are setting up their phase shifter
circuits.  I must say though, that I'm not convinced that you are seeing
180 degrees of electrical shift (we spoke of this before).  I believe that 
this circuit cannot shift the phase more than 90 degrees electrical.
I would wish that you are right about the 180 degrees, because it
would make the phase shift system even better   :)   Certainly with
a more complex circuit using separate stages, more than 90 degrees
could be obtained however.  

I'll be looking forward to your further findings.

I have not heard of anyone else seeing more than a 90 degree phase
shift.  If anyone has, please let me know.

Thanks,
John Freau