Re: Phase shifter update.

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: FutureT@xxxxxxx

In a message dated 4/2/06 1:18:10 PM Eastern 
Daylight Time, tesla@xxxxxxxxxx writes:



> By increasing the cap size to 95.5µF I was
> able to solve the "Motor stops at higher
> inductance setting" problem. Now I get
> a 4V voltage rise, but to the ends of the variac,
> which could possibly be better desribed as a
> voltage drop... but with 99µF I alredy get
> over 10V of voltage rise. My steps in capatitance
> are limited by the caps that I currently have.
> However, there seems to be some phase shifting,
> mybe not too big tough.
> I am not sure if I got that one right: When I add
> inductance, will this cause the phase of the motor
> to lag or to lead in respect to the case, where
> no or less inductance is added by the variac?
> I assumed it was "adding inductance leads to
> later phasing of the gap, but maybe someone
> knows better.


Christoph,

If your motor says synched to the ends of the
variac's range, then all is OK.  The voltage drop
at the end is normal.  If the rotary stays in synch
throughout the variac's range using the 95.5uF,
then you can use that value.  Or you can use the
99uF.

If I understand correctly, you are seeing only one
problem:  Insufficient phase-shift range.  If you're using
an 1800 rpm motor, the maximum mechanical phase
shift is 45 degrees using this phase shifter circuit.
The electrical phase shift is about 90 degrees.  So
if you're getting a 45 degree shift of the rotor.  Then all is well.
You will need to position the rotor on the motor
in a suitable phase position so that the available
phase shift range will give you an optimal phase setting
for your coil at some setting of the variac knob.  In other
words the phase shifter should be used an a fine
adjustment of the phase.  The rough adjustment
should be by the position of the rotor on the motor.

John