[TCML] Questions on the Freau SRSG Phase Controller
deano at deanostoybox.com
Fri Sep 24 07:35:31 MDT 2010
I made a SRSG several years ago around the time John first described his phase controller to the
list. I used a 1/3 HP 3450 RPM A.O. Smith motor which was very easy to take apart and put together.
At the time there was only the "dead pole" method for determining the width of the flats. The motor
had no dead poles, so I just milled a little bit, checked sync, milled a little more, etc. until I
was able to get it to lock at down to 90V input. My theory was that the motor should pull 80%
nameplate FLA when locked and spinning the RSG disk. I was getting no where near that amp draw, so I
checked the wiring and low and behold the thing was set to 230V but had been running for years as a
bench mounted wire wheel on 120V. I had assumed it was set for 120V.
Long story short I was able to get approx 75 degrees of phase shift just by changing the input
voltage over the range 90 to 230 Volts. Changing to Johns phase controller circuit gave me almost
the full 90 degrees, and if I remember correctly (been a few years since it has run, capacitors all
given away in the mean time) I was using 55uF. I never checked for voltage rise, and never reached
80% FLA either.
The required capacitance for any given installation will depend on the particular variac used as
well as the motor itself, and (I think) how much material was removed when making the "flats".
In my case I used a Staco type 2pf 1010 120V input 0-140V output 10A variable autotransformer for
the phase controller (230V input to the circuit). I do not know the ratio of the width of the flats
to the diameter of the rotor. I suspect my flats are a bit wider than that recommended today.
Hope this helps
> The line-power LED I described works reasonably well. I have tried
> capacitances up to 155uF so far, and am unable to exceed about 45 degrees
> before losing lock. I never see a resonant rise in the voltage across the
> motor. Has anyone used 1/2 HP motor, 3600 RPM with John's phase
> controller? What capacitance did you find to be ideal?
More information about the Tesla