Testing - John Freau's SRSG Phase Controller

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Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi All,

Tonight I hooked up the stuff and ran John's controller with both of my
rotary gaps.  It works great!!  I could easily get 3mS (~70 degrees) of
variation in the phase.  

As I suspected, the computer model was not real accurate but the basic
principles it showed were real.  I felt a lot better hooking things up
knowing what the computer suggested would happen.  The resistor I suggested
earlier is not needed.  The motor is doing it's job for us so you can
forget that.  The fuse on the capacitor is a winner as John explained in
his test tonight.  If something goes bad (open load), it will keep the
thing from doing a Chernobyl.  There is a very real and nasty 60Hz LC
resonance between the variac inductance, the cap, and the AC line right as
you take the variac up it's range.  The variac saturates into a full power
square wave preventing a major explosion, but the fuse has to act pretty
fast to save the day.  The higher the voltage rating on the cap the better.
 You should not run this open load or with anything but the motor
connected.  Other loads my do bad things...

There is an auto transformer affect which tends to drive the variac's open
end terminal to high voltage (~200 volts AC) at the beginning of the range.
 The high current across a small portion of the variac's winding causes
this high voltage at the other end.  Saturation and carful capacitor
selection controls this.

The variac is probably not very critical but the capacitor's value is.  Too
low and the range is limited, too large and the currents and auto
transformer effects get bad.  I found that 110-130 is the range with 120uF
being the value you really want for a 60Hz, 1800RPM, 1/4HP sync motor.

I did not see anything alarming except the conditions I mentioned above.
The thing seems very stable and nothing is getting overloaded.  It looks
like a real winner!!  The sharp current spikes of the motor do tend to
cause humming in the variac at certain settings but nothing bad is
happening.  I drew up the circuit I used at:

http://hot-streamer-dot-com/TeslaCoils/Misc/SRSG14HP.gif

Other motors will need the cap value adjusted but this should work for
60Hz, 1800RPM, 1/4HP sync motors.  Of course, all this is pretty new so
there may be hidden things we still don't know about.  However, it looks
great to me.

Great idea John!  Your circuit will be around Tesla coiling for a very long
time!!

Cheers,

	Terry