RE: SRSG phase adjuster

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

Original poster: "David Dean by way of Terry Fritz <twftesla-at-uswest-dot-net>" <deano-at-corridor-dot-net>

Hi Steve,

> Original poster: "Steve White by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <slwhite-at-zeus.ia-dot-net>
>
> Assuming that I can adjust and lock down my SRSG with the proper
> firing point
> relative to the 60 Hz power line phase, is there any reason to employ the
> variable phase angle circuit for adjusting the motor phase in
> real time? I can
> currently adjust the phase within a few degrees of accuracy and
> then lock down
> the motor in its cradle.
>
I used to do that with my first SRSG. At that time I did not have a variac
to adjust the input voltage, so when I turned it on, it was full blast. It
worked OK, but was a real bear to get to the best firing point. In fact,
with out being able to adjust "on the fly" I have no way of knowing if I
ever actually achieved the absolute best firing point.

At the present time I am using a 5KVA 14.4KV Distribution transformer with a
15/60 NST for ballast. The secondaries are shorted on the NST. It has two
120V primaries which I have wired in series. Putting a milliamp meter across
the output of the pig and ramping up the primary voltage from 0V to 280V
gives almost a linear VI curve with 100mA short circuit current at 280V.

I am using this to power my 4" coil with a 16nF MMC. Using a breakout point,
I get breakout at about 20V out from the variac. I can get about 42" to 48"
strikes and streamers with the variac turned up to about 170V. After that
the safety gap starts to fire. (It is set at 0.75", a bit wide, I know, but
no problems yet.) I am also using the phase shift circuit originated by John
Freau.

When I first get breakout, the phase shift is at minimum, or no shift. A bit
of retard will bring up longer streamers. As I ramp up the variac I adjust
it just a bit and then rephrase the rotary for best sparks. I keep repeating
the procedure until the variac is at the highest voltage the coil will run
at with out the safety firing. At that point, the firing angle has changed
by about 60 degrees.

So it is my opinion that the phase shirt circuit, or at least a variac to
get a little shift by varying the voltage to the motor (that works too) is
well worth the trouble.

later

deano