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Re: First Light at Last! (update)
Mark,
Not clear just why it chose to break down at the thermostat, but that
apparently was the "weakest link" at the time. However, the point still
remains that you're picking up enough voltage to cause breakdown in this
circuit, either through magnetic induction from the close proximity of
the TC primary winding, or from the near field of the TC in the wires
going between the motor and the variac in your control box. BTW,
near-field pickup can ALSO couple into your house wiring if you happen
to use house wiring in the area near the coil that's not contained
within metallic conduit, or if you have nearby large sections of
conductive metal (such as aluminum siding) that are not grounded. Some
coilers on this list have actually started small fires due to induced
voltage and arcing... :^)
To fix your motor problem, you may want to add a couple of 600 volt (or
better) bypass capacitors between each motor lead and the case of the
motor to bypass induced RF around the windings, and use a similar
approach on the controller end. Other coilers have successfully used EMI
line filters (internally, a combination of coupled inductors and bypass
caps) to do the same thing. Also, try wiring the motor with a pair of
wires close together (like regular 120V. zip-cord), and also try to
route these wires so that they are short, and at a right angle to the
primary wiring - this should reduce the magnitude of direct inductive
coupling from the primary. Finally, if you still have problems, you may
need to physically increase the vertical distance between the motor and
the TC primary above.
Safe coilin' to you, Mark!
--
Bert Hickman
Stoneridge Engineering
http://www.teslamania-dot-com
Tesla List wrote:
>
> Original Poster: "Mark Broker" <broker-at-uwplatt.edu>
>
> Gary, Bert, and others,
>
> Just as a clarification, and another question.
>
> I have a safety gap across my RSG (re-designed: see "NST saturation post").
> The
> RSG was set to "just about right" when it happened. The motor is at least 4"
> from any NST terminal, and there is no way possible that the arc from
the gap
> jumped to the motor (I *REALLY* wish that I had a web page so that you
> could see
> it).
>
> I am running the motor on a variac (not the NST variac), which I only use to
> start the motor. I set it to 120 after the motor spins up. My "control
panel"
> is set up such that the NST and motor can be run from totally seperate
"house"
> circuits, since I was thinking that I'd end up drawing about 22A total....
>
> If the motor failed at it's weakest link, then why didn't a insulation on the
> turns fry? Or, why didn't it arc across the connection terminals, which are
> only about .5" apart in air? (The arc from the thermostat was about .25"
> through some tough, thermoset plastic.) I certainly hope that I don't
further
> mess the motor up when I add another NST (with a corresponding increase
in the
> LTR cap).
>
> Thanks!
>
> Mark
<SNIP>