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Re: SRSG v. DC-RSG

Original poster: Esondrmn@xxxxxxx 

Dan,

I had a commercial cap explode when using a 5 kva 14.4 kv transformer with an arc welder in series with the primary for ballast. This was with an async rotary gap. The arc welder was causing a 60 hz resonance with the transformer and the resultant voltage in the Tesla coil primary was extremely high, much higher than I had designed for. I put a static safety gap across the caps set to about .625" and it would fire like a rifle. I then moved it to be in parallel with the async rotary gap so it would not damage the surviving caps. Then I devised another means of ballast and solved the problem. I still have this safety gap mounted across the new sychronous rotary gap. As you would expect, it never fires now, set to about .50". I strongly recommend using a safety gap across your rotary. Once you get everything well dialed in and plan no more modifications, you could certainly remove it. It is much cheaper than buying new caps.

Ed Sonderman

In a message dated 12/2/04 5:59:53 PM Pacific Standard Time, tesla@xxxxxxxxxx writes:

Original poster: "Daniel A. Kline" <daniel_kline@xxxxxxxxxxx>

Hi All,
For the first time in several years, I'm about to add a rotary spark-gap
to a system. The last time I used a rotary spark-gap, it was
asynchronous, and didn't work well with the setup I had.

This time I'm using a 1.5KVA potential xformer at 14.4kV, and I'll be
testing Maxwell caps and MMC configurations to see which is best for
this particular coil.

I'm wondering if I should try a variable break-rate rotary-gap on a DC
motor, or if I should try a synchronous rotary-gap.

The reason I ask is because I had a cap explode when using an
asynchronous rotary-gap, and I'm concerned that the same thing might
happen if, while testing,  I'm continuously varying the break-rate using
the DC-motor rotary-gap.

I have DC motor handy, and I don't have a sync motor yet, but I've been
wanting an angle-grinder for a while now, so it wouldn't take much
convincing for me to go out and get one for machining the appropriate
AC-motor armature ;)

Also, does anyone know of a decent tachometer circuit I can use in
conjunction with the DC-motor in case I go that route?

Thanks,
Dan K.