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Re: synchronous motors

Original poster: William Beaty <billb@xxxxxxxxxx>

On Tue, 9 Aug 2005, Tesla list wrote:

> Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
>
> Your right Bill. When I built my SRSG, I used a rotating stationary
> setup. It easily honed in on the big sparks. As you said, it's
> obvious when you get it right (I use to just play with it to see the
> difference - and it's a major difference).

To get rid of the low parts of the power line wave, mine had a fullwave
bridge on the HV supply, plus a bit of filtering.  Lots of microwave oven
diodes.

But the syncro motor phase still made an easily seen difference
in spark length, even though the changes in rotary gap phase were only
tracing out the remaining ripple.  That darned stored energy is
proportional to volts squared, so a small improvement in drive voltage
doesn't just give a proportional increase in power, instead it gives twice
as much increase.  Because of V^2, the effect of any ripple is doubled.

And the ripple of unfiltered AC on a rotary gap system is enormous, that's
why I tried to use DC before later trying a syncro motor.  With smooth DC
the rotary gap speed becomes irrelevant, but for impressive results it'd
be much better to use pure AC with a properly phased syncro motor.
Essentially you're cranking the HV supply voltage higher.  The rotary gap
acts something like a mechanical rectifier; only delivering the top AC
peaks to the primary circuit.

> These days, I'm not even using an SRSG. I've moved back to a variable
> speed gap with VFD controlled 3-phase motor. I just like that speed
> adjust at my finger tips. That "varoom" sound is simply too cool! ;-)

Ooooo!   Has anyone made a dual coil with TWO SEPARATE rotary gaps with
variable motor speed?   Create two independant "varoom" sounds.  Scare the
neighbors with noises like a UFO invasion.



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William J. Beaty                            SCIENCE HOBBYIST website
billb at amasci com                         http://amasci.com
EE/programmer/sci-exhibits   amateur science, hobby projects, sci fair
Seattle, WA  206-789-0775    unusual phenomena, tesla coils, weird sci