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Re: calculating bps for sync rsg



> Original Poster: "Jon Lagler" <rockcrawl-at-netzero-dot-net>

Hi Jon,

The formula for BPS:     BPS =  (breaks * RPM) / 60
The number 60 just cuts the value from minutes down to seconds.
The frequency of the motor (50Hz or 60Hz) has been taken into account in
the RPM
value.
breaks = rotating electrodes x stationary gaps (usually 1).

For example, if you have "two" stationary gaps series connected and your
rotating
electrodes cross both gaps at the same time, then it is still only one
stationary
gap (mathematically) the rotating electrodes pass through. However, if the two
stationary gaps are offset, then you would use 2 x rotating electrodes for the
break value. Some coilers use 2 or more stationary gaps hooked in series to
help
the spark at the gap quench (stop conducting).

If your motor has 4 rotating electrodes and 1 stationary gap, then

BPS = (breaks * RPM) / 60 = ((4 * 1) * 1750) / 60  = 7000 / 60 = almost 117 BPS

BTW, a 1/2 HP motor is a decent size to use for a gap. Your gap speed should
remain relatively steady under spark gap loading conditions. Sometimes, we turn
our 1750's into 1800 RPM (60Hz) synchronus motors (SRSG) so it will lock
onto the
line voltage frequency. This is done on a 1750 RPM motor by grindnig 4 flats of
equal size and spacing on the armature. There are many posts in the list
archives
at www.pupman-dot-com regarding just how this is done. One of the tradeoffs
with doing
this is loosing torque - after this is done on a motor, it has less umph..
to keep
it's speed under loading conditions. This is another reason why it nice to
have a
1/2 HP motor or larger for this type of work. If the loading isn't too
much, then
even small 1/3 or so HP motors will work of course. It's a load dependent
thing.
I'm using a 1/3 HP motor and haven't had problems on my pig powered system,
but I
would feel better with a 1/2 HP or bigger motor. I can get right to edge of
loading it down which will take it out of sync. So far, current limits have
kept
the spark loading down so it does ok, but when I upgrade breakers (and I
will), I
may run into sync trouble. Also, one last tid bit - a direct drive (rotary disc
attached directly to the shaft) is less likely to load down a motor than drives
that use belts, etc.. It's a friction loading thing. Done them both. Direct
drive
is the best method for most applications, unless your driving a huge gap system
for a 20 foot coil, then direct drive disc size becomes rediculous.

Hope this helps more than confuses,

Bart


>
> Hello,
>  This may be a dumb question, but please bear with me, I'm kinda new at this.
> How do I calculate the break rate of my synchronous rotary gap? My rotor
has 4
> contacts. it is a 1/2 hp motor, 1725 rpm(I think), 60hz. Whatever it is, it
> seems to work well.
>
>
> Thanks in advance,
>  Jon