Re: Yet Another Lo-Budget MOT Experiment

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

Original poster: "Gregory Hunter by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>

Hi Josh,

 > Greg, all-
 >
 > (“Going up to 8kvac with 4 series MOT's solves so
 > many problems and makes things more stable and
 > predictable.”)
 > You mean the MOT’s with the capacitive ballast

I mean a 4-pack, regardless of how it is ballasted. A
static gap is much easier to manage at 8kv than 4kv.

 > correct? I got my hands on
 > this big transformer-
 > Specs: the faceplate on it reads-
 > Ram transformer corp.  #50    type B-29608-Y
 > 5000va     60 cyc     3 ph 6- 73 date
 > Primary- blank  secondary-blank
 > Terminals 1-2-3 430 volts
 > Terminals 4-5-6 460 volts
 > Terminals 6-7-8 200 volts
 > It has 3 windings on an EI core.
 >
 > Sound like a good ballast for a 4 pack?.... at the
 > very least the core
 > laminations will work in my slide choke.)-
 >
 > I was reading that 4 MOT’s and a ballast cause some,
 > um….. “Oddness” in the

Oddness? What sort of oddness? Any big, low-loss,
power transformer (pole xfmer, MOT bank, etc.) used
with an efficient reactive ballast may be subject to
"thumping" or "bucking". I've never experienced it
myself, but I'm aware of the phenomenon. It can cause
lights to dim or brighten, breakers to trip, and
erratic tesla coil performance. I'm no EE, but I'm
guessing 50-60Hz resonance is the culprit. The
"oddness" can be eliminated by adding a bit of ohmic
resistance to the circuit to spoil the Q. I have a
massive 1.6 ohm resistor (weighs several pounds) in my
attic for this very purpose, but I've never needed it.

 > AC phase. This troubles me because I was planning on
 > using a SRSG with my 4
 > pack. I am imprested with your MOT work but I
 > couldn’t find any mention of
 > a sync gap on your site. Have you used one before?

No, I don't own a sync gap.

 > The SRSG I use with my 2, 12/60’s works like a charm
 > (thanks to the folks
 > on the list) and the sparks are slower and longer
 > than my non sync gap
 > work. I like very much how the spark looks and I was
 > going to shoot of a
 > similar performance with my MOT’s. But if the AC
 > phase is shifting all

I don't see why the AC phase would be "shifting all
around". Don't let such a possibility stop you from
using a sync gap.

 > around perhaps an Async gap is best. What do you
 > think?

I don't know if async is "best". I have two async
gaps. I like them because they use a simple, cheap,
unmodified universal motor. I was able to build them
myself without having to visit a machinist. The break
rate can be adjusted with a variac or even a cheap
lamp dimmer.

 >
 > Read you later
 > Josh
 >
 >
Regards,


=====
Gregory R. Hunter

http://hot-streamer-dot-com/greg