[Prev][Next][Index][Thread]
MOTs...exploring the low end of TC voltage
Fellow Coilers,
The subject of microwave oven transformers (MOTs) in Tesla coil service
comes up often on this list. In response to the many queries about MOT
power supplies, I conducted a simple experiment. I hooked up two 900 Watt,
2400VAC MOTs in series for 4800vac at around 385ma. I used no ballasting,
no RF filtering, no nothing. Mains current was from a standard 115v 20A
household outlet. I connected the twin MOTs to my 4" x 24" coil which
normally runs on 2 x 9kv/60ma NSTs with .023uF MMC & single static vacuum
gap. I closed the spark gap a bit for reliable firing and let her rip. No
output. I put a breakout point on my toroid and tried again. This time I
got a frantic, brush-like blast of discharge about 12" long! It looked
like a flame! I can't even hazard a guess about how many bangs per second
this thing was going. However, I could only run a few seconds at a time or
the mains circuit breaker would trip. Still, it does demonstrate that a TC
can operate on a low voltage, high current MOT power supply. If my setup
was optimized for such a supply, perhaps by using a bigger tank cap, and if
I ballasted the MOTs or wired them for 230v, I could get useful performance
from what was for me a FREE power supply (my MOTs came from discarded
ovens). In the next few weeks I will wire up the twin MOTs with two
half-wave voltage doublers, proper protective filtering, safety gaps, etc.,
and have a nice 1800 Watt, 12kvdc MOT supply. But now I know the doublers
aren't strictly neccessary. Starving students and other low budget coilers
take heart. Your Tesla coil power supply is only as far away as the
nearest junk yard!
Best Regards,
Greg Hunter
Cochran, Georgia