Original poster: "Breneman, Chris" <brenemanc@xxxxxxxxxxxxxx>
Hello,
I've almost finished the MOT power supply for my first Tesla coil,
but have a few questions about its operation. The supply consists of
two MOTs with the primaries in parallel and secondaries in series and
a third MOT in series with the parallel arrangement of the first two
acting as a ballast. The ballast has its high voltage winding
shorted. All of them run on 120V. In addition to the transformers,
I also have a 15A circuit breaker in series with the circuit, and the
house has its own 15A breaker on this circuit.
I recently received a 15A analog panel ammeter which I wanted to use
in the circuit to monitor current drawn. It is placed in series
between the breaker and the ballast. When I run the power supply
with the hv end shorted, no breakers trip, but the ammeter reads off
the scale. When I replaced the analog meter with a digital
multimeter capable of reading up to 20A, it read "Overload". What I
don't know if if more than 15A is really flowing, and if it is, why
it isn't tripping the breakers, and if it isn't, why do the meters
show that it is?
The only possible cause I can think of for this discrepancy is that
the power factor is probably greatly offset by the highly inductive
load, but why wouldn't the breakers trip in this case? I also tried
the circuit with a 10uF PFC capacitor, and saw no difference in
behavior. If the problem is the power factor, do you think a 180uF
PFC capacitor would be reasonable for such a supply? The open
circuit voltage is slightly over 5kV and the short circuit current is
slightly over 500mA (that is, assuming these readings from the
digital multimeter are correct; I determined these values indirectly
by measuring current through different resistances on the hv side).
Thanks a lot,
Chris