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Re: Input/Output Power
---------- Forwarded message ----------
Date: Sat, 4 Oct 1997 13:21:13 -0700
From: Jim Lux <jimlux-at-earthlink-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Input/Output Power
> The fluke measured 165mv! This equates to over 60 amps at 250VAC. I
only
> have 30 amp breakers on this line. Is the reading wrong, or is the
breaker
> too slow, or not good for this application????
Here are some possibilities for the anomalous current readings:
1) Your DVM probably measures peak voltage then divides by 1.4 to read in
RMS AC volts. This is only true for sinusoidal waveforms, if your current
waveform is pulsed, the RMS current could be quite low, even though the
peak current is high. The circuit breaker is probably thermal, so it
measures true RMS current.
2) The current may be high, but out of phase with the voltage, so the
ACTUAL POWER drawn is low, even though the APPARENT power is high. That is,
you have a terrible power factor, which, if you were an industrial plant
would result in a visit from the electric company to find out why. This is
unlikely, because the circuit breaker measures (in some way or another) the
current magnitude. However, if there is some component between your
measurement point and the circuit breaker that can provide power factor
compensation, you could get the results you see. Your load (i.e. the tesla
coil system) is probably pretty inductive (even without an inductive
ballast), so a capacitor on the other side of the meter would fix the power
factor seen by the circuit breaker, but the var flow back and forth between
the inductor and capacitor would result in a higher current reading.