M Q wrote:
bud-- wrote:
...
Assume capacitance is equal from both hot and neutral to pole. Leakage
also depends on voltage. The neutral end is connected to pole (at the
service panel). The voltage from N-to-pole will be minimal. I suspect
the winding is constructed so the neutral end is most toward the pole
but don't know. Could try reversing the motor H-N leads.
Capacitor across H-N - maybe. The capacitor does not dissipate the
energy but may spread it over time and lower the peak voltage. MOV
might work but I wouldn't connect one L-N without protection. My guess
is a shunt resistance would probably have to be too low value so that
it dissipates significant energy.
I wouldn't guarantee trip is from capacitance-spike but it is the best
guess I can come up with.
Another possibility: I have often seen the armature of motors, when
they
turn on or off, shift axially. If so, there could be a transient short.
If a supply wire was near an end of the armature - could be.
Note that GFCIs detect a fault from neutral to ground also. From the
schematics I have seen, I believe they do this by inducing a higher
frequency
common voltage on the the hot and neutral. If there is neutral
to ground fault there will be a common mode current of this higher
frequency signal which will be detected by the same circuitry and trip.
The point is: don't ignore a ground fault on the neutral side.
What I remembered was inducing a current into just the neutral. A
manufacturer's datasheet shows common mode induction into both H & N
like you said. That would also give "neutral"-ground fault detection if
the hot and neutral wires were reversed. The data sheet shows a fullwave
rectified 60Hz source, which would be 120Hz with harmonics.
When there is load on a circuit with a GFCI, resistance will cause a
voltage from neutral to ground, and there will be current in a N-G fault
that will trip the GFCI. With the added circuitry a GFCI will trip on a
N-G fault with no load.
(datasheet is at
http://cache.national.com/ds/LM/LM1851.pdf
--
bud--