Hi Gene,
The frame is most solidly grounded. I'll do the tests in a bit. Keep in
mind that I have a 240v to 120v step down transformer to supply the 120v
not a normal house circuit. Again an effort to kill the noise. Which by
the way I'm running 2.7 now after changing the wires on the limit/home
switches to twisted pair shielded wire. I've attached the VFD side
wiring diagram. I assume the connection is through the neutral bonding
screw at the panel because the step down transformer is isolated from
ground.
Happy New Year to you too.
JT
On 12/31/2015 5:50 PM, Gene Heskett wrote:
On Thursday 31 December 2015 16:20:40 John Thornton wrote:
On the 120v side if I measure from the hot to the ground I get 79
volts, if I measure from hot to neutral I get the expected 128v...
what is that telling me?
JT
My first guess is that the Bridgeport itself, is not grounded. It really
should be, just to keep it from becoming lethally hot when somethings
insulation fails. Generally speaking, if I can measure more than a volt
between neutral and the static ground, it concerns me UNLESS its a wild
phase , which I don't believe you have since its not a 3 phase circuit.
TBE if something is running that uses that neutral you might see more
volts, but I'd re-measure after turning whatever it was off.
As to the 79 volts, I would put a small light bulb (7.5 watt night lite)
from the Bp frame to neutral to see if there is any real current, or its
just capacitative coupling. If capacitative coupling, a 7.5 watt night
light bulb will remain dark, and that voltage should drop to less than 1
or 2 volts. If it lights up at all, and the voltage doesn't drop
drastically, there really is a fault someplace. I'd start disconnecting
motors for starters.
Happy New Year John.
Cheers, Gene Heskett
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