Ch 6 Electrical Checks
A. H
IGH
p
otentIAl
t
eSt
If high potential tests to check the integrity
of the primary insulation is required, the AC
high potential test described below is strongly
recommended. DC high potential testing is not
recommended. The following procedure must
be adhered to:
If DC high potential testing is required, the
DC high potential machine must not produce
peak voltages exceeding 50kV.
CAUTION
Note:
Always recheck with an AC tester if
initial results are questionable.
1) Primary Circuit
The ground and test device should be
hipotted with the ground and test device
closed. An AC hipot machine capable of
producing the test voltages shown below
may be used to hipot the ground and
test device phase to phase and phase to
ground.
The machine should be connected with its
output potential at zero and the voltage
increased at 500 volts per second to the
test voltage and that voltage maintained
for 60 seconds. The voltage should then be
returned to zero and the test leads removed
from the ground and test device and the
ground and test device discharged to
ground.
Note:
Do not exceed the test voltage
indicated for applicable ground and
test device voltage rating. If the test
should experience a failure, STOP,
turn off the test set and discharge the
ground and test device.
1. Check the test set up and leads for
connection errors.
2. Wipe down the ground and test
device to remove any moisture,
dust, and contamination.
3. Retest the ground and test device
at the proper test voltage.
2) Secondary Circuit
Prior to hipotting the ground and test
device secondary circuit, disconnect the
motor leads and thread a wire connecting
all secondary disconnect pins, except #24
the ground pin. Connect the hipot machine
from this wire to ground. Increase the
voltage to 1125V (rms) 60Hz and maintain
for 60 seconds. Reduce the voltage to zero
and remove the hipot machine from the
circuit. Remove the wire connecting the
secondary disconnect pins and reconnect
the motor leads.
3) Primary Circuit Resistance
A resistance check of the primary circuit
may be made with the ground and test
device closed. Use a low resistance
measuring instrument rated 100 amperes
which measures in microhms. The 100
ampere reading should not exceed 100
microhms when connected across the
primary studs on the ground and test
device side of the disconnect fingers. Do
not connect directly to the disconnect
fingers as errors may occur due to finger
spring pressure.
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22
Electrical Checks
Power/Vac® Electrical Ground and Test Devices
Equipped with ML-17 Mechansim
01.4IB.50100
