25
Instruction Book
IB182023EN March 2016 www.eaton.com
AMH-4.76-VR
Replacement Circuit Breaker
6.5 INSULATION
In VR-Series breakers, insulation maintenance primarily consists of
keeping all insulating surfaces clean. This can be done by wiping off
all insulating surfaces with a dry lint free cloth or dry paper towel.
In case there is any tightly adhering dirt that will not come off by
wiping, it can be removed with a mild solvent or distilled water.
But be sure that the surfaces are dry before placing the breaker in
service. If a solvent is required to cut dirt, use Isopropyl Alcohol or
commercial equivalent. Secondary control wiring requires inspection
for tightness of all connections and damage to insulation.
6.6 INSULATION INTEGRITY CHECK
PRIMARY CIRCUIT:
The integrity of primary insulation may be checked by the AC high
potential test. The test voltage depends upon the maximum rated
voltage of the breaker. For the breakers rated 4.76 kV, 8.25 kV and
15 kV the test voltages are 15 kV, 27 kV and 27 kV RMS, 60 Hz
respectively. Conduct the test as follows:
Close the breaker. Connect the high potential lead of the test
machine to one of the poles of the breaker. Connect the remaining
poles and breaker frame to ground. Start the machine with output
potential at zero and increase to the test voltage. Maintain the test
voltage for one minute. Repeat for the remaining poles. Successful
withstand indicates satisfactory insulation strength of the primary
circuit.
Open the breaker. Connect the high potential lead of the test
machine to one of the poles of the breaker. Connect the remaining
poles and breaker frame to ground. Start the machine with output
potential at zero and increase to the test voltage. Maintain the test
voltage for one minute. Repeat for the remaining poles. Successful
withstand indicates satisfactory insulation strength of the primary
circuit.
If a DC high potential machine is used, make certain that the peak
voltage does not exceed the peak of the corresponding AC RMS test
voltage.
SECONDARY CIRCUIT:
Isolate the motor by disconnecting the two motor leads from the
terminal block. Connect all points of the secondary disconnect pins
with a shooting wire. Connect this wire to the high potential lead
of the test machine. Ground the breaker frame. Starting with zero,
increase the voltage to 1125 RMS, 60 Hz. Maintain the voltage for
one minute. Successful withstand indicates satisfactory insulation
strength of the secondary control circuit. Remove the shooting wire
and reconnect the motor leads.
Figurt 6.3. Tht Arrow Shows Tht “T” Contact Wipt Indicator -
Examplt with Blut Spring (If tht “T” or any portion of its visiblt
as shown with tht brtaktr clostd, tht wipt is satisfactory)
(Stt Ntxt Figurt for Graphic of All Possibilitits)
Whitt Contact Springs
Any part of Red or Gray Indicator Visible
“Wipe” Satisfactory
Red or Gray Indicator Not Visible
“Wipe” Unsatisfactory
Any part of “T” Shape Indicator Visible
“Wipe” Satisfactory
“T” Shape Indicator Not Visible
“Wipe” Unsatisfactory
Blut or Rtd Contact Springs
Figurt 6.4. Wipt Indication Proctdurt
(Ptrformtd Only With Brtaktr Clostd)
