30
Instruction Book
IB182012EN March 2017 www.eaton.com
50DH-VR-50AXU / 50XU / 75U / 75ARU - 600 / 1200A
Replacement Circuit Breaker
6.6 INSULATION
In VR-Series circuit 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. Be sure that the surfaces are dry before placing the
circuit 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.
6.7 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 circuit breaker.
Conduct the test as follows:
Close the circuit breaker. Connect the high potential lead of the
Figure 6.2. Contact Wipe Inspection Area
Figure 6.3. Satisfactory Contact Wipe Condition with Circuit
Breaker Closed
Figure 6.4. Unsatisfactory Contact Wipe Condition with Circuit
Breaker Closed
Drive
Insulator
Top
Inspection
Area
Top Surface
Drive Insulator
Wipe Indicator
Below Top Surface
Top Surface
Drive Insulator
Wipe Indicator
Flush with Top
Surface
Circuit Breaker Rated
Maximum Voltage
Test Voltage
5 kV
15 kV
test machine to one of the poles of the circuit breaker. Connect
the remaining poles and circuit 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.
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 circuit breaker frame. Starting
with zero, increase the voltage to 1500 volts RMS. 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.
