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M. Inspection and Troubleshooting
1. Inspection and maintenance cycle
■ Precaution
Note) 1. Shall be no withstand voltage test between terminals of circuit breakers for motor
protection.
2. Shall be 1000V of withstand voltage between contacts embedded in Earth Leakage
Relay.
3. This test voltage is based on standards of K60947-4-1 9.3.3.4.3.
The qualified engineer should perform the maintenance and inspection for safety reason and
make sure that main circuit breaker is disconnected from the power supply before placing it
service.
After installing MCCB, make sure the inspection items listed below before supplying
the power.
■ Initial check
Type Inspection item Criteria
Common
1. Shall be no remains after cutting screws, wires around terminal
Shall be no remains
2. Shall be no cracks and breakage on Cover, Case
Shall be no cracks and breakage
3. Shall be no dew condensation on Cover and Case
Shall be no dew condensation
4. Measure the insulating resistance with 500V insulating resistor More than 5㏁
5. Conducting part shall be fully tightened
Specified tightening torque
Main circuit Aux circuit or control circuit
Rated insulating
voltage [UI]
Testing voltage
(A.C effective value)
Rated insulating voltage of
operating circuit
Testing voltage
(A.C effective value)
300<UI≤690 2,500 UI≤60 1,000
690<UI≤800 3,000 60<UI≤600 2Uls+1,000
(1) Withstand voltage test
The standard of withstand voltage test is as follows.
■ Routine Check
1. Clean and dry condition
Once in 2~3years
2. In presence of dust, corrosive gas, vapor, salinity
Once in a year
3. Severer condition than listed above 1,2
Once in a half year
Inspect circuit breaker a month earlier than it is taken into service and a month later to prevent
the accident in advance and to keep circuit breaker in good condition. After that carry out the
inspection according to inspection schedule and then record the result in the routine check
table.
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