6–10

Maintenance and Inspection

Troubleshooting and Maintenance

Megger Test

The megger is a piece of test equipment that uses a high voltage to determine if an insulation degradation has occurred. For inverters, it is important that the power terminals be isolated from the Earth GND terminal via the proper amount of insulation.

The circuit diagram below shows the inverter wiring for performing the megger test. Just follow the steps to perform the test:

1.Remove power from the inverter and wait at least 5 minutes before proceeding.

2.Open the front housing panel to access the power wiring.

3.Remove all wires to terminals [R, S, T, RB, PD/+1, PD/+, N/–, U, V, and W]. Most importantly, the input power and motor wires will be disconnected from the inverter.

4.Use a bare wire and short terminals [R, S, T, RB, PD/+1, PD/+, N/–, U, V, and W] together as shown in the diagram.

5.Connect the megger to the inverter Earth GND and to the shorted power terminals as shown. Then perform the megger test at 500 VDC and verify 5MΩ or greater resis-

tance.

 

 

 

 

 

 

 

 

 

 

 

 

Add test jumper wire

Disconnect

 

 

 

 

 

 

 

 

 

Disconnect

power source

 

SJ200

 

motor wires

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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RB

 

 

 

Megger, 500VDC

 

 

 

 

 

 

 

 

 

 

PD/+1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PD/+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

N/–

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Earth GND

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6.After completing the test, disconnect the megger from the inverter.

7.Reconnect the original wires to terminals [R, S, T, RB, PD/+1, PD/+, N/–, U, V, and W].

CAUTION: Do not connect the megger to any control circuit terminals such as intelligent I/O, analog terminals, etc. Doing so could cause damage to the inverter.

CAUTION: Never test the withstand voltage (HIPOT) on the inverter. The inverter has a surge protector between the main circuit terminals above and the chassis ground.