Megger Test - Hitachi SJ300 Series Instruction Manual

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, PD, P, N, RB, U, V, and W]. Most importantly, the
4. Remove the jumper at connector J61. It is located on the main circuit board beside the
5. Use a bare wire and short terminals [R, S, T, PD, P, N, RB, U, V, and W] together as shown
6. Connect the megger to the inverter Earth GND and to the shorted power terminals as shown.
7. After completing the test, disconnect the megger from the inverter.
8. Reconnect the jumper at connector J61 as before.
9. Reconnect the original wires to terminals [R, S, T, PD, P, N, RB, 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.
input power and motor wires will be disconnected from the inverter.
power terminals.
in the diagram.
Then perform the megger test at 500 VDC and verify 5MΩ or greater resistance.
Disconnect
power source
L1 R
L2 S
L3 T
J61
Disconnect jumper at
J61 before performing
the megger test
SJ300
U
V
W
P
PD
RB
N
Earth
GND
SJ300 Inverter
Add test
jumper wire
Disconnect
motor wires
Motor
Megger, 500VDC
6–11