7-8
7.5
5B
Insulation Test
Since the inverter has undergone an insulation test before shipment, avoid making a Megger test at
the customer's site.
If a Megger test is unavoidable for the main circuit, observe the following instructions; otherwise, the
inverter may be damaged.
A withstand voltage test may also damage the inverter if the test procedure is wrong. When the
withstand voltage test is necessary, contact your Fuji Electric representative.
(1)
Megger test of main circuit
1) Use a 500 VDC Megger and shut off the main power supply without fail during measurement.
2) If the test voltage leaks to the control circuit due to the wiring, disconnect all the wiring from the
control circuit.
3) Connect the main circuit terminals with a common line as shown in Figure 7.2.
4) The Megger test must be limited to across the common line of the main circuit and the ground
(
).
5) Value of 5 M
Ω
or more displayed on the Megger indicates a correct state. (The value is measured
on an inverter alone.)
Figure 7.2 Main Circuit Terminal Connection for Megger Test
(2) Insulation
test of control circuit
Do not make a Megger test or withstand voltage test for the control circuit. Use a high resistance
range tester for the control circuit.
1) Disconnect all the external wiring from the control circuit terminals.
2) Perform a continuity test to the ground. One M
Ω
or a larger measurement indicates a correct
state.
(3) Insulation
test of external main circuit and sequence control circuit
Disconnect all the wiring connected to the inverter so that the test voltage is not applied to the
inverter.
