Maintenance and Inspection
8-5
The details of periodic inspections are described below.
Megger Check (Measurement of Insulation Resistance)
1. Measure insulation resistance of the Inverter primary circuit.
Use a 1000 V Megger insulation resistance tester. The measured insulation resistance must be 2 MΩ or
more.
As the primary circuit is grounded at high-resistance for input voltage detection, isolate both the grounding
line and the detection signal lines that are connected to the control board before measuring insulation resis-
tance.
2. Measure insulation resistance of the Inverter secondary circuit (motor side)
Use a 1000 V Megger insulation tester. The measured insulation resistance must be 2 MΩ or more.
As the secondary circuit is grounded at high-resistance for output voltage detection and ground-fault detec-
tion, isolate the high-resistance resistor and Power Cell output cables connected to the output terminals
before measuring insulation resistance.
(If a secondary switchgear is provided, it is convenient to open the contactor and measure the insulation
resistance at the secondary switchgear output terminals.)
Screws, Bolts, and Connectors
Loose I/O terminal bolts and/or loose board connectors can cause failure or malfunction of the Inverter. Dur-
ing periodic inspection, be sure to retighten the screws and bolts and re-insert the connector securely.
Inspect the following terminals and connectors.
• Medium-voltage I/O terminals
• Input and output voltage detection circuits (high-resistance section)
• Transformer I/O terminals and primary voltage tap terminals
• Transformer output terminal block
• Power cell I/O terminals and optical fiber cable connector
• Power cell screws, bolts, and connectors
• Control power supply input terminals
• Control transformer I/O terminals
• Cooling fan contactor I/O terminals
• Control fuse I/O terminals
• Screws, bolts, and connectors of each control board
• External I/O terminals
Tighten the M10 bolts of medium-voltage I/O terminals with a tightening torque of 1800 to 2300 N•cm.
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