Mitsubishi Electric PQHY-P120THMU-A, Service Handbook

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[
IX
Troubleshooting ]
- 328 - HWE09080 GB
-6- Inverter (THMU-A)
Œ
Replace only the compressor if only the compressor is found to be defective. (Overcurrent will flow through the inverter if the
compressor is damaged, however, the power supply is automatically cut when overcurrent is detected, protecting the inverter
from damage.)
Œ
Replace the defective components if the inverter is found to be defective.
Œ
If both the compressor and the inverter are found to be defective, replace the defective component(s) of both devices.
(1) Inverter-related problems: Troubleshooting and remedies
1) The INV board has a large-capacity electrolytic capacitor, in which residual voltage remains even after the main power is
turned off, posing a risk of electric shock. Before inspecting the inverter-related items, turn off the main power, wait for 5 to 10
minutes, and confirm that the voltage at both ends of the electrolytic capacitor has dropped to a sufficiently low level.
2) The IPM on the inverter becomes damaged if there are loose screws are connectors. If a problem occurs after replacing some
of the parts, mixed up wiring is often the cause of the problem. Check for proper connection of the wiring, screws, connectors,
and Faston terminals.
3) To avoid damage to the circuit board, do not connect or disconnect the inverter-related connectors with the main power turned
on.
4) Faston terminals have a locking function. Make sure the terminals are securely locked in place after insertion.
5) When the IPM, diode stack, or IGBT is replaced, apply a thin layer of heat radiation grease that is supplied evenly to these
parts. Wipe off any grease that may get on the wiring terminal to avoid terminal contact failure.
6) Faulty wiring to the compressor damages the compressor. Connect the wiring in the correct phase sequence.
Press the tab on the terminals to remove them.
[THMU-A]