Troubleshooting Inverter Problems (Ykmu); Inverter-Related Problems And Solutions - Mitsubishi Electric PURY-HP72 Service Handbook

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[8-11 Troubleshooting Inverter Problems (YKMU) ]

8-11 Troubleshooting Inverter Problems (YKMU)


Inverter-Related Problems and Solutions

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.)
Replace only the fan motor if only the fan motor is found to be defective. (Overcurrent will flow through the inverter if the fan
motor is damaged, however, the power supply is automatically cut when overcurrrent is detected, protecting the inverter from
Replace the defective components if the inverter is found to be defective.
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. Turn off the unit, leave it turned off for at least 10 minutes, and check that the voltage
across FT-P and FT-N terminals on the INV board or the terminals at both ends of the electrolytic capacitor is 20V or below
before checking inside the control box.
(It takes about 10 minutes to discharge electricity after the power supply is turn off.)
2) Disconnect the outdoor unit fan board connector (CNINV) before performing maintenance work. (To plug or unplugconnec-
tors, check that the outdoor unit fan is not rotating and that the voltage of capacitor in the main circuit is 20 VDC or below. The
capacitor may collect a charge and cause an electric shock when the outdoor unit fan rotates in windy conditions. Refer to the
wiring nameplate for details.)
3) To connect wiring to TB7, check that the voltage is 20 VDC or below.
4) Reconnect the connector (CNINV) to the fan board after completion of maintenance work.
5) 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.
6) To avoid damage to the circuit board, do not connect or disconnect the inverter-related connectors with the main power turned
7) Faston terminals have a locking function. Make sure the terminals are securely locked in place after insertion.
8) When the IPM 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.
9) Faulty wiring to the compressor damages the compressor. Connect the wiring in the correct phase sequence.
10) When the power is turned on, the compressor is energized even while it is not operating. Before turning on the power, dis-
connect all power supply wires from the compressor terminal block, and measure the insulation resistance of the compressor.
Check the compressor for a graound fault. If the insulation resistance is 1.0 MΩ or below, connect all power supply wires to
the compressor and turn on the power to the outdoor unit. (The liquid refrigerant in the compressor will evaporate by energiz-
ing the compressor.)
Press the tab on the terminals to remove them.
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