Mitsubishi Electric PURY-P72 Service Handbook page 330

[ IX Troubleshooting ]
[YKMU-A]
Inverter (YKMU-A)
-7- Inverter (YKMU-A)
ŒReplace 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.)
ŒReplace 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
damage.)
ŒReplace the defective components if the inverter is found to be defective.
ŒIf 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) Perform the service after disconnecting the fan board connector (CNINV) and the inverter board connector (CN1 or CN-
FAN).(To plug or unplugconnectors, 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) back to the fan board and reconnect the connector (CN1 or CNFAN) back to the inverter
board after servicing.
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
on.
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 M 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.)
HWE1116D
Press the tab on the terminals to remove them.
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