Mitsubishi Electric CITY MULTI PUHY-400YMF-C Service Handbook page 147

6) Troubleshooting at breaker tripping
Check items
1 Check the breaker capacity.
2
Check for a short circuit or grounding in the electrical
system other than the inverter.
3 Check the resistance between terminals on the terminal
block TB1A for power source.
1
0 ~ several ohms or improper megohm value
4 Checking by powering again.
1
Main power source circuit breaker tripping
2
No display of remote controller
5 Operational check by operating air conditioner
1 Normal operation without breaker tripping.
2 Breaker tripping
Measures to be taken
The breaker's capacity should be correct to "System
design" in data book.
Correct any defects.
Check each part inside the inverter power circuit
(resistance, megohm or the like).
a) Diode stack
Refer to "Troubleshooting of diode stack."
b) IPM
Refer to "Troubleshooting of IPM."
c) Rush current protection resistor
d) Electromagnetic contactor
e) DC reactor
* For c) ~ e), refer to "Individual Parts Failure Judge-
ment Methods."
a) As there is a possibility of instantaneous short
circuit generated, find the mark of the short circuit
for repair.
b) When a) is not applicable, the compressor may be
faulty.
The ground fault of inverter output/compressor can
be supposed.
Disconnect the wiring to the compressor and check
the insulation resistance of the following parts with
a megger.
a) Compressor terminals.
b) Inverter output.
-144-