Mitsubishi Heavy Industries V Multi FDC71VNX Technical Manual page 168

(6) Power transistor module (Including the driver PCB) inspection procedure
short circuit between the
power transistor module
Compressor operation
Is there any difference in
the compressor current
* 1
Power transistor module terminal short circuit check procedure
Disconnect the compressor wiring, then conduct a short circuit check.
P-U, P-V, P-W
N-U, N-V, N-W
Check between the P-N terminals.
Bring the tester probes in contact with the following
places on each te rminal.
P: Power transistor P terminal,
N: Power transistor N terminal,
U: End of red harness to compressor
V: End of white harness to compressor
W: End of black or blue harness to compressor
Is the power
YES
transistor module
cracked or burnt?
NO
Is there a
YES
∗
terminals? 1
NO
YES
If there is a 10% or greater difference
between phases?
in the current in different phases.
(except during acceleration or deceleration)
NO
Normal
-
Check for a power transistor short circuit.
• When you do not have a diagnostic checker for judging if
the inverter is defective, measure between the terminals
of the power transistor parts, judge whether the power
transistor is defective or not.
• Disconnect the compressor, then measure with the
control incorporated.
Models FDC71-140VNX, 100-140VSX
Tester
Terminal Terminal
(+) (-)
P N
N P
P U
P V
P W
N U
N V
N W
U P
V P
W P
U N
V N
W N
If the measured values range from 0 - several kW, there is a possibility
that the elements are damaged, so replace the power transistor parts.
167
-
'19 • PAC-T-327
Replace the outdoor
unit inverter PCB
Normal value (W)
Model FDC71 Model FDC100-140
0 -
Approx. 1 M
(Numerical
Approx. 300-400
value rises.)
Several M
(Numerical 0
value rises.)
Approx. 650 k Approx. 1.2 M
Approx. 670 k
Approx. 4.4 M Approx. 1.3 M
Approx. 4.4 M
Approx. 650 k
Approx. 4.8 M 0
Approx. 4.9 M