Mitsubishi Heavy Industries FDT71VNXVD Service Manual page 41

(7) Power transistor module (including the driver PCB) inspection procedure
transistor module
cracked or burnt?
short circuit between the
power transistor module
Compressor operation
Is there any difference in
the compressor current
between phases?
* 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
NO
Is there a
YES
terminals? 1
NO
YES
If there is a 10% or greater difference
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 controller
incorporated.
Tester
Terminal Terminal
Model 71
(+) (-)
P N
(Numerical
N P
value rises.)
P U
Several M
P V (Numerical
value rises.)
P W
N U
N V Approx. 650 k Approx. 1.2 M
N W
U P Approx. 670 k
V P Approx. 4.4 M
W P Approx. 4.4 M
U N Approx. 650 k
V N Approx. 4.8 M
W N Approx. 4.9 M
If the measured values range from 0 ~ several kW, there is a possibility
that the elements are damaged, so replace the power transistor parts.
- -
41
'10 • PAC-SM-137A
Replace the outdoor
unit inverter PCB
Normal values (Ω)
Model
100~140
0 ~ Approx. 1 M
Approx.
300~400
0
Approx. 1.3 M
0