Mitsubishi Electric R410A, Service Handbook

Page: 283 / 346

[8-9 Troubleshooting Inverter Problems (TLMU) ]
- 274 - HWE14080 GB
8-9-15 Troubleshooting Problems with Diode Stack
(P168 model)
Measure resistances between each pair of terminals on the diode stack with a tester, and use the results for troubleshooting.
For cautionary notes on measuring diode stack resistance and information on the types of testers to be used, refer to the fol-
lowing page(s). [8-9-14 Troubleshooting Problems with Intelligent Power Module](page 273)
8-9-16 Troubleshooting Problems with IGBT Module
(P72, P96, P120, P144 models)
Measure the resistances between each pair of terminals on the IGBT with a tester, and use the results for troubleshooting.
The terminals on the INV board are used for the measurement.
1) Notes on measurement
Œ
Check the polarity before measuring. (On the tester, black normally indicates plus.)
Œ
Check that the resistance is not open (
ȍ
) or not shorted (to 0
ȍ
).
Œ
The values are for reference, and the margin of errors is allowed.
Œ
The result that is more than double or half of the result that is measured at the same measurement point is not allowed.
Œ
Disconnect all the wiring connected the INV board, and make the measurement.
2) Tester restriction
Œ
Use the tester whose internal electrical power source is 1.5V or greater
Œ
Use the dry-battery-powered tester.
(The accurate diode-specific resistance cannot be measured with the button-battery-powered card tester, as the applied volt-
age is low.)
Œ
Use a low-range tester if possible. A more accurate resistance can be measured.
Judgment value (reference)
Black ( + ) External view
+ (P) - (N) to (L1) to (L2) to (L3)
Red (-)
+ (P) - - 5 - 200
ȍ
5 - 200
ȍ
5 - 200
ȍ
- (N) - -
to (L1) 5 - 200
ȍ
- - -
Internal circuit diagram
to (L2) 5 - 200
ȍ
- - -
to (L3) 5 - 200
ȍ
- - -
L1 L2 L3
+
-
L1
L2
L3