Mitsubishi Electric PUHY-HP120TNU-A, Service Handbook

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[8-9 Troubleshooting Inverter Problems ]
40
- chapter 8 HWE18240_GB
8 Troubleshooting Based on Observed Symptoms
8-9-14 Troubleshooting Problems with IGBT Module
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.