Mitsubishi Electric City Multi CMB-WP108V-G, Service Manual

Page: 234 / 301

[
IX
Troubleshooting ]
- 225 - HWE1113B GB
(5) Simple checking procedure for individual components of main inverter circuit
Before inspecting the inside of the control box, turn off the power, keep the unit off for at least 10 minutes, and confirm that
the voltage between FT-P and FT-N on INV Board has dropped to DC20V or less.
(6) Troubleshooting for 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 ( ohm) or not shorted (to 0 ohm).
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.
Part name Judgment method
IGBT module See "Troubleshooting for IGBT Module ". ( IX [4] -7- (6) )(page 225)
Rush current pro-
tection resistor
R1, R5 Measure the resistance between terminals R1 and R5: 22 ohm 10%
Electromagnetic
relay
72C
This electromagnetic relay is rated at DC12V and is driven by a coil.
Check the resistance between terminals
DC reactor DCL Measure the resistance between terminals: 1ohm or lower (almost 0 ohm)
Measure the resistance between terminals and the chassis:
1
6 5
2 3 4
Upper
Installation
dire c tion
C h e ck point
C h e ck ing c riteria( ) W
Between Terminals 5 and 6
Between Terminals 1 and 2
Between Terminals 3 and 4
Not to be s h ort- c ir c uited
(Center value 75 o h m)
Coil
Conta c t