Chapter 2 - Checking IGCTs and Diodes ABB
2-2 (6) 3BHS202077 ZAB E01 Rev. C ACS 6000 Maintenance Manual
Note: When checking be careful not to disconnect the fiber optic cable
while the IGCT is energized to prevent an undefined control state.
3 Test the IGCT by measuring the voltage between gate and cathode.
Note: When measuring be careful not to shorten gate and cathode/anode
of the IGCT. A short circuit will destroy the semiconductor.
Figure 2-2 Testing IGCTs
To avoid shortening gate and cathode:
• Use short tipped probes
• Hold one probe against the cooler on the cathode
side and the other probe against a screw head on the
gate side (see
Figure 2-2
).
Result of the measurement: approx. -20 VDC (see
Figure 2-2
).
4 Disconnect the power supply of the gate unit (one of the following
circuit breakers in COU: -Q1041, -Q1042, -Q1043, see wiring dia-
gram).
5 Wait approx. 20 sec. for the capacitors of the gate unit to discharge.
Step 2
1 Verify that the power supply of the gate unit is off.
2 Switch off the auxiliary power supply pertaining to the INT board in
the cabinet.
3 Connect a temporary fiber optic cable at one end to the gate unit and
at the other end to a permanent light transmitter of the INT board.
• Inside ARU: connector A714 (see
Figure 2-3
)
• Inside INU: connector A712 or A713 (see
Figure 2-3
)
Cathode
Gate
Measuring results:
Step 1: -20 VDC
Step 2: +0.7 VDC
Side view
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