Rockwell Automation 7763 Medium Voltage OneGear SMC Flex Motor Controller (10-15 kV) - Manual (Page 110)

110 Rockwell Automation Publication 7760-UM001D-EN-P - October 2014
Chapter 8 Troubleshooting
7. Refer to Figure 47 (PowerBrick Component Locations - Top View. Once
the PowerBrick has been removed, remove the "HS2" wire from the top of
the center heatsink to isolate the SCRs from the snubber and sharing
resistors. Unplug the SCR gate connectors from the gate driver boards.
Measure the DC resistance between the center and either end heatsink.
The value should be greater than 100 k. If so, and the gate-cathode
resistance is between 4-40 , the SCRs do not need to be changed. If the
resistance is very low (< 4 ), an SCR has failed and must be replaced. Note
the Match Band character from the front of the PowerBrick, and refer to
Appendix C for replacement parts.
Figure 47 - PowerBrick Component Locations — Top View
8. If the SCRs are healthy, measure the DC resistance from "S1" on the upper
gate driver board to "CS" as shown in
Figure 47 (same as above). The
connection to "CS" is made at the hex socket head screw that protrudes
through the round plastic feature at the top of the snubber capacitor. This
resistance should be 60 ±6. If a capacitance meter is available, connect
from "CS" to "S2" on the lower gate driver board. The snubber capacitor
should be 0.68 ±.04μF. If a capacitance meter is not available, an ohmmeter
may be used, and should ramp up to >2 MΩ over several seconds. (This
method does not ensure that the capacitor is healthy, but will show if it is
shorted or open.) If the snubber components are suspect, repair or replace
the PowerBrick. Refer to Appendix C for replacements parts.
HS2 HS3
RR1
RS1
Gate Driver Board
RS2 RS3
HS2 HS3
CS
RR2