Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - ForGe Control - Manual (Page 83)

Rockwell Automation Publication 7000-UM202B-EN-P - June 2014 83
Component Definition and Maintenance Chapter 3
SCR Gate-to-Cathode Resistance
One test that can be performed on SCRs that cannot be performed on SGCTs is
a Gate-to-Cathode Resistance Test. Performing a Gate-to- Cathode resistance
measurement will identify damage to an SCR by revealing either an open or
shorted gate to cathode connection. To test an SCR from gate-to-cathode,
disconnect the SCR gate leads from the self powered gate driver board and
measure the gate-to-cathode resistance on the SCR firing card Phoenix
connector.
Figure 76 - SCR gate-to-cathode test
The resistance value from gate-to-cathode should be between 10 Ω to 20 Ω. A
value close to 0 Ω indicates that there is an internal short in the SCR. An
extremely high value indicates that the gate connection in the device has broken.
If a Gate-to-Cathode test reveals a damaged SCR, refer to page 86 for the SCR
replacement procedure.
Test points for Gate-to-Cathode
Disconnect SCR
Phoenix
connector from
board