Rockwell Automation 7000 PowerFlex Medium Voltage (B Frame) Commissioning - ForGe (PanelView 550) - Manual (Page 68)

64 Rockwell Automation Publication 7000-IN006B-EN-P - May 2013
Chapter 5 Commissioning the Drive
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
as shown below:
Figure 39 - 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, a detailed replacement
procedure is located the PowerFlex 7000 ‘B’ Frame User Manual’s “Component
Definition and Maintenance” section.
Test points for gate-to-cathode
resistanced on Phoenix connector
Disconnect SCR Phoenix
connector from board.