Rockwell Automation 7000A PowerFlex Medium Voltage Drive (A-Frame) - Classic Control - Manual (Page 210)

4-36 Commissioning
7000A-UM150F-EN-P – June 2013 7000 “A” Frame
An SCR that has failed from anode to cathode will commonly produce
a resistance value of 0 for a shorted device or ∞ Ω for an opened
device. Unlike the SGCT, it is highly irregular for an SCR to have a
partially shorted device. If an SCR is found to be out of tolerance,
refer to Chapter 6 – Component Definition and Maintenance for
detailed instructions on how to replace the SCR assembly.
SCR Sharing Resistance Test
To test the sharing resistor of an SCR module, disconnect the 2-pole
plug of the self-powered gate driver board labeled SHARING and
SNUBBER on the circuit board. The red wire of the plug is the
sharing resistor. Measure the resistance between the red wire of the
plug and the heatsink to the left. A value of 80 k-ohms indicates a
healthy sharing resistor.
Resistance between heatsink and
red wire at plug is sharing resistance
Figure 4.9 – SCR Sharing Resistance Test