Rockwell Automation 7000L PowerFlex Medium Voltage AC Drive (C Frame) - Classic Control - Manual (Page 242)

Commissioning 4-37
7000 “C” Frame 7000L-UM300I-EN-P – Juen 2013
A good SCR and circuit should read between 22 kΩ and 24 kΩ.
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 chill block to the left. A value of 80 k-ohms indicates a
healthy sharing resistor.
Red Wire at
2-pole connector
Snubber Test Point
Red Wire at
2-pole connector
Snubber Test Point
Figure 4.9 – SCR Sharing Resistance Test