Rockwell Automation 7000A PowerFlex Medium Voltage Drive (A-Frame) - Classic Control - Manual (Page 209)

Commissioning 4-35
7000 “A” Frame 7000A-UM150F-EN-P – June 2013
SCR Anode to Cathode Resistance
Performing an Anode to Cathode resistance test verifies the integrity
of the SCR. Unlike the SGCT, the SCR uses the snubber circuit to
power the self-powered gate driver boards. The resistance
measurement taken across each SCR should be consistent; an
inconsistent value may indicate a damaged sharing resistor, self-
powered gate driver board or SCR.
Using an ohmmeter, measure the anode to cathode resistance across
each SCR in the rectifier bridge, while looking for similar resistance
values across each device. Easy access from the anode to cathode is
available by going from heatsink to heatsink as shown in the diagram
below:
Resistance value between 2 heatsinks
is Anode to Cathode resistance
Figure 4.8 – Anode to Cathode Test
A good SCR and circuit should read between 22 and 24 kΩ.