Rockwell Automation 7000A PowerFlex Medium Voltage AC Drive (A Frame) - ForGe Control - Manual (Page 72)

72 Rockwell Automation Publication 7000A-UM200C-EN-P - June 2014
Chapter 3 Component Definition and Maintenance
SGCT Anode-to-Cathode Sharing Resistance
The anode-cathode resistance check will measure the parallel combination of the
sharing resistor and SGCT anode-cathode resistance. The sharing resistor has a
resistance much lower than that of a good SGCT, thus the measurement will be
slightly less than the resistance of the sharing resistor. A measurement between 60
kΩ and 75 kΩ indicates the SGCT is in good condition and that wiring to the
SGCT is correct. If the SGCT fails, it will be in the shorted mode, 0 Ω. The
anode to cathode resistance check will be 0 Ω.
A test point is provided inside the PowerCage to measure the resistance of the
snubber resistor and capacitance of the snubber capacitor. The test point is the
electrical connection between the snubber resistor and snubber capacitor. The
procedure is to place one probe of the multi-meter on the test point, and the
other probe on the anode heatsink in order to measure the snubber resistor value
and the snubber capacitor (
Figure 57 ). Remove the snubber terminal connection
to TB1 of the SPGD board and measure between the test point and the wire that
is connected to pin 1 of the TB1 female connector. Replace the snubber terminal
connection once the measurement is complete.
Figure 57 - Resistance Measurements SGCT PowerCage (SPS Board removed for clarity)
Resistance value
between two heat sinks
is sharing resistance in
parallel with anode-
cathode resistance
Resistance value
between heat sink
and test point is
snubber resistance