Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - Classic Control - Manual (Page 335)

Component Definition and Maintenance 6-45
7000 “B” Frame 7000-UM150I-EN-P – June 2013
Resistance measurements
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 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 appropriate heatsink to determine the value of the resistor or
capacitor. See Figure 6.32.
Resistance value between heatsink
and test point is snubber resistance
Resistance value between 2
heatsinks is sharing resistance
parallel with anode-cathode
resistance
.
Figure 6.32 – Resistance Measurements SGCT PowerCage