Rockwell Automation 7000L PowerFlex Medium Voltage AC Drive (C Frame) - Classic Control - Manual (Page 386)

6-42 Component Definition and Maintenance
7000L-UM300I-EN-P – June 2013 7000 “C” Frame
Testing Snubber Resistors
Access to the snubber resistor is not required to test the resistance.
Located within the PowerCage under the chill block is a snubber
resistor test point. For each device, there is one test point. To verify
the resistance, follow the procedures outlined in Chapter 4.
Measure resistance
between chillblock
and test point. Measure resistance
between chillblock
and test point.
Figure 6.33 – Testing the Snubber Resistor
Sharing Resistors
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 may be shorted. The
anode to cathode resistance check will be 0 Ω for a complete short,
but SGCT can fail when partially shorted.
Sharing resistors provide equal sharing of the voltage when matched
devices are used in series. Sharing resistors in SCR PowerCages
provide a diagnostic function.