Rockwell Automation 7000L PowerFlex Medium Voltage AC Drive (C-Frame) - ForGe Control - Manual (Page 307)

Rockwell Automation Publication 7000L-UM301D-EN-P - June 2014 307
Component Definition and Maintenance Chapter 5
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.
Figure 255 - 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.
Measure resistance
between chillblock
and test point. Measure resistance
between chillblock
and test point.