Rockwell Automation 7000A PowerFlex Medium Voltage AC Drive - Air-Cooled (A Frame) - Manual (Page 276)

5-34
Component Definition and Maintenance
7000A-RM001A-EN-P – January 2011 7000 “A” Frame
Replacing Sharing Resistor
Normally the sharing resistor is part of the snubber resistor assembly.
Replacement of the sharing resistor will require replacing the snubber
resistor also.
The sharing and snubber resistors are normally located on the backside of
the PowerCage. See the instructions for removing and replacing snubber
resistors.
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 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. (See Figure 5.28.)
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.
Resistance value between heatsink
and test point is snubber resistance
Resistance value between 2
heatsinks is sharing resistance
in parallel with anode-cathode
resistance
Figure 5.28 – Resistance Measurements SGCT PowerCage
Sharing Resistors
(cont.)