68 Rockwell Automation Publication 7000-UM202D-EN-P - May 2018
Chapter 2 Power Component Definition and Maintenance
Table 3 - SGCT/snubber resistance values
SGCT Anode-to-Cathode (Sharing) Resistance
The anode-cathode resistance check measures 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, so 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.
There is a test point inside the PowerCage module 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.
Place one probe of the multimeter on the test point and the other probe on the
appropriate heatsink to determine the value of the resistor or capacitor. See
Figure 54
.
Figure 54 - SGCT PowerCage Module
SGCT Resistance Measurement Measured Resistance
Inverter Rectifier (AFE only)
SGCT Anode-Cathode Resistance (heatsink to heatsink) k-Ω
(Lowest) (Highest) (Lowest) (Highest)
Snubber Resistance (Test point: heatsink above) Ω
(Lowest) (Highest) (Lowest) (Highest)
Snubber Capacitance (Test Point – heatsink on Right) µF
(Lowest) (Highest) (Lowest) (Highest)
Resistance value between two
heatsinks is sharing resistance in
parallel with anode-cathode
resistance
Resistance value between
heatsink and test point is
snubber resistance
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