Rockwell Automation Publication 7000-UM202H-EN-P - November 2023 69
Chapter 2 Power Component Definition and Maintenance
Figure 60 - Snubber Capacitor Test (Shown with SPS Board Installed)
See Table 6 on page 64 to determine the appropriate snubber capacitance value
for the current rating of the SGCT used.
The capacitance measured is actually affected by the snubber capacitor and
other capacitance in the circuit, including capacitance from the gate driver
circuit. You are actually looking for a consistent reading for all devices.
If the capacitor is out of tolerance, see page 76
for detailed instructions on how
to replace the snubber capacitor.
Replacing the SGCT
The SGCT (“device”) with attached circuit board is located within the
PowerCage module assembly. Replace SGCTs in matched sets (two sets for
4160V, three sets for 6600V).
The SGCT and associated control board are a single component. Never change
the device or the circuit board individually. This table describes the functions
of the four LEDs on the SGCT.
Heatsink
Heatsink
Snubber
Resistor
Snubber
Capacitor
Sharing Resistor
J1
SPS Board
1
2
SGCT
Test Point
Snubber Capacitor Wire
Use Connector Terminal Screw
for Testing Snubber Capacitor
SGCT Cathode Wire
Snubber Test Point
LED 4 Green Solid Green indicates that the Power Supply to the Card is OK
LED 3 Green Solid Green indicates that the Gate-Cathode resistance is OK
LED 2 Yellow LED ON indicates the gate is ON, and Flashes alternately with LED 1 while gating
LED 1 Red LED ON indicates the gate is OFF, and Flashes alternately with LED 2 while gating
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