Rockwell Automation Publication 7000-UM202D-EN-P - May 2018 73
Power Component Definition and Maintenance Chapter 2
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.
1. Isolate and lock out all power to the drive.
2. Note the position of the fiber optic cables for assembly. 
3. To remove the SGCT, remove the gate driver power cable and fiber optic 
cables. Exceeding the minimum bend radius (50 mm [2 in.]) of the fiber 
optic cables may result in damage.
Remove the SPS snubber connector (J1 on the SPS board) and remove 
the SPS mounting bracket with the SPS board, if installed.
4. Remove the load on the clamp head assembly as described under 
Checking Clamping Pressure
 on page 93. 
5. Two brackets secure the board to the heatsink. Loosen the captive screws 
to free the circuit board. If necessary, adjust the position of the heatsinks 
to move the SGCT freely. 
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
ATTENTION: To prevent electrical shock, disconnect the main power before 
working on the drive. Verify that all circuits are voltage-free using a hot stick 
or appropriate voltage-measuring device. Failure to do so may result in injury 
or death.
ATTENTION: You may damage the fiber optic cables if you strike or bend 
them sharply. The minimum bend radius is 50 mm (2 in.). The connector has 
a locking feature that requires pinching the tab and gently pulling straight 
out. Hold the component on the printed circuit board to prevent damage.
IMPORTANT Nylon screws are installed on the 6600V heatpipe model only; these must be 
removed when replacing the SGCTs. The purpose of these screws is for 
additional support while in transit and they are not required once the drive is 
installed on site. They must not be used again when the SGCTs are replaced.