Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 266)

10-24 TROUBLESHOOTING
1557-UM050F-EN-P – June 2013
Replacing Thyristors - Machine side converter
1. Remove Machine side converter Heatsink Stack Assembly from Drive
Disconnect the Gate(G), Cathode (C) and Diagnostic (D) leads from the GTO gate driver boards.
Disconnect the fiber optic leads, D.C Power leads to the gate driver and power supply boards.
Disconnect leads on the thermistor board (if applicable). Remove the circuit board mounting glastic
plate using ¼ in. hardware. To access the center phase machine side converter, the door mullion
steel channel can be removed for better access.
Before disconnecting any lead, please note all lead connections for re-assembly. After removing the
circuit board mounting glastic plate, disconnect the sharing/diagnostic resistors from the heatsink.
These resistors are mounted on the left side of the heatsink stack. Disconnect the snubber resistor
leads from the heatsink and snubber capacitors. The snubber resistors are mounted on the right side
of the heatsink stack assembly.
2. Heatsink Stack Removal
First remove 3/8" nuts at bottom and then top of heatsink stack-mounting bracket insulator. While
taking the top nuts out, make sure that the heatsink stack is handled very carefully because the
sharing/diagnostic and snubber resistor are very close to the stack. Little care may cause the damage
to these resistors by touching the stack with the resistors while taking the stack out of the drive.
Extract heatsink stack completely with snubber capacitor and diode from the drive without touching
the snubber and sharing/diagnostic resistors. Lay down the flat surface (left side) of the heatsink stack
on a flat surface.
CAUTION: The heatsink stack is heavy. Use two people to remove
the heatsink stack from the drive. Failure to do so may result in injury
to personnel and/or damage to the equipment.
3. Loosen the Heatsink Stack
Loosen completely the tension-adjusting nut of the clamp head assembly (see Figure 10.2). Open-end
wrench is required to rotate the load-adjusting nut. Pry apart the heatsink to take the devices out.
CAUTION: Never rotate the outer nut on the top of the indicating disc.
The rotation of the outer nut will effect the torque calibration. Only
loosen the tension-adjusting nut. Refer Figure 10.2 and 10.6.
The machine side heatsink stack can be viewed in Figure 10.3.