Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 263)

TROUBLESHOOTING 10-21
1557-UM050F-EN-P – June 2013
Power Semiconductor Replacement
If a device is found to be faulty, you must replace all devices in that leg. The devices are matched for
characteristics at the factory, ensuring proper operation. Mixed characteristics may cause premature
failure in the drive. This does not apply to diodes.
Replacing Thyristors - Line side converter
NOTE: Before disconnecting any leads from the circuit, note all lead connections for reassembly.
1. Remove Line side converter Heatsink Stack Assembly from Drive
Disconnect the Gate(G), Cathode (C) and Diagnostic (D) leads from the SCR 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 inch. 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 at the heatsink and snubber capacitors. The snubber resistors are mounted on the right side of
the heatsink stack assembly.
2. Heatsink Stack Removal
Remove 3/8" nut and bolt, which connect copper bus and the heatsink stack bus link. Disconnect the
incoming cables at the heatsink. 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 carefully. Extract heatsink stack completely with snubber capacitors 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: Heatsink Stack is heavy and it is preferred that two people
should extract the heatsink stack from the drive. Always check the
snubber and sharing/diagnostic resistors after removal of the stack and
then follow the next step.
3. Loosen the Heatsink Stack
There are two styles of the heatsinks and each has different procedure to loosen the tension-adjusting
nut to get the devices out of the heatsink.
New Style 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 Figures 10.2 and 10.6.