Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 264)

10-22 TROUBLESHOOTING
1557-UM050F-EN-P – June 2013
Old Style Heatsink stack
In old style heatsink stack the steel clamping rods are used, see Figure 10.7. Remove the two nuts at
the top of the rod shown in Figure 10.7. Replace the silicon if used in the caps of the nuts. After
removal of these two nuts the top pressure bar assembly can be removed. Heatsink segment can now
be moved so that SCRs can be replaced. Note the orientation of device leads before re-assembly.
4. Replacement of SCRs
Remove the new device from the packing. Don‟t handle the device by holding its leads. Ensure the
face of the new device is free from dirt. Use a clean, lint free cloth to place a thin film of grease (Alcoa
EJC No.2) to both side of the device. Replace SCRs with the appropriate matched set noting the
orientation of the SCRs. Ensure that locating pins are in place in the heatsinks and that the pins seat
properly in the center of each device. Ensure that the orientation of the S.C.R. leads is the same.
Tighten the tension adjusting nut (on new style) or two steel clamping rod nuts (on older style),
monitor devices ensuring they are centered on the pins of the heatsink. This can be checked, by
rotating devices to see if the are centered on the pins.
CAUTION: Never check the rotation of the device by rotating its leads.
Check the rotation of the device by rotating the device itself. Don‟t
apply any force on the leads.
5. Reassembly of Heatsink Stack Assembly

New Style Heatsink stack
In new style heatsink, rotate the tension-adjusting nut to reassemble the stack. Tighten the
tension-adjustment nut until the indicating disc washer is just able to turn freely with your fingers.

Old Style Heatsink stack
Replace clamp pressure bar assembly on heatsink stack, torque outer M16 clamp nuts finger
tight. Before further torquing, ensure that the bottom heatsink mounting bracket‟s mounting
surface extends .50 inch beyond heatsink rear surface (the front channel face of the bracket will
align with the front surface of the heatsinks). Also ensure that the glass epoxy rods do not touch
any part of the heatsinks (temporary spacers may be required).
When the M16 nuts are torqued in place the distance from the top pressure bar to the bottom
pressure bar should be equal from front of the clamp to the back of the clamp to within 0.2mm
(.008 in.).