ABB DCT880, Service Manual

Page: 26 / 90

26
Install new thyristor modules
1. Ensure that the new thyristor module is of the correct type (
see Appendix A
of this manual).
2. Remove old heat-conducting compound (grease) from the heat sink. Clean the mounting surfaces (heat
sink and thyristor module) with an appropriate solvent (e.g. ethanol) by means of tissue paper. When the
heat sink is clean, spread out the heat-conducting compound with a rubber spatula or by hand.
3. Apply a thin layer of heat-conducting
compound to the new thyristor module.
4. Spread the heat-conducting compound evenly by moving the thyristor module forward and backward on
the heat sink.
5. Tighten all clamping screws by hand until the screw heads touch the bottom of the thyristor module. Then
pre-torque the screws to 2.0 Nm.
Note :
If the thyristor module is mounted by means of four screws, tighten the screws crosswise.
6. Tighten the screws to nominal torque according to table Nominal mounting torque thyristor modules
.
Unit Thyristor modules Nominal mounting torque
Size Size (width) Type Electrical
connections
Thyristor module
to heat sink
T1, T2 ( ≤ 160 A) 20 mm block SKKT27B, 42B, 57B, 106B 3 Nm
5 Nm
MCC26, 44, 56, 140 2.5 ... 4 Nm 2.5 ... 4 Nm
T2 (> 160 A) 34 mm block MCC162, 200 4.45 … 5.5 Nm 2.25 … 2.75 Nm
SKKT162 5 Nm 5 Nm
T3 50 mm block MCC255, 312 11 … 13 Nm 4.5 … 7 Nm
TT250 12 Nm 6 Nm
SKKT250 9 Nm 5 Nm
T4 60 mm block TT425, 570 12 Nm 6 Nm
MCC501 10.2 … 13.8 Nm 4.25 … 5.75 Nm
MT3-540, 595 12 Nm 6 Nm
7. Reinstall the current transformer. Make sure, its position and direction is correct.
8. Reinstall the busbars. Make sure, the correct torque is applied according to table
Nominal mounting
torque for thyristor modules .
9. Reconnect all gate leads to the thyristor module.
10. Perform an OHM test to make sure the thyristor is ok.
11. Reinstall the SDCS-PIN-H board.
12. Reconnect all cables and plugs at the SDCS-PIN-H:
Exchange thyristors sizes T1 … T4
3ADW000449R0101 DCT880 Service Manual e a