ABB DCS 500 Series Service Manual page 46

Chapter 7 - Exchange of Thyristors for Size C4
Find faulty thyristor
Remove faulty thyris-
tor
VI A 7 - 2
- Find the defective branch(es) by performing an OHM test (both
polarities) between U1, V1, W1 and C1, D1 (see Figure 5-1 ).
- Remove the screws of the left and right branch fuses. Remove
the busbar, leading to the AC connection, too (not necessary at
2-quadrant converters, left version!).
- If you have a 4-quadrant converter:
• Remove the screws of the DC busbar either above or below
the blown fuse.
Note: the connection is made with a screw socket, which
may fall down, if the last screw is removed.
• Put a small piece of isolator (paper, cardboard, plastic, etc.)
between the DC busbar and the heat sink.
• Perform the OHM test with both polarities between the DC
busbar and the heat sink as the second measuring point.
• Now perform the OHM test with both polarities between the
isolated heat sink and the heat sink, which was connected to
the fuse as the second measurement point.
• Depending on the result, the thyristor located between the
measuring terminals of the first test or the second one needs
to be removed.
- If the thyristor is partly covered by a fuse, loosen the screws and
move the fuse some centimeters up or down; fix the fuse.
- Remove the gate leads if possible.
- Loosen the mounting clamp (see Figure 7-2 ) at the top of the
thyristor stack.
Attention: While loosen the mounting clamp the indicating spring
must be pulled out a little, otherwise the spring will be damaged!
- Attach the disassembly tool at the faulty thyristor and prise open
the upper and lower heat sinks (see Figure 7-1 ). The copper
bars need not be loosened .
- Remove the thyristor.
3ADW000093R0601_DCS500B/DCS600_Service Manual_e_f
DCS 500 / DCS 600 Service Manual