Find Faulty Thyristor - ABB DCS 500B Service Manual

Chapter 9 - Exchange of Thyristors for Size C4

Find faulty thyristor

Remove faulty thyris-
tor
VI A
9 - 2
- Find the defective branch(es) by performing an OHM test (both
polarities) between U1, V1, W1 and C1, D1
- 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
ristor 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
need not be loosened .
- Remove the thyristor.
3ADW000093R0701_DCS500B/DCS600_Service manual_e_g
(see Figure
(see Figure 9-2) at the top of the thy-
(see Figure 9-1). The copper bars
DCS 500 / DCS 600 Service Manual
5-1).