Chapter 7 - Exchange of Thyristors for Size C4
VI A
7 - 2
DCS 500 / DCS 600 Service Manual
Find faulty thyristor
-
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.
Remove faulty thyris-
tor
-
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
