Chapter 6 - Exchange of Thyristors for Size C3
VI A
6 - 2
DCS 500 / DCS 600 Service Manual
Remove faulty thyris-
tor
-
Remove the plastic cover in front of the heat sinks; the screws
are accessible, if the SDCS-PIN-x1 boards will be unfastened;
there is no need to disconnect the electrical connections at the
PIN-x1 boards.
-
Remove the fuse, connected to that thyristor (pair) which needs
to be exchanged.
-
Disconnect the lead of a snubber capacitor connected to the
heat sink; if the very right or left plastic cover is fixed at the heat
sink, which needs to be removed remove the screw.
-
If you have a 2 quadrant converter:
•
Loosen the screws, which keep the press clamp and the heat
sink in position; remove the heat sink, mark the direction of
the thyristor and the positition of the gate leads, then remove
the thyristor.
-
If you have a 4-quadrant type converter:
•
Always start working at that thyristor which is part of the re-
verse bride (V21, V22 a.s.o.) loosen the screws, which keep
the press clamp and the heat sink in position; remove the
heat sink, mark the direction of the thyristor and the positition
of the Gate leads, then remove the thyristor.
Find faulty thyristor
-
Perform the OHM test with both polarities. Use the DC terminal
of the antiparallel thyristors connected as one measuring point
and the remaining heat sink as the other.
Case a) If this test indicates high resistance, the remaining
thyristor is all right healthy and the one already
removed should be marked and needs to be
replaced.
Case b) If this test indicates low resistance, the remaining
thyristor is faulty and needs to be replaced.
Remove it in the way described above.
The other thyristor is ok!
-
In case a) of the OHM test described above mount a new thy-
ristor at the position of the reverse bridge.
-
In case b) of the OHM test described above a new thyristor for
the forward bridge and afterwards the thyristor of the reverse
bridge which was removed first have to be mounted.
3ADW000093R0601_DCS500B/DCS600_Service Manual_e_f
