Chapter 6 - Exchange of Thyristors for Size A6
DCS 500 / DCS 600 Service Manual
VI A
6 - 3
Find faulty thyristor
1. Find the defective branches by performing an OHM test (both
polarities) between U1, V1, W1 and C1, D1 (
2. Disconnect the branch fuses of the defective branches.
3. Find the defective thyristors by performing an OHM test (both
polarities) over their heat sinks.
4. In a 4 - quadrant converter with BCT’s change the BCT.
5. In a 4 - quadrant converter with 2 single thyristors change both
thyristors clamped between the same heatsinks at once.
Note
: Because “Disc Type” semiconductors need a certain
compression force to operate properly a measurement outside
the clamped heat sinks might be wrong. To be sure change only
one thyristor, clamp the heat sinks again and repeat step three.
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