54
Exchange of Thyristors for Size D6
3ADW000195R0501 DCS800 Service Manual e e
Note:
The Faston connectors of the gates are of different size.
Gate A should always be in front of the clamped heat sinks due to cooling reasons.
Location of BCT’s gate A when built in
Find faulty thyristor
1. Find the defective branches by performing an OHM test (both polarities)
between U1, V1, W1 and C1, D1 (see picture Anti-parallel B6-bridges with
branching fuses on page 45).
2. Disconnect the branching 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 which thyristor is broken change only one thyristor, clamp the heat sinks
again and repeat step three.
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