45
Exchange of Thyristors for Size D5
3ADW000195R0501 DCS800 Service Manual e e
Find faulty thyristor
1. Find the defective branches by performing an OHM test (both polarities)
between U1, V1, W1 and C1, D1 (see fig. Anti-parallel B6-bridges with
branching fuses on page 45)
C1 (+)
D1 (-)
U1
V1
W1
branching fuse
branch
F11 F13 F15
F14 F16 F12
V11 V13 V15V24 V26 V22
V14 V16 V12V21 V23 V25
principle_B6_a.dsf
Anti-parallel B6-bridges with branching fuses
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 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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