25
Fault Tracing Thyristors
3ADW000488R0101 DCS880 Service manual e a
12. Measure fuses F401 … F403 using the
OHM function of a normal multimeter and
exchange the broken ones.
13. The SDCS-BAB-F0x contains a 3-phase half-controlled bridge (B6H).
Using the OHM function of a normal multimeter, measurements must be made from each AC terminal to
each field exciter terminal (U1* to F+, V1* to F+, W1* to F+, U1* to F-, V1* to F- and W1* to F-).
− Normally, each measurement
should show high resistance (> 1
kΩ).
− A short circuit is indicated by a low
resistance (< 1 kΩ, destroyed
thyristor or diode).
− If one of the measurements shows
a short circuit, replace the
SDCS-BAB-F0x.
− A measurement, showing less resistance than 1 Ω should be made for a second time. Apply the
test leads with opposite polarity; if this measurement shows the same result, the SDCS-BAB-F0x is
faulty and needs to be replaced.
− After the SDCS-BAB-F0x is replaced, the above mentioned measurement should be done another
time to make sure that all is fine.
Exchange SDCS-BAB-F0x and fuses
Exchange the SDCS-BAB-F0x continue with chapter Remove faulty SDCS-BAB-F0x
.
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