21
Fault Tracing Thyristors
3ADW000488R0101 DCS880 Service manual e a
Ripple monitor
If the ripple monitor fault occurred, a fault tracing as described above must be carried out:
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Check the fuses and the thyristors, according to the statements before.
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If the power section seems to be ok, but still one or more thyristors don’t take current, something went
wrong in between the firing pulse generation and the thyristor’s gate; in this case check:
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Is a firing pulse present on the primary side of the firing pulse transformer?
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Is a firing pulse present on the secondary side of the firing pulse transformer?
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Is the firing pulse transferred to the gate of the thyristor (loose gate connector)? Are all electrical
connections still healthy?
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Can the thyristor be fired with the applied firing pulse? Is the pulse form of the firing pulse identical at
all measuring positions?
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Check the settings of the current controller.
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Check the AC mains network by taking recordings of the line voltage and current at all 3 phases at the same
time.