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Fault Tracing Thyristors
3ADW000195R0501 DCS800 Service Manual e e
Additionally for service and preventive maintenance
Following additional tools are mandatory for cleaning:
An ESD safe blower / ESD vacuum
cleaner (ABB Service Finland code
0006ESD / MUNTZ 555-ESD-S-E):
How to detect a faulty thyristor
Thyristor problems can be noticed differently:
A fuse is blown
This is an indication, that a strong overcurrent has happened due to one of the
following reasons:
An internal short circuit between the phases (line side) because of a defective
thyristor (short circuit inside a thyristor from anode to cathode).
An internal short circuit between the phases (line side) because of circulating
current in a 4-Q converter (malfunction of the control electronics, no thyristor
defective).
An external short circuit at the DC terminals of the converter without sufficient
impedance.
A commutation fault during generating (active braking with high current, high
EMF and with low AC voltage) of a 4-Q converter.
Note:
In case of parallel fuses: If one of the parallel fuses is blown, all parallel fuses have
to be changed. The ‘undamaged’ fuses might be ‘half-blown’ and will blow with the
next high current.
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