ABB DCT880, Service Manual

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Thyristor diagnosis
In addition, the thyristor diagnosis provided by the firmware can be used:
− Under construction.
How to find a faulty thyristor
If a blown fuse is suspected, the problem is caused most often by a faulty thyristor. To make sure, that a
thyristor is the reason and needs to be exchanged fault tracing must be done.
In general make sure, that all Safety instructions given within this manual or within the
safety instructions, related to the application itself, are obeyed.
Standard thyristor power controllers size T1 … T4 (20 A ... 740 A), wS500
Standard thyristor power controllers, wS500. External semiconductor fuses are required.
− The thyristor power controller must be disconnected from the mains.
Blown fuses
− Using the OHM function of a normal multimeter, measurements must be made from both sides of the
semiconductor fuses (e.g. L1 to U1, L2 to V1 and L3 to W1):
Faulty thyristor
− Using the OHM function of a normal multimeter, measurements must be made from both sides of the
thyristor power controller (e.g. U1 to U2, V1 to V2 and W1 to W2).
− Normally, each measurement should show high resistance (> 1 k Ω ).
− Target: find a short circuit, indicated by low resistance (< 1 Ω ) (destroyed thyristor).
− If the Thyristor power controller is designed with thyristor modules, then a module consists of two
thyristors. In this case, it is sufficient to know which thyristor module has a defective thyristor because the
complete module must be replaced.
− After a thyristor module is replaced, the above-mentioned measurement should be done another time to
make sure that all faulty thyristors have been detected!
Fault Tracing Thyristors
3ADW000449R0101 DCT880 Service Manual e a