Siemens SINAMICS DCM Manual page 599

Descriptions of functions
10.33 Diagnostics
Thyristor diagnostics comprises two parts:
1. Checking the thyristor for its blocking capability
All thyristors are individually fired and it is not permissible that current flows. If it does, this
indicates that a thyristor is fused or it triggers with forward breakover or a ground fault
has occurred, i.e. terminal 1C or 1D is connected to ground.
NOTICE
Ground leakage circuit breaker
In IT systems (i.e. in systems with an ungrounded neutral point of the supply
transformer), the thyristor diagnostics cannot detect a single-pole ground fault.
For these types of line supply, it is recommended that a ground fault monitor is used.
Impermissible operation with ground fault
The type and location of the fault cannot be established just from a ground fault error
message. In the event of continued operation, serious aftereffects all the way to electric
arcs are possible. This can result in death, serious injury or material damage.
If a ground fault occurs during operation, the system must be switched off immediately.
Then identify and eliminate the source of the ground fault.
The plant operating company is responsible for the consequences for further operation
after a ground fault has been detected. Carry out a risk analysis.
2. Checking that the thyristors can be triggered
All of the thyristors are triggered in pairs and in this case, a current must flow (as a
minimum, 5% of r50072[1]). Otherwise, a thyristor cannot be triggered. This can also be
caused by a fault in the firing pulse generation.
NOTICE
Possible rotation of the motor shaft.
The low current that flows during this test can cause the motor to briefly rotate for
motors that are very easy to move and are not loaded, as in this operating state, the full
field is already present.
Faults that are detected result in fault message F60061. The fault value provides information
as to which thyristor was detected to be defective and what the possible cause of the fault
could be.
600
WARNING
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SINAMICS DCM DC Converter
Operating Instructions, 02.2015, A5E34763375/RS-AA/001