6RA70: F30 fault details

[engstreet]

Hi,

I have a 1200 A 6ra70 drive installed running a single DC motor (rated Amperes: 1000) that drives a screw feeder. The drive takes setpoint from a pressure controller and adjusts rpm accordingly. In the last month the drive has tripped twice during normal operation. On both occasions, the fault displayed was F30: Commutation failure or overcurrent has occured.

When the first tripping occured, the screw which the motor shaft turned was jammed leading to high current. Hence the assumption was that the drive tripped on overcurrent. However checking the detailed fault description in r047.001 showed the value 4 which is described as:

A paralleled SIMOREG DC-MASTER has detected a
commutation failure or overcurrent


I was expecting the value 3 which is described as:

The maximum current value was higher than 250% of the
actual rated device current according to r072i002 (960 A)


When the second tripping occurred a couple of weeks later, the same fault and error value was generated. However resetting the fault and starting the drive again led to normal resumption of process with current in normal running range of 500-560 A. The nature of the process makes the screw feeder susceptible to jamming in case temperature falls below the specified setpoint hence jammed screw feeder is suspected to be the cause of tripping again.

However the error value of 4 in r047 makes me suspect that the root cause is different. There is no paralleled drive with the 6ra70 converter hence the value of 4 makes no sense. Can someone shed some light as to what could be the possible causes of this F30 fault?

[TMS320F2812]

Pls. check cable trigger all SCRs.
I found one cable (Kathod) of one SCR broken at location of cable tie to strap all cable trigger SCR.