Dear all,
Can anyone help me to diagnosing the below problem?
As maintenance engineer in a sugar factory, I have been having problem with induction motor 37Kw driven by variable frequency drive (VFD), type Vacon NXS, this motor is running normally at 1200 rpm with draw current about 8.5A, the thing is that this motor was stopped working the drive HMI shown “Saturation Trip” which was indicating the drive is gone, we changed the drive & fuses with a new one and the motor restarted.
The same problem happened yesterday for the same other motor 37Kw, I found the drive main breaker was tripped and there is abnormal sound internal the drive, I turned it ON for control supply to what is HMI showing to locate the fault and keep the drive ready for start, then the drive’s HMI was ceased to function and did not shown the parameter, after checking I found the 3-F fuses 63A was blown, motor & power cable meggering was in GO .
The question is:

• Why the fuses was blown while this motor is running normally?
• why the drive component defective when the fuses blown? while there is no over-current or
short-circuit coming through the motor or power cable.
• What is the “Saturation Trip” cause to drive?

I’m wishing hearing from you dears.