120 KW VFD for id fan application:  VFD During running time, some times motor may stop its operation without stop command. if anyone having the detail answer please share .

The motor is possibly stalling or a contactor between the drive output and the motor may be opening up. What type of vfd is it?

Motor rpm 3600?

Not enough information provided. Is this a PWM or older Six Step VFD? Are there any trip indications or does the drive do a controlled stop? What type of interface controls the drive start stop circuit? Can you provide the Drive Model and basic Motor Data?

Typically most firmware has protective features built it to protect the drive from current problems. If your drive is faulting, the drive firmware may be seeing some sort of overload or mechanical problems. Check the status parameters in your drive at the time of your fault. This may help you diagnose the issue more fully.

Fault code from the VFD needed, Brand VFD and model/age. Possibly voltage issue, same time everyday or occurrence? Grounding, voltage, signal?
Will drive reset and run or is complete power down/up required to reset major fault?

Please give us more details to try give you a hand. (Brand, topology, type of motor among others).

Regards!

Most likely the connections need to be tighten.