Vlt drive is stopping frequently.

Hi guys,
We have 15 vlt drive(danfoss) which is controlling by profibus and s7 300 plc.my questions is here sometimes
Any one vlt drive is stopping without any fault alarm and we restart and working normal.we don't understand why vlt is going off?
Always fault is not coming in same drive.
Kindly could you guide me how can solve this issue.

Kind regards.
Jamal.

Sounds like you may be sending a normal stop command to the drive.

Would you normally stop this motor with a push button? If so, check the wiring.

Would you normally stop this motor with a command over the Profibus communications? If so, ensure this command is not being sent unknowingly.

Hi Agill,
Thanks for your reply.
I would like inform you that we are not stopping the motor by pressing push button switch. We started the motor from him and during running time we don't need to stop the motor but now it is stopping automatically and message coming on the Hmi that vlt drive 1 failure.
Thanks for your valuable time.
Please help me.
Kind regards.
Jamal.

Hi Agill,
When motor stopped with fault that time I found below message on the Hmi screen
TRANSFER BELT 3 96U /96 M2 (PLUG?!).
I checked 96 u2 vlt drive but there was no any fault. I don't understand what mean PLUG?!.
We reset and start and working normal.
Please help me why this fault is coming.
Kind regards.
Jamal.

That is a question only the programmer can answer. Usually, this is part of the documentation package for the equipment. Did you try there? If that message is undocumented, you need a better supplier...

Something in your PLC is getting a signal, or INTERPRETTING a signal, as whatever "Plug" means. Since we can only guess, my guess is that "Plug" might refer to a jammed product on your conveyor, often detected via a rapid increase in motor current. The drive is capable of doing this, but by using the Profibus connection, your PLC is also capable of doing this simultaneously. It could be that the programming in the PLC is set to a lower threshold than that of the VFD, so the PLC is tripping in anticipation.

But again, nobody here can tell you anything definitive, unless by shear coincidence the person who wrote your programming for the PLC/HIM happens to be reading this and it able to recognize it.