Danfoss VLT FC 100 Torque limit

Hello Guys,

i have a strange problem with some Danfoss VLT FC 100 Frequency inverters.
We have sometimes a little overload (we have to work on that), and the Motor reaches his torque load. The VLT 100 limits the output current (and frequency) and shows a warning (12 Torque limit). So far everything is normal.
Now the weird thing:
When the inverter shows warning 12, he doesnt accept any commands from the terminals, and continues operating at the last frecuency. I have the signals "start", "auto start", and the analog signal (0-10) for the speed.
An example: I give the start signals and 10V for 100% speed. The inverter goes to 97% and stays there, showing warning 12.
If i reduce the analog signal to 5V, the inverter stays at 97% with his warning. Now i reduce the load, so that the warning goes away, and then the speed goes down to 50%.
If the inverter is in warning state with 97% speed, i can even remove the "start" and "auto start" signal, and nothing happens. If a reduce the load, then he goes up to 100%, taking the alarm away and then shuts off.

Had anyone experience with this problem and a posible solution? Like my load may vary, i cannot assure that the inverter never goes into torque limit, but i want him still to listen to my commands.


Best regards,
crawler009

I would find that kind of behavior unacceptable from a safety standpoint. Any vfd that does not stop when the Run command is removed should be red-tagged and taken out of service immediately (assuming two wire maintained start/stop control).

Hello DickDV,
there is also a safety stop for the frequency inverter,
if someone opens the door the motor stops.

That may be, crawler009 but if you would normally expect a stop and it doesn't occur, I find that a serious safety defect.

DickDV said:

That may be, crawler009 but if you would normally expect a stop and it doesn't occur, I find that a serious safety defect.

Click to expand...

You are right. And what never should be, that it becomes incontrolable during a warning state (except when it shuts down due to an error).

Hi Crawler!

Are we talking FC101 or FC102?

What is the firmware of the drive?

It does not look like it, but do you have Terminal 27 connected? This terminal is default "Coast Inverse" and I would expect this one to work in all conditions.

I do agree that a drive should react on its input no matter what, but the coast function of a Danfoss drive will have higher priority than the Start/Stop.

Best regards,

Michal_dk

Hello Michal_dk,

the Terminal 27 "Coast Inverse" is working fine (if i open the door). But dont want to trigger that signal, just to slow down (a little bit) the motor, its not like it should be. Im using Rockwell inverters (in most mashines) and they are working fine, even during warning state.

Its a 102, i just cant get firmware version right now (cause they are at a clients place). But its a new inverter, orderd like 3 months ago.


Best regards,
crawler009