AB Powerflex 525 issues

[304sparky]

We have an Allen Bradley Powerflex 525 running a motor on a large saw. Roughly at the same depth of the bundle of metal beams that it cuts, the motor stops. All voltage is lost going to the motor. It takes about one minute to get a fault.

Is this normal to take that long to get a fault? It’s getting a F007 fault (OL fault). FLA on the motor is 12.2 amps, however running amps is typically around 5 amps. Motor OL is set to 7 amps. Current limit is set to 10 amps. However, even when current exceeds the current limit, it does not fault.

To my understanding, current limit is a hard number and once current reaches that number, it faults. Also to my understanding, motor OL is a softer number, once the number is reached, there is a time delay before a fault.

We have 4 identical saws and this is the only one we have this issue with.

Should it take one minute to show a fault?

Why does it not fault when the current limit is met?

 

[ptonsparky]

Have you tried resetting all parameters to defaults, then reentering?

 

[TwoBlocked]

There is probably an additional parameter you are missing for the current limit. One to activate the current limit, and one to set what the current limit is. Additionally, there may be a parameter to turn the stall-fault off, otherwise, the VFD may see that it is not coming up to command speed (because of the current limit) and decide the motor is stalling. (DAMHIK...)

How do you know the motor does not get any voltage during that one minute delay? Could it be the motor is just stalling?

 

[Jraef]

Current limit is not a fault. When you hit the current limit, it reduces the speed or changes the carrier frequency (or both as per your selection) to maintain the current limit. So by setting the OL current to 7A and the CL to 10A, the motor current is allowed to go to 142% of the OL current and the time it takes to trip is likely what is expected per the trip curve.

Why are you setting the OL current to be so much less than the motor FLA? Makes no sense.

 

[TwoBlocked]

...

Why are you setting the OL current to be so much less than the motor FLA? Makes no sense.

I was wondering the same thing, but I can think of reasons. Maybe to keep a shear pin from shearing, or to keep from the cuttings from becoming too hot.

 

[ptonsparky]

I was wondering the same thing, but I can think of reasons. Maybe to keep a shear pin from shearing, or to keep from the cuttings from becoming too hot.

I agree. I've monitored amperage via logic to prevent known issues that could occur well before motor FLA.

 

[Jraef]

I was wondering the same thing, but I can think of reasons. Maybe to keep a shear pin from shearing, or to keep from the cuttings from becoming too hot.

But I believe there is a shear pin-like feature anyway. I’m not sure how setting the sail so low would affect cutting temperature.