ACS350 VFD Over Current Fault

[powersoff]

I have a blower fan Motor:20hp, 460, 22fla, 1.15sf, codeJ
DesA,ClassB.
The ABB ACS350 VFD controlling fan motor is occasionally faulting on a overcurrent.
It faults when automatically starting from a dead stop.In the fault history I can see the current at 51 amps. The drive is then powered down fault clears and motor restarts fine.
The acceleration time is 5 seconds.
Any ideas?
I have a second question is the current that is displayed in the HMI of the VFD dependent on parameters?
For example if I change the Nominal Motor Volts or current will the Current reading change on the HMI?

 

[DickDV]

First, the correct motor nameplate data must be entered properly in Group 99. Second, you must select Scalar Speed in Group 99 parameter 04.

After these things are done, the keypad display should read out the actual current to the motor.

Finally, remember that it takes extra current to provide the torque to accelerate the load. In your case, it may be that the 5 second accel is too fast causing the drive to hit the Overcurrent point and fault. I would start the drive and watch the displayed current to see what your accel current actually is and, if too high, widen the accel time out to 15 seconds or so and recheck the current.

If all of this seems in order, then you should report back to us the wire length of the motor leads and also whether the three phase power to the drive is grounded wye, floating delta, or some other configuration.

 

[jraef]

Also, what type of "blower fan" is it? If it is a squirrel cage blower, it must be started with the dampers closed, otherwise it will require a LOT of current to accelerate it from a stop. This is a VERY common error, people think that if the dampers are open, there is no load when in fact it is exactly the opposite.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[ozmosis]

and..as it is a fan, is the ACS350 trying to start a motor that is already spinning? If yes, and a function commonly known as Flying start has not been activated, it could now and then trip on overcurrent.
Is it tripping (the VFD stops on a fault) or is it going into alarm (the VFD issues a warning and the VFD might be going into current limit). If the VFD trips without going into current limit then this is usually indicative of a very fast current spike, maybe ground fault. If a warning appears and then a trip, it is often load related or, as DickDV points out, parameter setting related.

 

[jraef]

The more things we make drives capable of doing, the more things we make them capable of ceasing to do...

 

[DickDV]

Golly, jraef, isn't that the truth! Go anywhere-do everything is rapidly becoming go nowhere-do nothing!

Along the same lines, as an oldtimer like you in this business, I am more and more astonished at technicians and engineers literally forcing drives into fieldbus communications when the drives are all in the same box and all you are doing is start/stop and speed. I know fieldbus is powerful stuff but it instantly converts a system from easy troubleshooting to impossible troubleshooting.

Or, maybe I'm just getting old! Could be, I suppose!

 

[jraef]

I love the ones where they say they want to use a field bus to cut down on wiring. I ask them what they would connect, they say Start, Stop, Speed pot. I point out to them that this is going to take the exact same number of wires...


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[DickDV]

And they are surprised to hear that!

 

[powersoff]

Thanks for the replies.
The fan motor is designed to start against a closed damper. I have verified that the damper is closed when starting.

Would any ABB experts like to explain parameter 30 07(Allowed continuous motor load in percent of the nominal motor current).
Specifically if I set this to more then 100% could it potentially shorten the life of the motor.
Or is raising this value a reasonable solution?

Thanks

 

[DickDV]

Parameters 30.05 thru 30.09 are all used to construct the internal overload protection the drive performs for the motor. It is based upon the motor nameplate data entered in Group 99. That's why the Group 99 parameters must be an exact reproduction of the motor nameplate.

If the motor overload protection is activated, you will get a Motor Overtemp or Motor Overload Fault, not an Overcurrent Fault. So those parameters should be left at the defaults that the drive automatically calculates for you. If you have changed them, change Parameter 30.05 to off or not selected and then change it back to Fault and the drive will recalculate the others again.

Have you done any of the other things we requested. If so, what happened or what did you observe?

 

[powersoff]

I have verified Group 99.
-I did not change the from Vector to scalar though. Not sure of the ramifications of this.
-At low HZ <30 the current displayed reading is > then my Fluke 337 meter, as HZ increases the display and Fluke get close to matching.
-I have extended the accel time out to 10 seconds with the same result(drive occasionally faults on overcurrent on a start).
-Conductors(#8AWG THHN) length from VFD to Motor is roughly 10 feet.
-Incoming voltage is 494,495,494. Not sure if Delta or Wye.
-Motor is faulting when starting from a dead stop(not spinning when run command initiated).
This motor averages only couple starts a day ,it is a blower feed for a boiler. When it faults it turns into a crisis and whoever is closest to VFD clears fault and motor restarts.

 

[DickDV]

Running the drive in Vector Speed mode (Parameter 99.04) configures the drive as a closed loop speed regulator. This, when properly set up will provide precision speed control, much more precise than any fan can beneficially use. It also requires that the Group 23 P and I gains be set up to tune the speed loop and, further, it requires that a motor ID run be done in Parameter 99.10. If these have not been properly done, all sorts of troubles including the faulting you describe can occur. Plus, the speed regulation more than likely is worse than if operated in open loop Scalar or V/Hz mode.

I strongly suggest that you write down the parameters that have been changed from default and then change Parameter 99.04 to Scalar Frequency. You may need to re-enter the changed parameters if the mode change puts everything back to factory default.

I predict that you motor operation will improve and your fault problems will be history.

 

[powersoff]

Thanks for the reply DickDv.
This Drive was programmed by the supplier of the boiler. The tech shows up for startup everything runs fine. Now he's gone and troubleshooting a VFD fault that happens intermittently is not at the top his priority list.