VFD skipping accel rate intermittently 1

[thekman]

MGM (italian) Motor on Duff Norton Actuator
230v 3phase 50/60Hz
0.66kW (~1HP) @60Hz

Leeson 174276 1HP VFD
3ph 208vac input

Accel 2s (0-60Hz)
Decel 1s (60-30Hz)
Stop 0.1s (30Hz-0)

Been running this actuator in and out for a day & 1/2 w/o a problem. Was getting some data points and increased the accel time to 5.0 seconds, and when it retracted, the VFD started to ramp, then jumped to full speed (60Hz). I tried about 5 more times, and it did it 4 out of 5 times, the one time it didn't do it.
I reduced the accel to 1s and then 2s, and it still does it intermittently. The motor is suitable for inverter duty, is not hot, nor is the VFD. No error codes. I'm just running the actuator, no load.

Any ideas why my VFD is skipping the bulk of the accel ramp intermittently? Only on retract stroke, has not happened on extend stroke yet...


Thanks

 

[jraef]

Sounds like an electrical noise problem. How did you run the output conductors? How are you controlling the drive?


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[controlsdude]

Most vfds have multiple parameters for Accel and Decel. Try putting your Accel and decel values into all of them. Maybe the VFD uses these other parameters for some reason.

 

[itsmoked]

I have also been tricked by the huge number of parameters these days in drives. Often parameters supersede other parameters or regulate when they actually apply. I often have to work through every one of them them to find the 'ah hah!' one that is overriding the one of interest.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[controlsdude]

ITsmoked I was just on a startup and the firmware changed to where they had two paramaters for the FLA nameplate below.
Motor OL Current
Motor NP FLA
Of course I was operating from last years startup and did not change one and would not you know it that the other needs the same info. WTF? Why would some insane firmware designer make two parameters that do the same thing?

The mechanical checkout guy was looked over his stuff and said its my fault that the drive is overloading. Of course I look over my stuff since I know that Mr Murphy is right beside me. And stick the nameplate in the other parameter.

 

[jraef]

The reason some people enter different values like that is that they may want to have the OL current be lower than the mameplate current, because something else in the process can be damaged or indicated by a sustained increase in current. A classic example is a centrifugal pump system. The OL current can represent a maximum flow value but might be well below the motor nameplate current. So if a pipe break causes open channel flow, the current increases but maybe not over the motor nameplste FLC. Yet the drive takes it off line even though the motor isn't actually overloading yet, because that broken pipe means some other disaster is taking place. This could be done with a current trip/alarm setup as well, but using the motor OL instead gives you an I²t buffer to it.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[thekman]

Thanks for the replies....after another day or so of testing here and there, I did not experience it again while running at a 2.0s accel or less. I had to ship it to another facility for additional testing. We'll have personnel out there next week and I'll remind them to monitor operation for this.
JRAEF, I control it with discrete PLC outputs (dry relay op) which were only a few inches away. It was a really simple PLC program I wrote just to test the actuator, so I cannot rule out an out-of-sequence input that my program didn't handle well, but I didn't have a lot of time to troubleshoot, and it seemed fairly insignificant in relation to the test at hand. I wanted to be sure that there's no way the actuator motor could have had anything to do with it, I'd never seen one do that before, and never seen this motor (MGM) before.