motor runs backwards a sec??

[leitmotif]

Why is it a problem
if the motor
AFTER stopping
is driven backwards for only a second?

Have seen this on pumps of course does not seem to harm a thing.
Dan Bentler

 

[silva.foxx]

Have you tried swapping over the two drives or the two motors you have mentioned?
Would this be easy to do?

You also said that when you toggled the relevant bits the motor performed correctly - so are all inputs signalling correctly?

Has the system worked correctly since maintenance carried out their run?

 

[CaseyK]

I will admit that I haven't read the whole thread.

After it runs forward, is it electrically running backward, or could it be backwash causing in the pump turning the de-energized motor backward?

regards.....casey

I try to look for the obvious, and this is the simplest logic I could come up with...

 

[DickDV]

Set your drive display to show output frequency. Then, run your system and start or stop in a typical scenario that will produce reverse rotation. Watch the drive frequency display and the forward/reverse indicator to see if the drive is telling the motor to roll backward.

If the drive is not telling the motor to roll back, then you can be sure the load on the motor is pushing it backward.

If the drive is telling the motor to roll back, you have a control issue with the drive. There are lots of possibilities but I would first try to determine if any forward/reverse inputs are switching unexpectedly. If not, I would look at speed loop tuning (only if the drive is operating sensorless or flux vector). The P and I gains can be way too low or way too high allowing this kind of behavior.

If none of this gives you any useful data, come back and we will help further.

 

[plcnewbie]

Ok guys thanks for all the help and here is the update. And remember I am plcnewbie for this reason I guess.

After pulling up the drive in Drive Exec and covering my tracks again I decided to force the motor on again and control it with the switch mounted by it. I ran it and bam!! The overcurrent section went to yellow and hit 6Amps. The only thing I knew it had to be then was something hanging it up right?

Yes, After thorough inspection it turns out the plastic belt was replaced the prior week on day shift and we had not run the line til today so I had no idea the fool that did it ran the estop cable right up against the belt and it got wedged in hence the springing back motion that appeared to be reverse rotation. That was not all there were also a few other parts that were caught up.

To make a long story short I rerouted the estop pull and rehung the belt and am now up and running halfbutt til the conveyor fools show up tomorrow to redo the job right.

Thanks again for the replies and help. I knew I could count on this site. I learned a great deal more on the conveyor system today cause of this so not at all a bad thing. And perhaps am one step closer to changing my name to something else....

 

[Eric Nelson]

Who worked this bucket last?

Yes, After thorough inspection it turns out the plastic belt was replaced the prior week on day shift and we had not run the line til today so I had no idea the fool that did it ran the estop cable right up against the belt and it got wedged in hence the springing back motion that appeared to be reverse rotation. That was not all there were also a few other parts that were caught up.

For many years, a guy by the name of Granville King wrote great tech articles for 'Four Wheeler' magazine. A few guys here might remember him. He also wrote a humorous book called "The Jeep Bible", which was sort of like a 'Dummy's Guide to Jeep Repair'. Enjoyable to read, but also full of useful information. I will always remember one of his quotes, because it holds true with all machinery. He said to always think "Who worked this bucket last?", meaning "What was the last change made before it stopped working?". 9 out of 10 times, that's the culprit... :nodi:



-Eric