DC Motor Drifting/Speed Issue

[catfaneng]

I have a 1HP DC Motor driving a fleeter that reverses direction upon command. I am using a speed reference from another dc drive to control the speed of the fleeter (through discrete adapter board). Both of these are driven with an older model AB 1395 Drive. With a 0 speed reference coming into the fleeter drive I am commanding the fleeter motor to be at 0 speed but the motor will drift. I can remove the speed reference cable at the drive and it will still drift. I can adjust the offsets in the drive and eliminate the drifting but that causes the motor to run faster in one direction than the other. All of this just started after replacing the discrete adapter board. I tried another board - same thing. Is there anyway this could be a motor issue and not a drive issue?

 

[itsmoked]

What are you using to read back the position?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[catfaneng]

We are using a prox to count revolutions on the worm gear that is driven by the fleeter motor. We are then using a relay to switch polarity to reverse the motor.

 

[itsmoked]

I have not done a lot of this but it sounds to me like your drive is losing it. Since disconnection from the other drive still leaves the drift I think your drive is having some component fail.

I don't know how hard it would be, but a test would be to swap the drives. If the drift follows the drive you have it.

I can think of no mechanism thru which the motor could cause this. And your prox as described shouldn't be doing it either.

Older drives relied on lots of analog circuitry that can start shifting as the components age.

The fact that it started after the I/O board change is either pure coincidence or you static zapped the drive during the work. This kind of problem is typical of 'zapped' analog circuitry.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[BearB]

We had a AB1395 with similar issues although the feedback was a tach. Replaced the Control Board and so far have not seen the problem repeat. Did not reload parameters, swap E2 chips.

 

[catfaneng]

Thanks, I will try changing out the main control board. Maybe the board was zapped during instalation of the discrete board, as itsmoked stated.