motor control

[cabber]

Hi,

I have a dc motor that normally rotates in one direction for steel coil winding. I have noticed that after threading the coil onto the mandrel (beginning to wind the coil), the shaft first rotates in the opposite direction (slightly) and then begins to rotate correctly. I use an Avtron M785 tach (1200 PPR). Is there anything in particular that I should look into to resolve the 'reversing' issue? I am thinking that it is a tach issue.

Thanks

 

[panelman]

or even some of the real type

 

[jbartos]

Suggestions to cabber (Electrical) Dec 3, 2003 marked ///\\okay the problem resides when a reel in the beginning of the process switches over from being speed regulated to being voltage regulated. the switch causes tension to drop 65%, which means less control between the entry reel and the exit reel. the exit reel, during this state, backs up due to the movement of the entry reel.
///Please, clarify how this back-up works.\\ we don't use brakes, during the transition, and the solution will be software based.
///Please, clarify if there happens to be any dynamic braking over the software solution.\\\

 

[RadarRay]

What do you mean by going from speed control to voltage control. If this is a drive, I would have expected you to go from speed control (i.e. jog or thread) to Torque control. You do not mention any tension sensing device, so that is how I would expect this machine to run. And why do you list a generator in your data if it is a DC drive??

Also you mentioned to Cabber that it always backs up when first started. Is this only when the web is attached or even when you are in speed mode with no web and starting from zero?

Besides all the other possiblilities mentioned, the problem could be a web handling/drive problem. If in fact you go from speed to torque, if the tension build up is high between the coiler and the bridle at stall, you could be switching to a torque value which is less than the existing force on the web. Thus the web pulls the coil back slightly at the moment of changeover.

You should pay particular attention to the current being supplied to the motor at the instant of changeover. Does it really go reverse or is it just dropping to a lower level.