Positioning with PowerFlex Inverter

Good morning Sirs,

My bosses would like to perform a positioning, to actuate a lift, with a SEW asynchronous motor and a PF (until now a PF 40P). A Rockwell technician came here and said we'd have to use a special program for the PF a use a 4-wire encoder to perform this positioning. It doesn't have to be that precision, but it can't lose the point every time I use it, or after some actions it will be out of my work point.

I was thinking of using the encoder on my PLC (ML1400) and send some signals to it, such as "reduce speed" and brake commands. When my encoder performs "n" pulses I'll send a reduce signal and after more "n" pulses a brake signal.

My point is: the PF with my asynchronous SEW motor can perform that positioning the way I said, with my ML1400 sending those commands? The set of this lift isn't too heavy, at least I think.


Thanks in advance.

How accurate does this need to be?
How fast does it move?
How much time do you have to make the move?

These will determine whether you can simply issue digital commands out of the ML1400 or if you need a more accurate method.

Your biggest challenge will be "torque proving", or making sure the drive has control of the lift before you release the brake. That may be where the custom program for the PF comes in.

Keith

You can control the speed via 0 to 10v with the ml1400 built in a/o and use the d/o to command run fwd/rev/stop

The problem is my ML1400 doesn't have the analog I/Os and my bosses won't buy that kind of PLC or expansions. What I have is a 1766-L32BXB, nothing more than that.

I asked the engineer and he said the lift will be actuated around 60 times per minute, or less than that.

About the accurate he said there is a clearance o 20mm, what correspond approximately to 45º.

The torque we already tested with the inverter in continuous rotation, but not using the brake... we'll have to test it. The torque is around 12Nm.

Is this a stacking table of some type? If you need to make a full up/down stroke every second you won't do it with a PF40. If you just need to drop 20mm once every second you should be able to do that using a PF40 with discrete interface.

I would personally use an analog sensor of some type for the lift position. You could use an A-quad-B encoder but you will need to reference it when your plc is powered on. A multi-turn absolute encoder would work also but you have no way to get that into the plc.

If your boss won't buy you the appropriate components for the job you may just want to tell HIM to make it work.

Keith