HI guys new to this site, I just starting working with plcs and have a question. I have two AC Torque motors (advantage is these ac motors provide a constant torque at stall without burning out the motor). I need to control the torque automatically with a plc (the work with tension sensors to provide the proper amount of torque to keep constant tension in the spooling fiber). In order to control the motors you need to vary only the voltage supply; i.e. variable frequency drives will not work. Someone mentioned an analogue triac output but I have not seen any sort of variable voltage ddrive that can connect to a plc. Does anyone have any solutions. I have to use these AC torque motors, I think servo motors are way beyond my budget.

Okay

There are two fiber spools each with a mounted ac torque motor. The spooling fiber is being spooling onto a spooling fiber for a particular length. The fiber is then de-spooled from both spools and cut in as its being pulled from both spools. The machine is only in motion about a third of the time but a certain amount of tension needs to be applied even in this stall mode in order to prevent tangles (its a wavelength shifting fiber and is very expensive). Hence the reason for ac torque motors to supply torque to create this tension. That same level of tension needs to be regulated while the machine is in motion (via tension sensor inputs to the plc) Essential the program logic will ideally take tension level inputs and send a vary ac output voltage to the motors (PID) for continuous tension control. thanks again. Oriental Motors did not have any suggestions besides triacs, but I believe those vary the frequency.

tenbaum

 

I'd say that you have an economic problem here. Expensive product, but no money to control it. You are starting out with a very difficult circumstance.

A decent multi-axis servo controller would be your best chance for success.

Galil make some nice controller/drive combos that support low cost brush style DC servo motors. I'd start there...

 

This may be a bit of extra work, but a variac with a homemade actuator control would do the job.

 

The variac brushes would probably wear quickly. Phase control might work, check with the folk that do linear heater control, Watlow, etc. Phase control doesn't change the frequency. If the motors are reasonably small this could be done analog with amplifiers with excitation controlled by a dc in attenuator. With larger motors this could be done with fixed pwm to a bridge with control of the supply voltage to set torque. There are many way this can be done, not too many are going to be off the shelf. The pwm idea is very close to what an AC servo amp might do. You could even do this with a saturable reactor, which might actually be the easiest way. Or if you can open your mind a little, driving common motors and varying the frequency very slightly with a vfd in a torque loop will do what you want with stuff you can buy.

Regards
cww

 

I have seen similar applications to this, and the correct AC drive will work. I have used the http://www.ssddrives.com 690 series drive (Parker/Compumotor SSD Drives division) for applications just like this. They have a new series 890 that looks very nice that I have not yet used. All of their drives have pre-canned functions that make what you are doing very very easy. Call them and get some info. You should replace the torque motor with a standard vector motor, which can hold full torque at zero speed (again use the right AC drive), and it is an off the shelf motor and not expensive like the torque motors are.

BW

 

Selectronics makes a great dancer-controller for spooling -- it's what you need. Took me years to find this. Originally made for the fabric industry, so spooling fibre is essentially the same thing.

http://www.selectronic.com/DCD1.htm and others.

Great stuff, good prices.

Happy customer.

Jeff Kreines
Kinetta