Hi,
We have a cable reeling drum which is driven by a 7Nm Torque Motor. The torque is changed by adding or cutting out resistances. This has been in use for the past 30 years. Now we have planned to modernise. Can an AC Motor and a VFD be used to replace the torque motor arrangement?

Ron

 

Ron,

I would use a VFD in vector mode (use it with an inverter duty motor with differential quadrature encoder feedback). This will give you the best speed control when performing torque control (torque limiting). The torque limit could be set via a potentiometer, preset values and a selector switch, or even a comms bus. I would suggest using some type of torque regulated speed following mode for this application. This mode will keep the motor from running away if it loses the cable or load, etc. Most decent drives can do this. Consider a Unidrive SP from Emerson/CT if you want to do it closed loop. You should talk too an applications engineer for motor/drive sizing. Emerson or their distributors should be able to help with that as well... or again any decent drive company of your liking.

Brandon