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I need to fit speed control to two seperate Agitator Motors on a juice processing plant. The agitators need to be independantly controlled. The motors are 1.5kw The plant is controlled by a Allan Bradley SLC500. I have no analogue outputs, I have spare digital outputs. I need the agitators to speed up as the tank level rises and slow down as it reduces. I havent done this before and would appreciate advice on which Inverter to use and how best to achieve what i want. ?

Most VFDs have a set of preset speeds that you can control digitally. You would need sensors or float switches to sense several levels and write the logic to switch on a preset according to how many sensors are on. You wouldn't need to do too many levels before it would be worth it using a linear sensor and adding an analog input and output, but it can be done.

Regards
cww

Thanks.....
Well there is an analogue signal for tank level on both tanks. I could control digital outputs from PLC to the inverter using these. Any suggestion of a specific suitable inverter, to control 1.5 KW 3 Phase AC Motor. speed.

I like Yaskawa and Hitachi lately. You could also simply run the linear sensor input to the drive and use the digital outputs to let the PLC know what's going on. Most of the drives I've seen in that power range are well equipped for that type of thing. They even do PID control if needed.

Regards

cww

Hi Mickbeeee,
Did you read which PLC is best. Basically the same thing. Stock on hand in your counrty, hands on 24hr technicians, local experienced trades people, customer support and training options, ease of use (room for the neutral screened cables and good clamping systems) and last of all cost an extra $200 dollars now over a normal minimum operating life of 20,000 plus hours is nothing.

All modern drives have analogue inputs so if a PLC output is out of the question make that on/off/run return from PLC and transducer direct to the drive, or signal convert an existing transducer to do both jobs.

Best of luck Jason.

Try Milltronics uits with still wells. They will generate a 4-20 ma current, which I know will work with a PLC or with a Yaskawa VFD. Depending on the circumstance you may need and interface best provided by Red Lion Control of Ephrata, PA.

don
wdonpjr at gmail. com