Torque limiting with VFD

As mentioned, there are many levels of drives, and many levels of torque accuracy.

Closed Loop Vector would be the tightest, but far more accurate than required for this application.

ABB's 800 series are good. Control Techniques' M700 is even better (higher resolution and faster update times). But again, more than needed.

The CT M200 in RFC (Rotor Flux Control) is more than adequate. Just leave AI1 pointed to speed Reference, and set AI2 to Motoring Torque Limit (4.005). Works like a charm. 10 turn pots give good enough resolution. The built-in PLC can be used with input from limit switches and pushbuttons to automate the rest of the functions...

Thank you guys for the detailed information.
I get it now. We have to look for a drive with open loop flux vector control.
It will operate in speed control mode but with torque limit monitoring with both references set by pots.
CT M200 looks really interesting with Codesys built-in PLC but I don't think that we will be able to find it. Schneider, ABB and maybe Yaskawa, Invertek are the available options for us.
Something like ATV61 or ATV71.
https://www.schneider-electric.com/en/faqs/FA226014/

@Gene Bond
So what do you do when torque limit is reached?
Do you stop, move the gate back and wait for some time before going forward again?

It seems that theoretically it can be done even with ATV320 but I'm not sure that it can work as good as on ATV61 or ATV71.

Why use a PLC this all can be done in a VFD look at the A1000 or the QA800 drives
either one will do what you need. don't use any pot's they can change values with temperature change enter the values in the digital key pad I would still use a sensor keep the gate from contacting the cows set up time to reverse nd restart when the gate gets to the cows. and a said before be sure to ground everything I would select 240vac if available. less potential use an isolation transformer to supply the power.

Levi G said:

Where could I find these regulations or specs on how to ground for stray voltages in Dairies, like how to ground water troughs,steel corrals/fencing or rebar in concrete.



How does a person check for stray voltage?

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There is a full section in the UK wiring regulations BS7671. However, I'm not sure they will be applicable to your country.

The idea is to 'crowd' the cows, so the drive continues the pressure on the group. Just a stalled motor no biggie. Of course use a motor rated for 1000:1 speed range.

I would think continually bumping them and backing off would just **** them off

The PLC functions are for limit switch logic for start, stop, reverse, override, etc. Occasionally a bull can get in there, and all bets are off. Pushing a bull is a different adventure!

GaryS said:

... don't use any pot's they can change values with temperature change enter the values in the digital key pad....

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The mechanical stiction and friction vary considerably with temperature as well, so it's easier to twiddle the pots than mash the keys...