VFD Torque Control

[LL631]

Hi,

I want to determine the break-away point of a brake driven by a motor. My plan is to gradually (or incrementally) increase motor torque from 0Nm until the brake gives way, I will use a torque sensor to measure the torque and the motor encoder to determine the point of break-away.

The question is what is the best way to control the motor to achieve this? Is it possible to achieve accurate motor torque control from 0rpm with closed loop vector control? Or would a better option be to use feedback from the torque sensor to achieve control?

Unfortunately I'm not very clued up on the subject so any pointers to useful information would also be appreciated.

Thanks.

 

[waross]

Save a lot of money and time.
Use a torque wrench and do it manually.
Probably more accurate also.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

I was just going to say the same thing.

Failing a torque wrench just us a mondo 6-point socket and long piece of pipe. Failing that, use a standard torque multiplier and a long piece of pipe.

The problem with a motor, besides totally thrashing it thermally, is that you'll likely have some serious torque cogging that will mislead you in the results. That's totally avoided with a wrench.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Compositepro]

You have to have a speed control loop, and this will have to be the primary control loop. Static friction is greater than dynamic friction. So when the brake starts to move, the resisting torque drops and speed will go out of control. For this reason, many attempts that I have seen to use torque control of motors do not work well.