Torque regulation ?? MM440 Siemens

[userxyz]

Hi,

I have a frequency drive MM440.

I can set a maximum Torque, but I can make it variable with the analogue input, in that way you can choose the max torque.

When do u use Torque regulation, in what situation is that needed ?

 

[rdrast]

Torque regulation is typically used, well, when you want to control the torque delivered by a motor. This can be for a section that acts as a 'helper' to keep a web tight, or perhaps for an open (or closed) loop winder.

It boils down to some applications care about controlling speed, some care about controlling torque.

 

[Leadfoot]

One application that comes to mind real fast is a rotary table or top drive on a drilling rig. Different drill pipe size has different max torque that it can with stand before it twists in two.

By using torque limit you can effectivly reduce the max torque AKA horse power that is applied by the drive and motor. Thus preventing the potential power available from over powering the mechanical limits of the equipment you are using. The top drives can actually use the torque limits to break the connections loose and tighten the connections to specific levels.

Another place where torque regulation is used reqularly by industrial applications is winders. As you increase the diameter of the wound material, you want the torque or tension to remain constant. The speed of the winder must increase as the diameter grows larger and it takes more material to complete 1 wrap of the spool/drum. You want the torque to remain constant to insure even spacing and tight layers.

 

[rdrast]

The speed of the winder must increase as the diameter grows larger and it takes more material to complete 1 wrap of the spool/drum.

decrease.

 

[kamenges]

Both Leadfoot and rdrast gave examples that would work just as well running in velocity mode with a torque limit. In fact the case can be made that the winder application is better served operating in velocity mode with torque limit IF you modify the velocity reference with diameter. In that mode you don't have to worry about web break detection quite so much as the product roll won't 'run away' as quickly as it will in pure torque mode. The velocity controller will ultimately grab it. I may be wrong but I think Combo's question is, since you have the torque limit capability, why would you need pure torque control mode.

rdrast's example of a section helper is a good use for torque control if the two motors are rigidly coupled. In this case you prevent the torque controlled motor from running away since it can't come uncoupled from its partner and you don't have the problem of two velocity controllers fighting each other.

This is a personal opinion but I think high bandwidth positioning applications with a motion controller are easier to implement as a single loop controller with the drive operating in torque mode. You don't have to worry about tuning two loops.

Also, unless the drive does a REAL good job of babysitting the velocity loop integrator you can run into some issues if you need to change torque direction quickly as the intgral sum will need to wind down before your torque direction changes. This may be an issue with low tension center driven unwinds as you approach the core.

 

[Leadfoot]

decrease.

Arrgh. Thanks, we don't want to add to the problem.