Torque Control of G120

Hi Tech Team, thanks for the detailed reply. I think I am clear on what I need to do, however I am still not 100% certain on how to achieve it.

You mention that I should use p1503 "in the telegram" for the torque setpoint (and possibly p1501 to switch modes). But when i check these parameters to find which telegram address they correspond to they are both just set to '0'.

Presumably this means I need to parametise them myself with an address from the telegram, i.e. something from r2050? Or should I re-run the commissioning wizard with different settings?

Is there some documentation which explains the mapping of telegram 352, PZD-6/6 so I can better understand this aspect and select the most appropriate signals to use?

Finally, is there a way to view all the parameters currently set to use the telegram? This would be useful.

Many thanks

Chris

Technology Team

In these cases you have a real torque control, so if you have a sudden load drop your motor can accelerate up to maximum speed if the torque setpoint remains the same. A possibility to prevent this is using an overdriven speed controller. Here you are limiting the torque limitations of your drive according to your speed setpoint and you just send a speed setpoint which is a little bit higher than your real operating point. In this case the motor is operated on the torque limit all the time but it just speeds up to the slightly higher speed setpoint in case of a load drop.

 Hi, can you expand a little bit on how to do this second method? Do you simply monitor the torque in the PLC by reading the Actual Torque through the Status word, and adapt your speed setpoint? Or is there a cleaner way of doing this with drive parameterization?

Just this week I implemented (on an S120 drive) torque control while in speed control mode.

Siemens support suggested that approach, plus you can find several forum posts about it.

In my specific case, the torque limits (maximum / minimum) also have scaling factor parameters (on my S120, they were p1552 & p1554).

In the PLC, while in "torque" mode, adjust the scaling factors, which are basically 0-100% against the rated torque drive parameter (p2003 in S120).  So for 100% torque setpoint, I send 16384 which sets it to 100% of whatever is set in p2003.  If I wanted 200% torque setpoint, send 2x16384=32768.

I had 2 free words for sending to the drive via telegram so I just moved the torque setpoint scaling factor into those 2 free words, and in the drive, configured the telegram to move those 2 telegram words to the p1552 / p1554.

Otherwise, I would have used Sinamics library block SINA_PARA (or SINA_PARA_S twice) (available in TIA Portal).

You will have to find what parameters your G120 has available for the torque limits if you want to use this method.  Starter and the drive navigator worked great for me on the S120.

AutoGen_7036758

Technology Team

In these cases you have a real torque control, so if you have a sudden load drop your motor can accelerate up to maximum speed if the torque setpoint remains the same. A possibility to prevent this is using an overdriven speed controller. Here you are limiting the torque limitations of your drive according to your speed setpoint and you just send a speed setpoint which is a little bit higher than your real operating point. In this case the motor is operated on the torque limit all the time but it just speeds up to the slightly higher speed setpoint in case of a load drop.

 Hi, can you expand a little bit on how to do this second method? Do you simply monitor the torque in the PLC by reading the Actual Torque through the Status word, and adapt your speed setpoint? Or is there a cleaner way of doing this with drive parameterization?

0_Einstein, in your case it sounds like you were using a scaling factor to adjust an actual torque setpoint that you are sending to the drive? The concern I have about the direct torque setpoint is that the drive will run away if there is no load on it.

My G120 has the same parameters available, but I was curious about a method of torque control which would use SINA_SPEED block and therefore only telegram 1. The Technology Team's answer made me think that this was possible. I wrote some code to sort of chase the torque value that I'm looking for by altering the speed setpoint either up or down, so my motor kind of oscillates around a specific torque value but I'm not sure if this is what he meant when he said "overdriven speed control". 

Yes the scaling factors for max/min torque limits was what I used.  It allows speed control - preventing potential run-away conditions - while allowing a torque setpoint to be given.  That said, the speed setpoint needs to high enough that the generated torque will hit the torque limit before it hits the speed setpoint.

You can use SINA_PARA / SINA_PARA_S to send the torque limit scaling factors.  They are both 0-100% (positive values), so you basically send the same value to both, and then no matter what direction of rotating, you get the correct torque setpoint (limit). 

AutoGen_7036758

0_Einstein, in your case it sounds like you were using a scaling factor to adjust an actual torque setpoint that you are sending to the drive? The concern I have about the direct torque setpoint is that the drive will run away if there is no load on it.

My G120 has the same parameters available, but I was curious about a method of torque control which would use SINA_SPEED block and therefore only telegram 1. The Technology Team's answer made me think that this was possible. I wrote some code to sort of chase the torque value that I'm looking for by altering the speed setpoint either up or down, so my motor kind of oscillates around a specific torque value but I'm not sure if this is what he meant when he said "overdriven speed control". 

New question published by masoodanzar is split to a separate thread with the subject Commissioning of torque mode without PLC.

Best regards
Jen_Moderator