Using a servo as a brake

[Riff 1]

So, I'm currently attending school, and one of my teachers wants to use a NC282 and a Accurax G5 Servo drive and motor to use as a brake. Using a motor that is controlled by a frequency inverter to drive the servo motor, and using the servo as a brake to measure torque.. is this possible? Kurt

[Sergei Troizky 26]

Do you mean the servo to apply controlled counter-torque in order to measure the AC motor torque? The CJ1W-NCx8x is made for positioning and does not have torque control mode, but only torque limit during positioning. So, I would say not impossible, but not as straightforward as with native torque control mode. Also, not sure CJ1W-NC282 exists. Probably CJ1W-NC281? Edited 12 Jan 2015 by Sergei Troizky

[ParaffinPower 13]

The Nc card can in fact do torque control. You need to use a CJ2H though. The CJ2M is, as Sergei says, position only. Pp

[Riff 1]

NC281 yeah. Sparky, do you have any pdf or url that I can read up on this?

[Sergei Troizky 26]

Riff, the features of the CJ1W-NC281 (and any other NC as far as I know) are the properties of the module itself, and are the same whether it is installed on CJ2H or CJ2M, or even CJ1 or CP1. For direct torque control, you need another module, which probably will require another servodrive and/or network. EDIT: This was incorrect. Edited 13 Jan 2015 by Sergei Troizky

[ParaffinPower 13]

Sergei. I've used it. From manual W487-E1-14: The Synchronous Data Link function is available when the CJ1W-NC?82 PCU (unit version1.3 or later) is used in conjunction with a CJ2 series CJ2H-CPU?? CPU Unit (unit version 1.4or later).In addition, when used in conjunction with a G5-series R88D-KN??-ECT Servo Drive (version2.0 or later), the PCU can provide speed control (CSV)/torque control (CST) based on controlcommands updated in the Synchronous Data Link Area.The PCU also supports the Electric Shaft function (CSP) that performs synchronized axis controlbased on the multiplication factor configured for any axis in the same unit.

[Sergei Troizky 26]

Thanks. Will know.

[Sergei Troizky 26]

Where have you got this from? The latest one I've found is W487-E1-05: "Appendix 9: Torque control... Supported in unit version 1.3 or later for CJ1W-NC_82." Note: this is not applicable to NC281. Edited 13 Jan 2015 by Sergei Troizky

[Mendon Systems 22]

I think that the -14 must be a typo. Where did you find the -05 version?? The newest one I have found is -04 dated 2010.

[Sergei Troizky 26]

http://www.fa.omron.com.cn/data_pdf/mnu/w487-e1-05_cj1w-nc281_481_881.pdf?id=2643

[Mendon Systems 22]

Got it!! Thanks!! The strange thing is the the -05 version is 4 pages longer than the -04 but the PDF file size is less than half. They must have done something different????

[Michael Walsh 268]

I am not sure how this would work. If you put the servo drive in torque mode, it will apply whatever torque you command, no more, no less (unless there is not enough load for the commanded torque). You could time how long it takes to stop if a specific torque is applied, but the torque output would be what was commanded. I would also be concerned about regeneration. I would think that you would need a regeneration resistor. Perhaps I am not understanding what you are trying to do. If I am incorrect in my assumptions, please explain. It might be possible to slowly ramp up your torque command to see when the AC Drive stops. If that is your plan, that might work. By the way, "Sparky" is not his name, it is ParaffinPower. I believe Sparky is related to the number of posts, or perhaps it is a title that you can modify in your account settings.

[Riff 1]

It sounds like your assumptions are correct :) If you think of the servo motor as coasting (spelled right?), with the async motor driving it and the servo slowly braking to measure torque. I haven't been able to find anything about it in manuals or by googling it, so I really can't see how it could be done. And I see the name thing also :P I need to slow down when I read ;) Kurt

[Michael Walsh 268]

People do the name thing all the time. I just thought that I would point it out.... Good luck.

[Riff 1]

I think I'll let the teacher figure this one out by himself :P It's not an assignment, but they have just aquired servo's and never used one before, so I'm asked to help, since I use servo's on some of my projects. Thank you for all the reply's guys :) Kurt