Connecting an encoder to a VFD 1

[sham96]

Hello Everyone!

So we have this application that requires precise control of motor speed and torque. We were told that via the addition of an encoder , an ac drive can get speed feedback from the motor which can then be incorporated in the drive's control algorithm for closed-loop control.

Can somebody please enlighten us about how this can be achieved, for eg:
1. To what terminals of the VFD should the encoder be connected to?
2. The general parameters that will need to be set in the drive?

Very grateful for any help!

 

[itsmoked]

If you are actually talking about "motor speed and torque" then you do NOT need an encoder. You need only to engage the VFD's sensorless vector mode. You only need an encoder if you require the motor to provide full torque while stopped or to run down below 50 or so RPM.

What are you trying to do? What are you guys running with this VFD/motor? We can help you much more if you describe the process you're trying to run. We can likely speed your learning process up greatly instead of playing twenty questions in multiple fora.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[sham96]

Hello Sir!

So our application is this Sir:
We have a paper tuber machine and this machine is driven by a 5.5KW induction motor and another integrated unit which is for the printing and is driven by a 2.2KW motor. Our requirement is to synchronize both these motors so that both the tuber and printing units complete each rpm simultaneously.
We first attempted to do this by connecting the analog output of the tuber VFD to the analog input of printing VFD but perfect synchronization couldn't be achieved.
We now believe that using an encoder we can achieve perfect synchronization of the motor speeds. Could you please advise us how to do this since we really are trying hard to achieve this.

Thanks alot for your help Sir!

 

[BrianPetersen]

http://www.seweurodrive.com/produkt/movitrac-mc07b.htm

Requires a positioning module in order to be able to do it and it (supposedly) only works with their built-in encoder.

No idea how to do it otherwise or with hardware from other manufacturers (aside from using a servo motor, of course).

 

[sham96]

Sir is it possible to synchronize the motion of the above two motors using servo drives instead of VFD's? We haven't used servo drive technology before and are quite new to this. While researching I obtained this piece of information from a site :

"But did you know that an encoder can also act as an input signal to control and synchronize the motion of two or more motors?

Because the output from an encoder is a series of pulses, consisting of an A and B channel, these signals are very similar to the Step Pulse & Direction outputs that are commonly found on a PLC or indexer. With a few simple configuration steps, a stepper drive or servo drive can be configured to accept these encoder pulses as a command source."

Site Address :

https://www.applied-motion.com/news/2013/04/synchronized-motion-using-encoder-following

So is this actually feasible for motors with different power ratings?

 

[jraef]

It can be done with encoder feedback to VFDs capable of Flux Vector Control. Accuracy of FVC with an encoder is an order of 100 times better than SVC and positioning or coordination approaches servo-like precision using induction motors (albeit with more mass in the motor itself).

How you connect the encoder to the VFD is unique to each brand and model of VFD. Many require the addition of an encoder feedback card or module. If you have never done this before, you will want help. My suggestion is to find a good supplier with local support in your area and engage their support for the brand they sell. Nobody makes junk in this industry and survives, so the real differentiation usually come down to the support you can get from people.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[sham96]

Sir , thank you for sharing this valuable information with us. We weren't very familiar with the speed control methods available in an ac drive but this discussion has led us to a greater understanding of the topic and so very thankful for such a platform.

After studying the manual, we realized the ac drive that we have in possession doesn't support any encoder feedback control technique. The only control methods available are :
1. V/F Control
2. Vector control without PG
3. Torque control (Vector control without PG)

So we have made the decision to purchase a different model. Are there any models you would recommend Sir that would support our application?
And just another question that has been bugging us : When the motor shaft completes 180 degree rotation for example , is it possible for us to give a signal to the VFD via an encoder to pause operation?

Sincerely thankful for all the great feedback!

 

[BrianPetersen]

The SEW Eurodrive link that I provided earlier, is the one that I know of.

I second the recommendation to contact your local SEW Eurodrive distributor. At least in my area, SEW Eurodrive has good customer support. Call them! If you routinely deal with a different supplier (you haven't told us what you've got now), call them as well. Get the sales rep in, and show them your application and what you want to do.

 

[jraef]

Again, the best choice is usually the one that has the best local support for you. We don’t know where you are or what is available to you there. If you listed your available options we can likely give you feedback on our experiences (if any), but other than that many of us have vested interests in one brand or another and our bias will likely come though, so the value of these opinions must be tempered with that knowledge.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[sham96]

We are currently using Bedford AC drives from a Chinese supplier but we are planning to purchase ABB drives in the near future since we figured they have alot more built-in features that may suit our application.

I will definitely look into the SEW EuroDrive website and contact them for further details too Sir!

Thanks for the support and recommendations!

 

[jraef]

ABB and SEW are both very reputable companies that make good motors and drives capable of what you want to accomplish.

Never heard of Bedford... but it appears to be another of the many "generic" gray box Chinese drives meant to be as cheap as possible. the one I saw only offers V/Hz and SVC operating modes, it will not likely give you the performance you are looking for.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[sham96]

Noted Sir!
We will contact the technical support teams of both these companies for more information, Thank You