I am facing problem with synchronisation of two heavy motors (430 kw). One runs as master and the other as slave. They are not mechnically coupled but use sylsen for synchronisation.

We are in process of replacing the slsyn with digital encoders and a micro-controller read and process the position feedback and to generate error signal accordingly.

It has been seen that while running with loads the torque of two blades connected to each motors gets disturbed and the the position gets disturbed and system trips. Will our method of replacing selsyn with digital encoders and feeding the position error signal to drive circuit work succesfully.

Expert comments, advices and experiences solicited. Thanks.

 

You may have more luck posting this question on http://www.eng-tips.com, its more inclined towards heavy electronics and power

 

Not a conventional problem but I've done similar where it was absolutely necessary that two big motors maintained the same position relative to each other all of the time to within a small tolerance.

By cutting blades I presume that yr application is continuous - ie the machine doesn`t do cycles running up to speed and then stopping at a position? You do have variable speed drives - right? Are they AC or DC?

I would say that the two drives should not be master-slave but two master drives (ie each with its own speed loop) each with digital encoder for optimum speed response and the controller sends a speed signal offset + or - to each drive according to which motor is in front/behind. Synchronising of start, speed ref is obviously very important and the second drive could have a trq input from the first drive to add to the speed loop output to help a bit there.
With master-slave configuration of un-coupled motors the speed of each one is ultimately dependant upon its load. If the slave takes a little more load it will slow down relative to the master motor and the master drive won`t know about it
I would like to know more about the drives you have though - probably they don`t have inputs for selsyns? Also, yr controller probably won`t have the possibility of connecting the selsyns either?
What is the controller?

Using encoders for the position correction will be OK but the incremental counts will wrap-around in the controller and you need to be careful at this moment when subtracting one count from the other to produce yr error. Basically, a bit of inteligent programming here.
Contact me at [email protected] if you want some more help. I like meaty applications!

Dandare

 

You can read about T300 Angular Synchronisation module of Siemens usen with Siemens Masterdrive
AC Drives. This module is designed for such applications.

 

> You can read about T300 Angular Synchronisation module of Siemens usen with Siemens Masterdrive
> AC Drives. This module is designed for such applications.
Siemens have T400 Angular synchronisation module that will work on siemens ac or dc drives. eg, Master Drive or DC master. You do not have to worry about any position differences between two motors. This module with CFC software takes care of it.

 

Dear Sri Rishikumar,

I am looking for indian make selsyn for oparation of liquid resistance of a motor by a pair of selsyns. I shall be obliged should you help me in giving addresses thereof.

thanks in advance,
p rathore