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## Synchronous machine (torque)

Posted Jun 10, 2013, 5:23 AM EDT AC/DC & Electromagnetics Version 4.3 30 Replies

I am new to COMSOL. I am tryng to build three phase synchrnous machine model. I have applied three phase voltage to the machine but unable to generate torque in a machine, I do not waht is wrong with my model.

Any help will be highly appreciated. Please find model attached.

Thanks

Madhu

Please find attachment now. Look forward to your reply.

Best

Madhu

Attachments:

I would like to help you, but it is from the mph-file not clear what you

want to do. A few points

+ you can put all in one physics node "rmm"

+ make sure that the current in the two branches of one coil flow in

opposite direction

+ why is the variable definition disabled?

The file as it is does not even run. If you have fixed these problem

post the file again, then we can take another look.

Regards

Jens

I want to do analysis of forces acting on the rotor in static mode and also want to see the change in inductances of the machine due to rotor saliency. I n short I want to do magnetic circuit analysis of machine.

I have attached model with some modification. I have used mf physics because I want to do time dependent analysis. I have applied three phase voltages to the stator and excited rotor circuit by constant DC voltage. I want to see the electromagnetic forces and torque generated in the machine but I am unable to do so, it always shows an error at the end of the simulation that unable to evaluate forces.

Any help from you side will be appreciated. You can do changes in my model if you want to do.

Best,

Madhu

Attachments:

I get around 570 kNm.

My corrections:

+ the two branches of each coil must be fed with currents (or voltages in

your case) in opposite directions!!

+ I have selected only the rotor for forces calculation of the rotor.

+ You have decided to use mf, so there is not real rotation and therefore

transient simualtion does not make sense. I replaced it with a parametric stationary

analyis. The parameter "t" now is a pseudo, that only turns the load angle

of the stator. This already gives you a good answer for the torque of the machine.

Have fun with it

Jens

Attachments:

Thank you very much for your help-I highly appreciate. Iam unable to open the model you have attaced in you reply, I am using COMSOL 4.3, I suppose you are using some higher version, so cannot open the model in older version i.e 4.3 . Could you please do it in a 4.3, if you have excess to it or possible for you.

Thanks once again for your help!

Best

Madhu

If you cannot do it in any other version, could you please share snap shots of modification you did. I am new to COMSOL and do not know how to apply curent in opposite direction, | shall be very thankful to you if you add the snapshots of all the changes you did- It would become easier for me to understand.

I shall be thankful to you.

Best,

Madhu

but I am using 4.3 and no later version is out, as far as I know

The precise version is COMSOL 4.3.2.152.

The major changes to you file are those that I listed in my

initial response.

If I find time this weak I may check with earlier versions, but

I cannot promise when.

Regards

Jens

I look forward to your reply. I have posted another question, could you please see that and let me know the solution.

Thanks,

Madhu

then tell me which version are you using? I cannot upgrade or downgrade to other versions.

Did you implement my suggestions?

To the other post: you still have the currents in the two branches of one coil flowing

in the same direction!!!!

Also the domains you want to use for the "Prescribed Rotational Velocity" must

be a circle.

In the geometry the last step must be "Form an assembly" with two objects: one for the

stator one for the rotor.

You first step should be to work through the tutorial name "generator 2d" .

Regards

Jens

I am using version 4.3. I donot know how to apply current in opposite direction. Could you please eloborate it bit further.

I shall be thankful.

If possible, could you please share snapshots of changes you made, I do not know which version you are using, I am unable to open it in COMSOL 4.3 . Let me know.

Thanks

If you have an ealier version upgrading is a good idea anyway.

Opposite current:

you need to make two nodes with "multicoil" (or "single coil" wharever applies), one for

each branch. You set +Iop to one an -Iop to the other.

Regards

Jens

Thank you very much. I have did all the modifications whatever you said. I have attached the fresh model. But when I apply stator and rotor excitation plus velocity to rotor simultaneously, I am getting some wierd result, when I see the animation.In attached model. Could you please see my model and tell me where I am doing mistake.

I shall be thankful.

Best,

Madhu

Attachments:

Thanks

your permenant magnets all all pointing inwards, if you invert every

second you will see satisfactory results.

Regards

Jens

oh! yes I figured out that mistake and rectified it but still unable to see satisfactorily results. When I run simulation and see the animation, it seems my rotor body is rotating but the field seems stationary, it should rotate with the rotor. I donot know what is wrong with my model. Let me know, if you know solution of this problem.

Thanks!

Madhu

that is only a visualisation issue. E.g. goto Data Sets/Solution 1 and set Frame to Spatial.

Jens

Thank you very much for your help, it makes sense now and yes it was visualization problem.

Jens, I am extending my model to 24 slot stator now, could you please tell me how can I apply three phase voltage to my stator as there are now so many positive and negative of each phase, do i need to use integrate function, if yes could you please tell how this actually works.

Thanks,

Madhu

this depends on the wiring scheme that you want to apply to your

machine. I cannot help from the distance. The will be six types of coil

domains, three phase have an up and a down direction each. That is

about all for a general answer the rest depends on what your machine

actually looks like.

Regards

Jens

Let me figure out my machine structure and than I will do winding accordingly. Jens, I am stuck in finding mutual and self inductances of machine, could you please help me in finding inductances.

Thanks

Madhu

Please see my attached model. I want to measure the inductances of the machine (self and mutual). I donot know how to go next to measure inductances, any help will be highly appreciated. My task is: lets say if I just excite phase-A, I want to see how much of phase A flux is linking with other two phase i.e ultimately mutual inductances between phases.

I look forward to your help.

Thanks!

Attachments:

at this point I would use dq-transformation (=Park's transformation).

Then self inductances are in direct and quadrature axis and the mutual

inductance between the two.

Is that what you need?

Regards

Jens

I do not want to do dq transformation. Lets say my model is acting as a transformer i.e stator and rotor both are stationary, I want to calculate mutual flux liknage between phases and self as well. Lets say I excite only phase-A and than I want to calculate how much of phase-A flux is linking with other two phases (i.e Laa, Lab, Lac etc) . I know once I know flux linkage, I can easily find inductances by dividing it with current. I have attached model- in which I have tried to calculate flux likage by method defined in paper attached. Please have a look at my model and tell me am I doing write job or not,

I shall be very thankful to you.

Best,

Madhu

Attachments:

Thanks

the flux variable is the correct flux computation.

Jens

Thanks for the help. I have extended my model to 24 slot stator and it seems fine. Now, I want to calculate induced voltage in rotor circuit due to rotating stator flux. Could you please help me - how can I find induced voltage in rotor circuit due to stator flux. Please refer model attached.

I shall be very thankful.

Thanks,

Madhu

Attachments:

mf.VCoil_7-mf.VCoil_8

to evaluate the voltages.

I think your domains in the definition of +Ib are wrong.

Regards

Jens

Yes, I had a mistake in b+ domain - I have corrected that one but I am getting convergence error -unable to run the simulation : I am getting following error.

Failed to find consistent initial values.

Last time step is not converged.

Could you please help me how can I deal with this error.

Thanks!

Madhu

I suggest that you run a stationary simulation first, to make sure that

the inital state is appropiate. When you start rotating, also it is a good

idea to ramp the speed from 0 and not to start with full speed directly.

Regards

Jens

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