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Calculating of torque

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Hi

I have COMSOL 4.2a and I'm new in COMSOL. I'm simulating in AC/DC module Switched Reluctance Motor and I need to calculate torque of rotor and build plot of torque depending on angle of rotation. In user guide I found only equations how to calculate torque using Maxwell’s stress tensor and any example how to do it. Does someone have an example or user guide how to calculate torque.

Thank you in advance,
Artem

6 Replies Last Post 09.07.2017, 12:22 GMT-4

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Posted: 1 decade ago 02.05.2012, 05:43 GMT-4
Hi Artem

You need to add to your model tree a node "Force Calculation" under "Magnetic Fields" and select
the regions you want to compute the torque. Then after solving there is a
global variable for forces and torque.


In the hel look for
AC/DC Module > The Electric Field Interfaces > The Electrostatics Interface
which is applicable also in the magnetic case


Cheers

Jens
Hi Artem You need to add to your model tree a node "Force Calculation" under "Magnetic Fields" and select the regions you want to compute the torque. Then after solving there is a global variable for forces and torque. In the hel look for AC/DC Module > The Electric Field Interfaces > The Electrostatics Interface which is applicable also in the magnetic case Cheers Jens

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Posted: 1 decade ago 03.05.2012, 18:49 GMT-4
Hi

Thanks for the reply. I've calculated the torque, but when I do Global Evaluation I can choose Axial torque, Torque x, y, z components. So I always get ZERO for all torques, except torque z component, but I don't understand what is this torque mean and this torque much bigger than I calculated it analitically. As I understand z axis in 2d models mean length (depth) of the motor, but I needed the torque that lies on the x-y axes. Also z torque doesn't depend on lenght of the motor, I have length in Global Definitions, but I think I must somehow make torque depending on legth. I also tried to change Torque axis and Torque rotation point, but z torque changes when Torque rotation point much bigger than diameter of the rotor. How can I find a normal torque?

I attached my model.

Thank you in advance,
Artem
Hi Thanks for the reply. I've calculated the torque, but when I do Global Evaluation I can choose Axial torque, Torque x, y, z components. So I always get ZERO for all torques, except torque z component, but I don't understand what is this torque mean and this torque much bigger than I calculated it analitically. As I understand z axis in 2d models mean length (depth) of the motor, but I needed the torque that lies on the x-y axes. Also z torque doesn't depend on lenght of the motor, I have length in Global Definitions, but I think I must somehow make torque depending on legth. I also tried to change Torque axis and Torque rotation point, but z torque changes when Torque rotation point much bigger than diameter of the rotor. How can I find a normal torque? I attached my model. Thank you in advance, Artem


Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 04.05.2012, 02:57 GMT-4
Hi

that looks nice, the forces are high but that is also for a 1m long (deep in Z) device, so 12 N/cm is not that much, or ?

Check your depth in the main physics node.

A few comments: why not add the shaft to the magnetic iron domain and give it some mu_r > 1, also I often check my action/reaction forces hence also measure the force of the complementary parts (stator in your case).

The best force/torque values are obtaines when the part is fully surrounded by air (or the same material) I noticed only a few N difference if I add the air all around so its not really significant in your case. but dor the rotor, I would add the axis too if you add it to the magnetic domain.

Last thing, if you want to get a better mesh in tha thin air gap, add a circle with an inner boundary splitting the air in the middle of the gap and have some 4 nodes over the gap. You can then also use this boundary as a rotating one, in Geometry Assembly mode

Force/torque values are very sensitives to the mesh, I have often noticed that using "boundary mesh" can improve the values, to be tested carefully

Nice model

--
Good luck
Ivar
Hi that looks nice, the forces are high but that is also for a 1m long (deep in Z) device, so 12 N/cm is not that much, or ? Check your depth in the main physics node. A few comments: why not add the shaft to the magnetic iron domain and give it some mu_r > 1, also I often check my action/reaction forces hence also measure the force of the complementary parts (stator in your case). The best force/torque values are obtaines when the part is fully surrounded by air (or the same material) I noticed only a few N difference if I add the air all around so its not really significant in your case. but dor the rotor, I would add the axis too if you add it to the magnetic domain. Last thing, if you want to get a better mesh in tha thin air gap, add a circle with an inner boundary splitting the air in the middle of the gap and have some 4 nodes over the gap. You can then also use this boundary as a rotating one, in Geometry Assembly mode Force/torque values are very sensitives to the mesh, I have often noticed that using "boundary mesh" can improve the values, to be tested carefully Nice model -- Good luck Ivar

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Posted: 1 decade ago 04.05.2012, 13:02 GMT-4
Hi

Thank you very much Ivar. I've computed the torque and everything looks correct.

Cheers
Artem
Hi Thank you very much Ivar. I've computed the torque and everything looks correct. Cheers Artem

Maria-Sofia Pechlivanidoy

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Posted: 7 years ago 22.06.2017, 07:44 GMT-4
Hello Artem Polunin,
Your work is great!
I was wondering, if you can tell me how did you do your Tables?
How did you enter Column and Header to the Tables (Table 1 and Evaluation 2D)?
And how did you find the torque?
Hello Artem Polunin, Your work is great! I was wondering, if you can tell me how did you do your Tables? How did you enter Column and Header to the Tables (Table 1 and Evaluation 2D)? And how did you find the torque?

Maria-Sofia Pechlivanidoy

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Posted: 7 years ago 09.07.2017, 12:22 GMT-4
Hello Artem Polunin, can you attach your programm file with the torque?
Hello Artem Polunin, can you attach your programm file with the torque?

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