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Eccentricity in Rotating Electrical Machines
Posted 4 dic 2015, 13:44 GMT-5 Low-Frequency Electromagnetics, Geometry, Mesh Version 5.1 2 Replies
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I am a rotating electrical machine designer and I would like to study a machine under eccentricity fault. I aim to study a 2D geometry with the AC-DC package and in particular rotating machinery package. Is it possible to do such a study in comsol? My concerns are the following:
- usually for rotating machines the center of rotation is considered to be centered in the origin (0,0). As far as I know I always done like that in order to get reliable values of electromagnetic quantities, in particular about the electromagnetic torque. For eccentricity is it possible to prescribe rotation also around another axis getting fair values or is it better to change the stator position accordingly?
- in order to set up the mesh for time stepping simulation, how can I do? For healthy rotating machines (no accentricity) the mesh geometrical constraint is set by a pair formation along the airgap. However in this situation it does not work. Is there any other kind of method for dealing with an air-gap which is changing thickness at each time step?
- is it possible to simulate dynamic eccentricity? In this case the rotor will rotate around his axis which is displaced by the healthy one, and at the same time it will be whirling with a certain vrotational velocity around the healthy axis. In this case the axis position along which the rotor is really rotating is varying his coordinates at each time step. Is it possible by any chance to set up a simulation like this one?
Do you have any kind of advice?
If you have any advice or suggestion I will be really grateful.
Sincerely,
Nicola
Hello Nicola Chiodetto
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Have you seen this Rotation axis base point in RMM module, rax, ray, normally we keep it zero, if you give some other points (constants), then it will model static eccentricity and if you give a time varying point, in a synchronous machine its the frequency/pole pair, it will model dynamic eccentricity. Just remember than select the force calculation NOT touching the domain with the boundary of stator. you may make 4 layers of airgap (which i do normally). In this way you dont need to change the mesh at every time step.
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Vic
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yes eccentricity is possible, I have done this several time.
You must take care that the circle that you use for the continuity pair has the same
centre as your rotation. You cannot use pole symmetry any more, you must model half of the machine or even all of it.
For me it worked fine to use the same mesh on the stator and on the rotor side
of the pair (by using the copy edge method)
One way of making the centre of rotation move is to combine rmm with the moving
mesh physics. This can be difficult if you have two movements on the rotor, but you can put
the rotation on the stator and the movement of the axis on the rotor. (But I admit this
takes some time to implement)
Regards
Jens