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Permanent Magnet Setting
Posted Jun 21, 2017, 12:10 a.m. EDT Low-Frequency Electromagnetics, Materials, Parameters, Variables, & Functions Version 5.3 1 Reply
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Hi,
I want to simulate the magnetic field of a geometry of a magnetized Arnokrome 5 metal (a thin permanent
magnet alloy developed by Arnold Magnetic Technologies). In their datasheet, I only know the magnetic remanence (Br)=16kGauss and the coercivity (Hc)=20 Oersteds. Is it possible for me to do the simulation by using these two parameters? If so, what kind of settings shall I follow? Is it the case that I set "Magnetic Flux Conservation" and choose "BH curve" or "Remanent flux density" in the "Constitutive relation" list? Attached is the datasheet of the Arnokrome 5 that I found on website. Thanks for your help!
I want to simulate the magnetic field of a geometry of a magnetized Arnokrome 5 metal (a thin permanent
magnet alloy developed by Arnold Magnetic Technologies). In their datasheet, I only know the magnetic remanence (Br)=16kGauss and the coercivity (Hc)=20 Oersteds. Is it possible for me to do the simulation by using these two parameters? If so, what kind of settings shall I follow? Is it the case that I set "Magnetic Flux Conservation" and choose "BH curve" or "Remanent flux density" in the "Constitutive relation" list? Attached is the datasheet of the Arnokrome 5 that I found on website. Thanks for your help!
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1 Reply Last Post Jun 22, 2017, 3:32 a.m. EDT
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Posted:
7 years ago
Comsol is not very user friendly when it comes to defining permanent magnet materials and orientations. Materials with near linear demagnetisation curves (rare earth magnets in moderate temperature ranges) can be defined by a Br and relative permeability quite satisfactorily. Materials that have non-linear demagnetisation curves are more complex to set up and define.
Ideally, for a material like Anrokrome you would want a BH curve defined for the material, (it will be quite a non linear demagnetisation curve). The attached model is an Alnico 5 magnet (another highly non-linear BH curve material, though of higher coercivity and lower Br compared to Arnokrome).
The same principles can be employed for modelling your Arnokrome part. The attached Word file describes the general principle for modelling.
In the model attached, the magnet is always magnetised parallel to the global z axis. In this model, I rotate the part to show how the performance of a fixed size/shape magnet changes with magnetisation direction. (The permeance coefficient of the part changes under such circumstances. A magnet magnetised along its long physical axis will operate at a higher energy density than the same sized magnet that is magnetised through a shorter axis. Reason is that self demagnetisation becomes a significant effect in materials like Arnokrome and Alnico when magnetised through physically short axes).
The approach Comsol has in defining (non-linear) permanent magnets seems overly complex and not at all user friendly. It should be possible to define a magnet more easily, for example by defining the pole surfaces and BH curve, or by defining a magnetisation angle and BH curve. In my opinion it should not be necessary to hack around in the defining equations in order to model a non-linear permanent magnet. Furthermore, it would be great if we could define BH curves for a material at different temperatures.
I appreciate that the datasheet you provide does not have a BH curve, but you may be able to find one (or at least estimate one) in order to more accurately simulate the magnet.
Good luck, and if any Comsol employees feel like making a suggestion to simplify the procedure for defining non-linear permanent magnets, I am always keen to hear them!
Ideally, for a material like Anrokrome you would want a BH curve defined for the material, (it will be quite a non linear demagnetisation curve). The attached model is an Alnico 5 magnet (another highly non-linear BH curve material, though of higher coercivity and lower Br compared to Arnokrome).
The same principles can be employed for modelling your Arnokrome part. The attached Word file describes the general principle for modelling.
In the model attached, the magnet is always magnetised parallel to the global z axis. In this model, I rotate the part to show how the performance of a fixed size/shape magnet changes with magnetisation direction. (The permeance coefficient of the part changes under such circumstances. A magnet magnetised along its long physical axis will operate at a higher energy density than the same sized magnet that is magnetised through a shorter axis. Reason is that self demagnetisation becomes a significant effect in materials like Arnokrome and Alnico when magnetised through physically short axes).
The approach Comsol has in defining (non-linear) permanent magnets seems overly complex and not at all user friendly. It should be possible to define a magnet more easily, for example by defining the pole surfaces and BH curve, or by defining a magnetisation angle and BH curve. In my opinion it should not be necessary to hack around in the defining equations in order to model a non-linear permanent magnet. Furthermore, it would be great if we could define BH curves for a material at different temperatures.
I appreciate that the datasheet you provide does not have a BH curve, but you may be able to find one (or at least estimate one) in order to more accurately simulate the magnet.
Good luck, and if any Comsol employees feel like making a suggestion to simplify the procedure for defining non-linear permanent magnets, I am always keen to hear them!