Cogging torque in coreless axial flux PMG (permanent magnet generator)

In summary: But coreless motors, lacking the core, have no preferred positions, so are much more easily rotated by external forces. So for a PM coreless motor any residual magnetism in the iron portions of the rotor and stator might produce a small but detectable torque.In summary, the conversation discusses a simulation of a coreless axial flux PMG, which has a significant cogging torque. The speaker is unsure where this torque comes from, as there is no core or slot in the stator. They request a drawing to better understand the design and question the possibility of induced currents causing the torque. The conversation also touches on the difference between static and transient simulations and the potential for residual magnetism to contribute to the cogging torque in a
  • #1
akbar94
1
0
Poster has been reminded to post more information when asking questions at the PF.
Hi to all. I am simulating a "core less axial flux PMG". This PMG has significant cogging torque. I don't know where this torque comes from because this is a core less generator therefor there is no slot in stator ( no reluctance variation).
 
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  • #2
Can you post a drawing so we have an idea of the design?
 
  • #3
akbar94 said:
I am simulating...

computer is quite happy to calculate anything
What have you instructed it to do ?
"Garbage in, Gospel out"

Indeed, as Tom.G asks, what does a coreless motor look like ?
akbar94 said:
no slot in stator (
Where do the stator wires go ?
 
  • #4
I don't know about these devices, but it seems to me that, if there's no core, the alternative source of reaction would have to be induced currents. So is there any possible current path even when no load is attached? I have in mind maybe some sort of delta connection rather than star connection of phases.

Edit. BTW for any like me not familiar with these simulations, perhaps you could explain a little what static and transient simulations are in this context.
 
  • #5
Actually I'm not too surprised by cogging torque. Likely due to the varying magnetic alignment between the rotor and stator. My experience with coreless motors is they are used when the rotational position must be stable without any applied power. Motors with a core, especially Permanent Magnet ones, have preferred positions where the rotor and stator will always settle due to the remnant magnetic field; they act almost like stepper motors with the power off.
 

Related to Cogging torque in coreless axial flux PMG (permanent magnet generator)

What is cogging torque in coreless axial flux PMG?

Cogging torque refers to the resistance or reluctance of a coreless axial flux permanent magnet generator (PMG) to rotate due to the interaction between the permanent magnets and the stator teeth. It is a type of electromagnetic torque that can affect the smoothness and efficiency of the generator's operation.

What causes cogging torque in coreless axial flux PMG?

Cogging torque is primarily caused by the interaction between the permanent magnets and the stator teeth. The arrangement and shape of the magnets and teeth can also contribute to the magnitude of cogging torque. Other factors such as eccentricity of the rotor and manufacturing imperfections can also play a role.

How does cogging torque affect the performance of a coreless axial flux PMG?

Cogging torque can cause fluctuations in the output voltage and current of the generator, leading to reduced efficiency and stability. It can also increase the mechanical stress on the generator's components, potentially leading to increased wear and tear.

What are some methods for reducing cogging torque in coreless axial flux PMG?

There are several methods for reducing cogging torque in coreless axial flux PMG, including using skewed magnets or stator teeth, optimizing the shape and arrangement of the magnets and teeth, and implementing advanced control algorithms to compensate for cogging torque. Other techniques such as adding damping materials or using magnetic bearings can also help reduce cogging torque.

Are there any drawbacks to reducing cogging torque in coreless axial flux PMG?

While reducing cogging torque can improve the performance of a coreless axial flux PMG, it can also increase the complexity and cost of the generator. Additionally, some methods for reducing cogging torque may also lead to a slight decrease in overall efficiency. Therefore, it is important to carefully consider the trade-offs and choose the most suitable method for each specific application.

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