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

[akbar94]

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).

 

[Tom.G]

Can you post a drawing so we have an idea of the design?

 

[jim hardy]

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 ?

no slot in stator (

Where do the stator wires go ?

 

[Merlin3189]

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.

 

[Tom.G]

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.