Soft Magnetic Composite Baseplate for Eddy Current Reduction
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Solution Overview
Problem
Permanent magnet machines, particularly fractional slot concentrated winding machines, experience high eddy current losses leading to reduced efficiency and increased rotor temperature, which can result in premature power de-rating or magnet demagnetization, with existing solutions like magnet segmentation and laminated baseplates being costly or limited to large machines.
Innovation Solution
A permanent magnet module using a baseplate made of soft magnetic composite material, segmented into portions aligned parallel to the circumferential direction of the machine, combined with a non-magnetic cover to minimize airgap and reduce eddy current losses, while maintaining mechanical integrity and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If magnet segmentation is used to reduce eddy current losses, then eddy current losses are reduced, but manufacturing cost and complexity increase
Solution Approach 1:
The baseplate is segmented into multiple portions arranged circumferentially around the rotor, with each portion having a different circumferential extension than the permanent magnet it supports. This segmentation disrupts eddy current paths while maintaining structural integrity and simplifying manufacturing compared to segmenting the magnets themselves.
Solution Approach 2:
The baseplate portions are designed with non-uniform circumferential extensions, creating local variations in the magnetic circuit that specifically target eddy current reduction in high-loss regions while maintaining optimal magnetic coupling where needed.
2Loss of energy
If laminated baseplates are used to reduce eddy current losses, then eddy current losses are reduced, but manufacturing cost increases significantly
Solution Approach 1:
The baseplate is constructed from composite material composed of electrically insulating granulated material mixed with binder material, providing eddy current reduction equivalent to laminated structures but at lower manufacturing cost and without the complexity of layer-by-layer lamination processes.
Solution Approach 2:
The electrical properties of the baseplate material are modified by incorporating insulating granulated material, changing the electrical conductivity parameter to reduce eddy currents while maintaining mechanical strength and manufacturability.
3Length of moving object
If a metallic cover is used to reduce mechanical airgap, then mechanical airgap is reduced, but magnetic airgap increases due to flux leakage
Solution Approach 1:
A non-magnetic intermediate material is used between the permanent magnet and the metallic cover, allowing the cover to provide mechanical support and reduce mechanical airgap while the non-magnetic material prevents magnetic flux leakage, thereby maintaining magnetic coupling efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Significantly reduces eddy current losses, enhancing the efficiency of permanent magnet machines and increasing annual energy production in wind turbines by effectively managing rotor losses without significant cost increases.
Implementation Method 1
the high level of sub-harmonic in the airgap flux density leads to large amounts of eddy current losses in the rotor (magnet and baseplate and rotor house)
Implementation Method 2
the metallic airgap between stator and rotor is reduced by the thickness of the cover. The stainless-steel cover is normally not magnetically conductive, so that it does not reduce the magnetic airgap or the torque due to flux leakage
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
A permanent magnet module (101, 102, 103, 104) for a permanent magnet machine (10) comprises at least a permanent magnet (200) fixed to a baseplate (301, 302, 303) comprising a soft magnetic composite material.