Electric Machine Crosspiece with Magnetic Anisotropy
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Solution Overview
Problem
Electric machines face inefficiencies due to high magnetic flux leakage, which increases the magnetic resistance and reduces the efficiency of the machine, especially in high-power motors, as the magnetic field lines are forced from the tooth region into adjacent slots with higher magnetic resistance.
Innovation Solution
The active part of the electric machine, such as the stator or rotor, incorporates a crosspiece with ferromagnetic properties and magnetic anisotropy, where the easy magnetization axis is oriented parallel or at an angle less than 25° to the coil axis, and the slot wall is made of anisotropic material, while the crosspiece core is isotropic soft-magnetic, reducing leakage flux and improving flux conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the magnetic flux density in the crosspiece is increased to improve the flux collecting function, then the magnetic conductivity is improved, but the leakage flux increases due to field displacement into adjacent slots
Solution Approach 1:
The crosspiece is divided into two regions with different magnetic properties: the slot wall region uses anisotropic magnetic material to suppress leakage flux, while the core region uses isotropic soft-magnetic material to maintain high magnetic conductivity for flux collection. This local differentiation allows each region to optimize its function without compromising the other.
Solution Approach 2:
The crosspiece employs a composite structure combining anisotropic magnetic material (for slot walls) and isotropic soft-magnetic material (for core). This composite approach integrates the advantages of both material types: the anisotropic material's ability to restrict flux in specific directions reduces leakage, while the isotropic material's high permeability ensures efficient flux conduction through the core.
2Ease of manufacture
If conventional isotropic soft-magnetic material is used in the entire crosspiece, then the manufacturing is simple, but the leakage flux is high due to field displacement into slots
Solution Approach 1:
The crosspiece is divided into two regions with different magnetic properties: the slot wall region uses anisotropic magnetic material to suppress leakage flux, while the core region uses isotropic soft-magnetic material to maintain high magnetic conductivity for flux collection. This local differentiation allows each region to optimize its function without compromising the other.
Solution Approach 2:
The crosspiece employs a composite structure combining anisotropic magnetic material (for slot walls) and isotropic soft-magnetic material (for core). This composite approach integrates the advantages of both material types: the anisotropic material's ability to restrict flux in specific directions reduces leakage, while the isotropic material's high permeability ensures efficient flux conduction through the core.
3Loss of energy
If the easy magnetization axis is oriented parallel to the coil axis, then the leakage flux is reduced, but the manufacturing precision requirement increases for aligning the anisotropic material
Solution Approach 1:
The patent specifies that the easy magnetization axis should be oriented at an angle of less than 25° (preferably less than 15°) with respect to the coil axis. This parameter definition provides a clear manufacturing target that balances performance optimization with manufacturability, allowing for reasonable tolerances while still achieving significant leakage flux reduction.
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
This configuration significantly reduces leakage flux, enhancing the efficiency of electric machines by minimizing the magnetic conductivity issues in high-power motors and improving electromagnetic compatibility, allowing for better flux distribution and reduced power demand.
Implementation Method 1
the crosspiece has a material which has, at least in certain areas, magnetic anisotropy with an easy magnetization axis and a hard magnetization axis
Implementation Method 2
the crosspiece has ferromagnetic, in particular soft-magnetic, properties
Implementation Method 3
A magnetic flux is conducted through the coils by means of the crosspiece
Implementation Method 4
the slot wall is made of anisotropic material
Data Source
AI summary
An active part for an electric machine can be configured as a stator or a rotor and includes at least two slots for arranging an electric coil winding of an electric coil. Arranged between the two slots is a crosspiece which is made of a material for conducting a magnetic flux through the electric coil which surrounds the crosspiece. The material has, at least in one area, magnetic anisotropy with an easy magnetization axis, which is oriented parallel or at least at an angle of less than 25° with respect to a coil axis of the coil, and a hard magnetization axis. The crosspiece is configured to form for each of the slots a slot wall which contains the material. The crosspiece includes a core which is made of an isotropic soft-magnetic material.