Yokeless Stator Housing for Axial Flux Machine Cooling
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Solution Overview
Problem
Axial flux electrical machines with yokeless stators face challenges in mechanical stability and cooling capacity, particularly due to the absence of a yoke, which complicates accurate positioning of stator teeth and efficient heat dissipation without using internal water cooling.
Innovation Solution
A yokeless stator design featuring a housing with a circumferential portion and radially inward elongated portions made of non-ferromagnetic materials, providing structural support and enhanced cooling by evacuating heat from stator teeth to the circumference, while avoiding the use of internal water cooling and minimizing eddy currents through a laminated structure and electrically isolating filling material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a yokeless stator design is used to eliminate stator yoke losses, then efficiency is improved, but mechanical stability and positioning accuracy of stator teeth deteriorate
Solution Approach 1:
The stator is segmented into discrete teeth without a continuous yoke, with each tooth independently positioned and secured using retaining ribs and slots. This segmentation eliminates the stator yoke while maintaining structural integrity through localized support features.
Solution Approach 2:
The housing structure combines multiple functions: it provides mechanical support for the stator teeth, creates retaining ribs for positioning, forms slots for securing teeth, and establishes cooling channels. This merging of functions achieves both mechanical stability and efficient cooling without a traditional yoke.
2Ease of manufacture
If discrete stator teeth are used in a yokeless design, then manufacturing flexibility is improved, but mechanical rigidity and positioning accuracy worsen
Solution Approach 1:
The housing is pre-formed with integrated retaining ribs and slots during the molding process. These features are created beforehand to precisely guide and position the discrete stator teeth during assembly, ensuring accurate positioning without requiring complex post-assembly adjustments.
3Temperature
If internal water cooling channels are added to improve cooling capacity, then heat dissipation is improved, but device complexity increases
Solution Approach 1:
The housing structure is designed to integrate cooling channels directly into its walls, merging the cooling system with the structural component. This eliminates the need for separate cooling assemblies while providing efficient heat dissipation through the housing itself.
Solution Approach 2:
The housing serves dual purposes: it provides mechanical support for the stator teeth and simultaneously acts as a heat sink with integrated cooling channels. The structure serves itself by combining structural and thermal management functions in one component.
4Loss of energy
If non-ferromagnetic materials are used for the housing to reduce eddy currents, then energy losses are reduced, but mechanical strength may deteriorate
Solution Approach 1:
The housing uses composite construction with laminated non-ferromagnetic materials that provide both electrical isolation to reduce eddy currents and sufficient mechanical strength. The laminated structure combines electrical insulation properties with mechanical integrity.
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
The design achieves improved mechanical stability and cooling capacity, allowing for higher power density without internal water cooling, and reduces thermal resistance, enabling efficient heat transfer and operation without the complexity of internal cooling systems.
Implementation Method 1
the elongated portions having a proximal end which is mechanically connected to the circumferential portion and is in thermal contact with the circumferential portion, and having a distal portion or distal end which is physically located between electrical windings of adjacent stator teeth
Implementation Method 2
The circumferential portion of the housing is made of a first non-ferromagnetic material and the elongated portions are made of a second non-ferromagnetic material
Implementation Method 3
an electrically isolating filling material filling empty space within said circumferential portion between said plurality of stator teeth and said plurality of elongated portions
Data Source
AI summary
A yokeless stator for an axial flux machine, comprising a housing, the housing comprising a circumferential portion and a plurality of elongated portions extending radially inwards therefrom, and a plurality of discrete stator teeth arranged within the circumferential portion, each discrete stator tooth comprising a ferromagnetic material and an electrical winding; the housing further comprising an electrically isolating filling material filling empty space inside the housing. The circumferential portion of the housing is made of a first non-ferromagnetic material and the elongated portions are made of a second non-ferromagnetic material. The housing comprises a laminated structure, which comprises at least part of the plurality of inwardly directed elongated portions.