Axial Flux-Switching Machine Structure for High Torque Density
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Solution Overview
Problem
Existing electrical machines suffer from low torque or force density and poor low-speed efficiency, leading to the need for mechanical systems like gearboxes, which introduce additional losses and maintenance costs.
Innovation Solution
The development of a rotating electrical machine with a rotor and stator comprising multiple discs with magnetic flux predominantly in the axial direction, utilizing magnetic gearing to reduce winding resistance and increase airgap area per unit volume, thereby enhancing torque or force density and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional electrical machine design is used, then the machine structure is simple, but the torque or force density is low
Solution Approach 1:
The machine is divided into multiple discs (stator discs and rotor discs) arranged axially, with each disc contributing to the total torque or force. This segmentation allows the machine to achieve high torque density by accumulating force from multiple airgaps while maintaining a modular structure that is manageable in complexity
Solution Approach 2:
The invention transitions from traditional radial flux machines to axial flux machines, utilizing the axial dimension for magnetic flux path. Multiple discs are arranged along the axial direction, creating multiple airgaps in series, which increases the total active airgap area per unit volume and thereby increases torque or force density
2Productivity
If traditional electrical machine design is used, then the machine operates at high speed, but the low speed efficiency is poor
Solution Approach 1:
The invention changes key parameters including using multiple discs to increase the total airgap area, employing magnetic gearing to reduce winding resistance, and optimizing the flux switching mechanism. These parameter changes enable the machine to maintain high efficiency at low speeds by reducing resistive losses and improving the power factor
3Force
If mechanical systems like gear boxes are used to increase torque, then the torque or force density increases, but additional losses and maintenance requirements increase
Solution Approach 1:
The invention replaces mechanical torque multiplication systems (gear boxes, hydraulic systems) with an electrical solution based on axial flux disc machines. By arranging multiple discs axially and using magnetic gearing, the machine achieves high torque density directly, eliminating the need for mechanical conversion systems and their associated losses and maintenance requirements
4Loss of energy
If modulated pole machines with magnetic gearing are used, then the winding resistance is reduced, but the leakage magnetic flux increases
Solution Approach 1:
The machine is segmented into multiple discs with interleaved stator and rotor discs, creating multiple airgaps. This segmentation allows the useful magnetic flux to be distributed across multiple airgaps while the leakage flux, which does not contribute to torque, is minimized by the careful design of magnetic circuits and the use of magnetic shielding in certain embodiments
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 proposed solution achieves significantly higher torque or force density and efficiency, especially at low speeds, while maintaining a decent power factor, thus overcoming the limitations of traditional electrical machines.
Implementation Method 1
The winding loop encloses magnetic flux from n magnetic poles of the same polarity where n is larger than 2
Implementation Method 2
utilizing magnetic gearing to reduce winding resistance and increase airgap area per unit volume
Implementation Method 3
The two end cap discs are mechanically connected by a stiff mechanical structure which mechanically transfers more than 15% of the axial magnetic attraction force acting on one of the two end cap discs to the other of the two end cap discs
Data Source
AI summary
A rotating electrical machine operating by switching of magnetic flux comprises a rotor (10), a stator (20) and a winding, having at least two phase windings. The electrical machine comprises at least 5 discs being either rotor discs (12) or stator discs (22), having a magnetic flux in the axial direction. The stator discs and rotor discs are interleaved with each other via airgaps along an axial direction. The winding loop encloses magnetic flux from n>2 magnetic poles, where the winding loop length is shorter than 2*n*d, where d is the airgap width distance. The two end cap discs are mechanically connected by a stiff mechanical structure (80B) which mechanically transfers apart of the axial magnetic attraction force acting on one of the two end cap discs to the other of two end cap discs.