Asymmetric Surface Magnet Rotor for Reluctance Torque Gain
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Solution Overview
Problem
Brushless motors with surface magnet rotors face limitations in maximizing output due to uniform magnetic flux distribution, leading to suboptimal reluctance torque generation.
Innovation Solution
The shaft member of the rotor is designed with varying cross-sectional areas and lengths in the d-axis and q-axis directions, facilitating differential magnetic flux passage, and incorporating bonded and sintered magnets to enhance magnetic force while reducing eddy current loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the shaft member has a uniform cross-sectional area in all directions, then the structure is simple and easy to manufacture, but the magnetic flux distribution is uniform which limits reluctance torque generation
Solution Approach 1:
The shaft member is designed with an asymmetric cross-sectional shape where the cross-sectional area in the d-axis direction differs from the cross-sectional area in the q-axis direction. This asymmetry creates non-uniform magnetic flux distribution in the air gap, enabling effective reluctance torque generation while maintaining structural simplicity for manufacturing
Solution Approach 2:
The shaft member incorporates localized variations in cross-sectional area at specific positions along the rotational axis. By making the cross-sectional area in the d-axis direction different from the q-axis direction at particular locations, the design creates localized magnetic flux concentration that enhances reluctance torque without requiring complete asymmetry throughout the entire shaft
2Loss of energy
If bonded magnets are used alone, then the eddy current loss is reduced, but the magnetic force is insufficient
Solution Approach 1:
The rotor combines both bonded magnets and sintered magnets in a hybrid configuration. The bonded magnets provide high resistance to eddy currents reducing energy loss, while the sintered magnets provide strong magnetic force. By merging these two types of magnets, the design achieves both low eddy current loss and high magnetic force output
Solution Approach 2:
The magnetic system uses a composite structure combining bonded magnets (with high electrical resistance properties) and sintered magnets (with high magnetic strength properties). This composite approach leverages the complementary strengths of different magnet materials to simultaneously reduce eddy current losses and maintain strong magnetic fields
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 design enhances reluctance torque generation, improving the motor's output by optimizing magnetic flux distribution and torque transmission, resulting in increased efficiency and performance.
Implementation Method 1
the ease of passage of magnetic flux can be made to be different in the d-axis direction and the q-axis direction in the shaft member. Thus, the output of the rotating machine can be improved using reluctance torque
Implementation Method 2
a magnet portion provided on an outer surface of the shaft member and forming alternating opposite magnetic poles along a rotational direction
Data Source
AI summary
A surface magnet rotor includes a shaft member extending along a rotational axis, and a magnet portion formed around the shaft member and forming opposite magnetic poles arranged along a circumferential direction. A cross-section of the shaft member includes an intermediate line extending from the rotational axis to a center point in the circumferential direction between a d-axis and a q-axis of the magnet portion. In the cross-section, a first cross-sectional area delimited by the d-axis and the intermediate line is different from a second cross-sectional area delimited by the q-axis and the intermediate line.