Halbach Array Motor with Segmented Magnetization for Torque Ripple Suppression
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Solution Overview
Problem
Existing electromagnetic devices, particularly rotary electrical machines, face issues with torque ripple, heat dissipation, and high back electromotive force at high rotation speeds due to the complexity of the dual Halbach array field system, leading to vibration, noise, and reduced operational efficiency.
Innovation Solution
The electromagnetic device employs a field system with permanent magnets arrayed in a specific direction, changing magnetization by steps of an angle computed from the electric angle, and uses air-core coils with a stator made of magnetic material to suppress torque ripple and enhance heat dissipation, while maintaining high output torque at high rotation speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a dual Halbach array field system is employed to effectively utilize magnetic fields and obtain high output torque, then the magnetic field utilization is improved, but torque ripple is generated due to large harmonic components in the flux density distribution
Solution Approach 1:
The patent employs an asymmetric magnet arrangement where permanent magnets are positioned only on the rotor side rather than symmetrically on both stator and rotor. This asymmetric configuration modifies the flux density distribution to reduce harmonic components while maintaining effective magnetic field utilization, thereby suppressing torque ripple while preserving high output torque capability
Solution Approach 2:
The patent changes the magnetization directions of permanent magnets by specific angles (e.g., 45°, 135°, 225°, 315°) relative to the radial direction, rather than using the standard 90° step Halbach array. This parameter modification alters the flux density waveform to reduce harmonic content, particularly the 5th order harmonic, thereby suppressing torque ripple while maintaining strong magnetic field interaction
2Loss of energy
If a dual Halbach array field system is employed to obtain high output torque with high efficiency at low rotation speeds, then the efficiency is improved, but a large back electromotive force is generated at high rotation speeds
Solution Approach 1:
The patent modifies the magnetization angle parameters of the permanent magnets from the standard Halbach array configuration to specific angles (45°, 135°, 225°, 315°). This parameter change optimizes the flux density distribution to reduce harmonic components, which in turn reduces the back electromotive force at high rotation speeds while maintaining efficient energy conversion at low speeds
3Power
If armature coils are disposed inside the rotor of a double cylinder structure, then the dual Halbach array field system can be implemented, but heat dissipation becomes difficult
Solution Approach 1:
The patent extracts the armature coils from the rotor and relocates them to the stator. This separation removes the heat generation source from the rotating assembly, allowing for much more effective heat dissipation in the stationary stator structure while the rotor can be optimized for high-speed rotation without thermal constraints
Solution Approach 2:
The patent segments the electromagnetic device into distinct functional components: the field system (permanent magnets) remains on the rotor for high-speed operation, while the armature coils are placed on the stator for effective heat dissipation. This segmentation allows each component to be optimized for its specific function without compromising the other
4Power
If a double cylinder structure with outer rotor and inner rotor is adopted to dispose armature coils, then the dual Halbach array field system can be implemented, but the rotor structure becomes complicated
Solution Approach 1:
The patent extracts the armature coils from the rotor structure entirely and relocates them to the stator. This eliminates the need for the complex double cylinder rotor structure, allowing the rotor to be simplified to a single cylinder containing only the permanent magnets, thereby significantly reducing structural complexity while maintaining the dual Halbach array field system functionality
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 effectively suppresses torque ripple, cogging torque, and back electromotive force, improving the stability and efficiency of the electromagnetic device by allowing for better heat dissipation and increased output at high rotation speeds.
Implementation Method 1
a field system including plural permanent magnets arrayed in a prescribed direction such that magnetization directions of the permanent magnets are changed in sequence by steps of an angle computed by dividing one cycle's worth of electric angle of current in the coils by a number of divisions
Implementation Method 2
an armature provided with three-phase coils... One out of the armature or the field system moves relative to the other out of the armature or the field system in the permanent magnet array direction
Data Source
AI summary
In an electric motor, three-phase coils are provided to an armature disposed between an outside field system and an inside field system, and Halbach arrays are employed in the outside field system and the inside field system. Each of the Halbach arrays is divided by a number of divisions that is any number computed by adding two to a multiple of three. Permanent magnets are arrayed such that their magnetization directions are changed in sequence by steps of an angle computed by dividing one cycle's worth of electric angle by the number of divisions. Torque ripple is thereby suppressed in the electric motor.