Offset Coil Layout for Permanent Magnet Motor Torque Ripple
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Solution Overview
Problem
Synchronous motors with permanent magnet arrays, such as the yokeless and segmented armature motor (YASA), often experience significant torque ripple and torque cogging, leading to motor noise, wear, and reduced efficiency.
Innovation Solution
The use of offset and overlapping stator coils in an electric motor design with opposed magnet arrays, along with a slotted core ring and division of windings between the core ring sides, helps to reduce torque ripple and cogging while preserving high torque density and magnetic path lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If standard permanent magnet arrays are used in synchronous motors, then high torque density is achieved, but significant torque ripple and torque cogging occur causing motor noise and wear
Solution Approach 1:
The stator coil assembly is segmented into two separate coil arrays (first and second coil arrays), each positioned on opposite sides of the permanent magnet arrays. This segmentation allows independent optimization of each coil array to reduce torque ripple and cogging while maintaining high torque density.
Solution Approach 2:
The two coil arrays are positioned asymmetrically with different angular offsets relative to the permanent magnet arrays. The first coil array has a first angular offset and the second coil array has a second angular offset, creating an asymmetric configuration that balances magnetic forces and reduces torque ripple and cogging effects.
2Object-generated harmful factors
If magnets are skewed or offset to reduce torque ripple, then torque ripple and cogging are reduced, but magnetic path length increases and torque density decreases
Solution Approach 1:
Instead of skewing magnets in the axial direction (adding length), the solution introduces a new dimensional approach by positioning coil arrays on both sides of the permanent magnets with different angular offsets. This angular offsetting in the circumferential dimension achieves torque ripple reduction without extending the magnetic path length axially.
3Object-generated harmful factors
If rotor displacement is used to reduce torque cogging, then cogging torque is reduced, but alignment precision and manufacturing complexity increase
Solution Approach 1:
The solution creates a mirrored configuration with two coil arrays positioned on opposite sides of the permanent magnet arrays. Each coil array is a copy of the other but with different angular offsets, allowing the system to achieve cogging reduction through the combined magnetic fields without requiring precise rotor displacement or complex manufacturing tolerances.
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 effectively reduces torque ripple and cogging torque by up to 87% compared to similar motors, enhancing motor efficiency and reducing noise and wear, while maintaining high torque density and compatibility with standard magnet structures.
Implementation Method 1
a coil assembly (mounted for relative rotation with the permanent magnet assembly) positioned between the first magnet array and second magnet array, the coil assembly having a first coil array of circumferentially spaced coils facing the first magnet array and a second coil array of circumferentially spaced coils facing the second magnet array
Implementation Method 2
a permanent magnet assembly having a first magnet array of circumferentially spaced permanent magnets in opposition to a second magnet array of circumferentially spaced permanent magnets
Data Source
AI summary
An electric motor having opposed permanent magnet arrays employs overlapping offset coils positioned between the arrays to reduce torque ripple and cogging torque.