Permanent Magnet Motor Arc Configuration Reduces Cogging Torque
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Solution Overview
Problem
Conventional permanent magnet motors experience issues with cogging torque and torque ripple, leading to vibrations and noise, and struggle to reduce these while maintaining motor torque.
Innovation Solution
A permanent magnet motor design featuring a stator with a ring-shaped yoke and teeth, and a rotor with permanent magnets arranged in a specific arc configuration, where the radii of curvature and their ratios are optimized to reduce cogging torque and torque ripple without significantly decreasing motor torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the permanent magnet thickness is fixed in zone Z1 to suppress decrease in motor output, then motor torque is maintained, but cogging torque and torque ripple cannot be reduced sufficiently due to abrupt thickness decrease in zones Z2 and Z3
Solution Approach 1:
The patent applies local quality by making the permanent magnet thickness non-uniform in a controlled manner across different zones. Specifically, the thickness is kept constant in zone Z1 (between radii R1 and R2) to maintain motor torque, while gradually decreasing in zones Z2 and Z3 (between radii R2-R3 and R3-R4) to reduce cogging torque and torque ripple. This localized variation in thickness allows each zone to serve its specific function.
Solution Approach 2:
The patent employs curved surfaces for the permanent magnet boundaries. The inside periphery is formed by a first arc with center of curvature O1 and radius R1, while the outside periphery is formed by a second arc with center of curvature O2 and radius R2. These curved surfaces create smooth transitions in the magnetic field distribution, helping to reduce cogging torque and torque ripple while maintaining motor torque.
2Object-generated harmful factors
If the permanent magnet thickness decreases toward end parts to reduce cogging torque, then cogging torque is reduced to some degree, but motor torque decreases significantly
Solution Approach 1:
The patent applies local quality by making the permanent magnet thickness non-uniform in a controlled manner across different zones. Specifically, the thickness is kept constant in zone Z1 (between radii R1 and R2) to maintain motor torque, while gradually decreasing in zones Z2 and Z3 (between radii R2-R3 and R3-R4) to reduce cogging torque and torque ripple. This localized variation in thickness allows each zone to serve its specific function.
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 optimized design effectively reduces cogging torque and torque ripple by up to 60% while maintaining motor torque, achieving a balance between noise reduction and efficiency.
Implementation Method 1
a magnetic attraction force generated between the stator and the rotor
Implementation Method 2
the air-gap magnetic flux density distribution generated between the permanent magnet constituting the rotor and the stator core constituting the stator
Data Source
AI summary
There is provided a permanent magnet motor capable of reducing cogging torque and torque ripple while suppressing a decrease in motor output. In a permanent magnet motor 1 including a rotor 3 in which a plurality of permanent magnets 5 are arranged in a ring shape as a magnetic field unit, the transverse cross section of the permanent magnet 5 has an inside periphery 51 formed by a first arc 511 having the center of curvature O1 and the radius of curvature R1, and an outside periphery 52 formed by a second arc 521 having the center of curvature O2 and the radius of curvature R2, a third arc 522 having the center of curvature O3 and the radius of curvature R3 and joined to one end of the second arc 521, and a fourth arc 523 having the center of curvature O4 and the radius of curvature R4 and joined to the other end of the second arc 521. The above-described centers of curvature are disposed at different positions.