Permanent Magnet Motor Stator Core Cogging Torque Reduction
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Solution Overview
Problem
Conventional permanent magnet rotary motors face limitations in reducing cogging torque while maintaining torque levels and achieving balanced inductance in exciting winding sections.
Innovation Solution
The design incorporates a stator core with alternately disposed first and second type connecting portions, featuring through-holes of varying lengths and angles, which counteract cogging torque waves and balance inductance by strategically arranging the phases and lengths of these holes to minimize torque reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional stator cores with uniform connecting portions are used, then manufacturing is simplified, but cogging torque cannot be sufficiently reduced
Solution Approach 1:
The stator core's connecting portions are segmented into two distinct types (first type and second type) with different through-hole configurations. This segmentation allows each type to be optimized for specific functions: one type prioritizes manufacturing ease while the other targets cogging torque reduction, resolving the contradiction between manufacturing simplicity and harmful factor reduction.
Solution Approach 2:
Different local regions of the stator core (different connecting portions) are given different qualities through the two types of through-holes. The first type connecting portions have through-holes configured for easy manufacturing, while the second type have through-holes specifically designed to reduce cogging torque. This local differentiation allows simultaneous optimization of both manufacturing ease and cogging torque reduction.
2Object-generated harmful factors
If through-holes are added to connecting portions to reduce cogging torque, then cogging torque is reduced, but inductance balance in exciting winding sections deteriorates
Solution Approach 1:
The two types of connecting portions introduce controlled asymmetry in the stator core structure. By strategically placing different through-hole configurations in specific circumferential positions, the design creates asymmetric magnetic paths that reduce cogging torque while the overall symmetric arrangement of the two types maintains inductance balance across the three-phase winding sections.
Solution Approach 2:
The first and second type connecting portions are arranged in a periodic alternating pattern around the stator core. This periodic arrangement ensures that the inductance variations caused by different through-hole types are distributed uniformly across all phases, maintaining inductance balance while continuously reducing cogging torque through the periodic interruption of magnetic flux paths.
3Object-generated harmful factors
If pole columns are disposed at unequal intervals to reduce cogging torque, then cogging torque is reduced, but device complexity increases
Solution Approach 1:
Instead of using asymmetric pole column spacing, the invention introduces asymmetry through the connecting portions between uniformly spaced pole columns. The first and second type connecting portions have different through-hole configurations, creating asymmetric magnetic properties in otherwise symmetric pole column arrangements. This approach reduces cogging torque while maintaining the simplicity of uniform pole column spacing.
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 approach effectively reduces cogging torque without significantly decreasing torque levels and balances inductance in the exciting winding sections, enhancing motor performance.
Implementation Method 1
a plurality of holes are formed discontinuously along an axial direction in its connecting portions and are opened both inwardly in a radial direction and toward a slot between two adjacent pole columns. The plurality of holes are formed in order to prevent leakage of magnetic flux among the magnetic poles.
Implementation Method 2
permanent magnet rotary motors including a rotor having permanent-magnet magnetic pole sections composed of permanent magnets and a stator having a stator core and exciting winding sections
Data Source
AI summary
The present invention provides a permanent magnet rotary motor in which cogging torque can be reduced without largely reducing the torque. When an angle formed between two virtual lines respectively connecting a center of a rotary shaft and both ends of a first type connecting portion 21A is defined as a first angle θ1 and an angle formed between two virtual lines connecting the center of the rotary shaft and both ends of a second type connecting portion 21B is defined as a second angle θ2, the relationship between the first angle θ1 and the second angle θ2 is θ1>θ2. A through-hole H1 is formed in the first type connecting portion 21A, which extends from a center position of the first type connecting portion 21A as viewed in an axial direction of the rotary shaft toward both sides in the axial direction. A through-hole H2 is formed in the second type connecting portion 21B, which extends from a center position of the second type connecting portion 21B as viewed in the axial direction toward both sides in the axial direction. The length, in a circumferential direction, of the through-hole H2 formed in the first type connecting portion 21A is longer than the length, in the circumferential direction, of the through-hole H2 formed in the second type connecting portion 21B. The length, in the axial direction, of the through-hole H1 formed in the first type connecting portion 21A is shorter than a length, in the axial direction, of the through-hole H2 formed in the second type connecting portion 21B.