Stator Tooth Design for Rotating Electrical Machine Torque Ripple
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional rotating electrical machines experience torque ripple and cogging torque due to differences in magnetic resistance between same-phase and different-phase teeth, particularly the sixth-order component of cogging torque when no current is applied.
Innovation Solution
The design includes a rotor and stator with teeth of varying circumferential widths, where the width of the second tooth's magnetic path is smaller than the first tooth's, and the tip ends of the second tooth are chamfered to reduce magnetic flux density, making the magnetic resistance of both paths similar, thereby reducing torque ripple and cogging torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tip ends on the radially inner side of the different-phase teeth are chambered to equalize magnetic resistance, then torque ripple is reduced, but cogging torque (especially sixth-order component) is generated due to shape difference between same-phase and different-phase teeth
Solution Approach 1:
The invention applies different treatments to different parts of the teeth: the tip ends (opposing portions) of both same-phase and different-phase teeth are given the same shape to reduce cogging torque, while the circumferential widths of the magnetic path portions are adjusted differently to equalize magnetic resistance and reduce torque ripple. This local differentiation resolves the contradiction by addressing each issue at its appropriate location.
Solution Approach 2:
The tooth structure is divided into two functional segments: the tip end (opposing portion) that faces the rotor core and the magnetic path portion that forms the flux path. By independently designing these segments with different characteristics (same shape at tip ends, different circumferential widths in magnetic path), the invention simultaneously addresses both torque ripple and cogging torque issues.
2Reliability
If the circumferential width of the magnetic path portion of the second tooth is reduced to equalize magnetic resistance, then torque ripple is reduced, but the tooth structure becomes asymmetric causing cogging torque
Solution Approach 1:
The invention creates local quality differences in specific portions of the teeth (the magnetic path portions have different circumferential widths) while maintaining symmetry in the critical tip end regions. This allows the structure to have both asymmetric features (for magnetic resistance equalization) and symmetric features (for cogging torque reduction) in different locations.
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 reduces torque ripple when current is applied and cogging torque when no current is applied, specifically minimizing the sixth-order harmonic component of cogging torque.
Implementation Method 1
the magnetic resistance of paths running from a rotor through the different-phase teeth is smaller than that of paths running from the rotor through the same-phase teeth
Implementation Method 2
the amount of current magnetic flux that passes through the different-phase teeth, namely the amount of magnetic flux from permanent magnets of the rotor which passes through the different-phase teeth
Data Source
AI summary
A rotating electrical machine that includes a rotor core having a permanent magnet placed therein; a stator core placed so as to face the rotor core in a radial direction and including a plurality of teeth and a plurality of slots each located between adjacent ones of the teeth; and a plurality of coils placed in the slots of the stator core.