Permanent Magnet Motor Torque Ripple Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing permanent magnet motors face challenges in reducing torque ripple, particularly with concentrated winding configurations, where stator slot skewing and rotor step skewing are limited, and stator teeth notching and arc modification on the rotor surface only partially address the issue, especially concerning the sixth-harmonic ripple.
Innovation Solution
A permanent magnet motor design featuring a stator assembly with a yoke portion, tooth portions, and winding slots, and a rotor assembly with surface-mounted permanent magnets and a rotor sheath divided into segments with varying magnetic conductivity, along with grooves on the tooth portions and a fractional-slot winding configuration, to minimize torque ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If stator slot skewing or rotor step skewing is applied, then torque ripple is reduced, but the number of slots must be relatively few which limits the design flexibility and fundamental wave torque
Solution Approach 1:
The rotor sheath is divided into multiple segments along the axial direction, with each segment having different magnetic conductivity properties. This segmentation allows independent optimization of magnetic field distribution in different axial regions, reducing torque ripple while maintaining design flexibility for concentrated winding configurations with any number of slots.
Solution Approach 2:
Different segments of the rotor sheath are assigned different magnetic conductivity characteristics to create localized magnetic field modifications. This local quality differentiation enables targeted reduction of specific harmonic components of torque ripple without affecting the overall fundamental wave torque, resolving the contradiction between ripple reduction and design flexibility.
2Object-generated harmful factors
If rotor sheath made of magnetic material is used, then magnetic field distribution is skewed which reduces torque ripple, but magnetic conductivity varies along axial direction requiring segmented structure
Solution Approach 1:
The rotor sheath is divided into multiple axially-oriented segments with different magnetic conductivity properties. This segmentation transforms the complex continuous variation requirement into discrete, manufacturable sections that can be independently produced and assembled, reducing manufacturing complexity while achieving the desired magnetic field skewing effect for torque ripple reduction.
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 design effectively reduces torque ripple by creating a skewed magnetic field distribution and back reaction, decreases sixth-harmonic torque, and maintains high fundamental wave torque, while also enhancing flux density and motor output.
Implementation Method 1
The magnetic conductivity of a first segment of the rotor sheath is different from a magnetic conductivity of a second segment of the rotor sheath
Implementation Method 2
The permanent magnets are disposed at intervals on a surface of the rotor core and magnetic poles of two facing sides of adjacent permanent magnets are the same
Data Source
AI summary
A permanent magnet motor, including: a stator assembly and a rotor assembly. The stator assembly includes: a stator core and a coil winding. The stator core includes: a yoke portion, a plurality of tooth portions, and a plurality of winding slots. The rotor assembly includes: a rotor core, a plurality of permanent magnets, and a rotor sheath. The tooth portions are extended out of the yoke portion. Each winding slot is formed between adjacent tooth portions. The permanent magnets are disposed at intervals on a surface of the rotor core and magnetic poles of two facing sides of adjacent permanent magnets are the same. The rotor sheath is disposed outside the rotor assembly and is divided into at least two segments axially. A magnetic conductivity of a first segment of the rotor sheath is different from a magnetic conductivity of a second segment of the rotor sheath.