IPM Rotor Voids Reduce Torque Ripple
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Solution Overview
Problem
Interior permanent magnet electric machines experience cogging torque, leading to torque ripple and speed ripple due to the interaction of rotor and stator magnetic poles, which limits their performance.
Innovation Solution
The electric machine features a rotor core with magnetically permeable material, including discrete axially extending magnet slots and voids positioned between the magnet slots, which are designed to reduce torque ripple by optimizing the placement and size of permanent magnets and voids, enhancing the rotor's magnetic field distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional rotor configuration with continuous magnet slots is used, then manufacturing is simpler, but torque ripple increases due to cogging torque
Solution Approach 1:
The rotor core is segmented into multiple magnetic poles with discrete magnet slots, and voids are introduced to further segment the magnetic structure. This segmentation disrupts the continuous magnetic path that causes cogging torque, thereby reducing torque ripple while maintaining manufacturability through standardized slot and void patterns.
Solution Approach 2:
Voids are strategically positioned at specific locations within the rotor core, particularly in the bridge regions between adjacent magnetic poles. This local modification creates non-uniform magnetic permeability distribution that specifically targets the reduction of cogging torque without compromising the overall structural integrity or manufacturing process.
2Object-generated harmful factors
If voids are added to reduce torque ripple, then torque ripple decreases, but rotor structural complexity increases
Solution Approach 1:
The rotor structure is divided into repeating modular units, each containing magnet slots and voids in standardized positions. This modular segmentation allows the complex voided structure to be manufactured using repetitive processes, reducing the practical complexity despite the increased geometric complexity.
Solution Approach 2:
The voids are positioned asymmetrically within the rotor core structure, specifically in the bridge regions between poles, to create an optimized magnetic flux distribution. This asymmetric placement targets the specific locations where cogging torque is generated, achieving torque ripple reduction with minimal additional structural complexity.
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 configuration significantly reduces torque ripple across various load conditions, improving the overall performance and efficiency of the electric machine by maintaining mechanical strength and structural integrity while enhancing magnetic field distribution.
Implementation Method 1
permanent magnets mounted therein to provide the rotor field
Implementation Method 2
interaction of rotor and stator magnetic poles
Implementation Method 3
rotor core formed out of magnetically permeable material
Data Source
AI summary
An electric machine having a rotor with a rotor core formed out of magnetically permeable material and defines a plurality of poles. Each pole includes a plurality of discrete axially extending magnet slots with at least one permanent magnet in each magnet slot. Each pole has a radial centerline and includes a plurality of voids defined by the rotor core. For each pole the magnet slots include at least one central magnet slot and two outer magnet slots, the outer magnet slot are positioned on opposite circumferential sides of the radial centerline of the pole and are at least partially positioned radially outwardly of a radially outermost edge of the at least one central magnet slot. Each of the plurality of voids is spaced from each of the magnet slots and positioned circumferentially between the outer magnet slots and radially outwardly of the at least one central magnet slot.