PMSM Rotor Surface Grooves for Torque Ripple Reduction
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Solution Overview
Problem
Permanent magnet synchronous motors face challenges with cogging torque and torque ripple, particularly in low torque areas, due to nonlinear magnetic circuits and rich back EMF harmonic content, leading to increased noise, vibration, and harshness, and existing solutions like skewed stator or rotor slotting increase costs and complexity without substantial reductions in these issues.
Innovation Solution
A permanent magnet synchronous motor design featuring a rotor with q-axis and d-axis surface grooves on the iron core, reducing cogging torque and torque ripple by minimizing air gap flux density distortion, with a simple structure and low manufacturing costs, utilizing 24 stator teeth and 8 pole magnet plates, and optimizing groove dimensions and shapes to enhance sinusoidal flux density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If rotor step skewing or rotator skewed slot is employed to reduce cogging torque and torque ripple, then back EMF harmonic content and cogging torque are reduced, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The rotor is divided into multiple laminations stacked together, with each lamination having a specific skew angle. This segmentation allows the complex skewing effect to be achieved through simple stacking of standard components, reducing manufacturing complexity while maintaining the torque ripple reduction benefit
Solution Approach 2:
The invention changes the skew angle parameter of rotor laminations to optimize the cancellation of cogging torque and back EMF harmonics. By adjusting this single parameter, the motor achieves reduced torque ripple without requiring complex structural modifications
2Object-generated harmful factors
If rotor step skewing is employed to reduce cogging torque, then harmonic content is reduced, but peak torque and peak power decrease by 10%
Solution Approach 1:
Instead of applying full skewing to all rotor laminations, the invention uses partial skewing where only certain laminations have skew angles while others remain uns skewed. This partial application maintains peak torque capability while still achieving sufficient harmonic cancellation for torque ripple reduction
3Object-generated harmful factors
If rotator skewed slot or rotor step skewing is employed to reduce torque ripple, then cogging torque is reduced, but bearing reliability decreases due to cyclic axial force
Solution Approach 1:
The invention introduces asymmetric groove structures on the rotor surface that create a counterbalancing magnetic force distribution. This asymmetric design compensates for the cyclic axial forces generated by skewing, thereby protecting bearing reliability while maintaining torque ripple reduction
4Power
If magnet consumption is increased by 10% to compensate for capacity loss from rotor step skewing, then original motor capacity is restored, but manufacturing cost increases significantly
Solution Approach 1:
The invention optimizes the skew angle parameters to achieve the best balance between maintaining motor capacity and reducing torque ripple. By carefully selecting specific skew angle values, the design minimizes capacity loss, thereby reducing the need for additional magnet material and controlling manufacturing costs
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 significantly reduces cogging torque and torque ripple, especially in low torque areas, while maintaining a simple and cost-effective manufacturing process, improving the motor's performance and reducing noise and vibration.
Implementation Method 1
reducing cogging torque and torque ripple by minimizing air gap flux density distortion, with a simple structure and low manufacturing costs, utilizing 24 stator teeth and 8 pole magnet plates, and optimizing groove dimensions and shapes to enhance sinusoidal flux density
Data Source
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AI summary
The present invention discloses a permanent magnet synchronous motor, a rotor thereof comprising an iron core in cylindrical form, with p S pole magnet plates and p N pole magnet plates arranged inside of the iron core around an axis thereof, wherein p is a positive integer, and the p S pole magnet plates and the p N pole magnet plates are alternatively aligned; on a surface of a rotor iron core of each magnet steel plate are arranged two d axial surface grooves; the two d axial surface grooves corresponding to each magnet steel plate are situated on two sides of a center line of the magnet steel plate; an inter-axial distance of the two d axial surface grooves of each magnet steel plates is approximately equal to a tooth tip span of a rotor tooth of the permanent magnet synchronous motor. The present invention also discloses a rotor of a permanent magnet synchronous motor. The permanent magnet synchronous motor and the rotor of the present invention reduces torque ripple in the torque area, has a simple structure and low cost, and is easy to manufacture.