Complementary Permanent Magnet Structure for Rotating Electric Machine Cogging Torque Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rotating electric machines experience undesired output torque ripple and vibration due to cogging torque, which is challenging to minimize without reducing the effective output magnetic torque or increasing manufacturing costs and time.
Innovation Solution
A complementary permanent magnet structure with a cylinder-shaped magnetic pole core and ring-shaped armature core, where the number of slots to magnetic poles is 3/2, and two complementary cogging torques with 180 degrees of electrical angle difference are generated by adjusting the shapes and sizes of first and second permanent magnet units to counterbalance the cogging torques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If skew tooth slot or skew magnetic pole is used to reduce the rate of change of equivalent magnetic reluctance, then cogging torque is reduced, but manufacturing cost and time increase
Solution Approach 1:
The magnetic pole core is segmented into multiple magnetic pole cores, and the armature core is segmented into multiple armature cores. This segmentation allows the cogging torque to be distributed and reduced without requiring complex skewing operations, thereby maintaining ease of manufacture while achieving cogging torque reduction
Solution Approach 2:
Instead of skewing the tooth slot or magnetic pole to reduce cogging torque (conventional approach), this invention inverts the approach by using multiple magnetic pole cores and armature cores with specific slot-to-pole ratios. This alternative method achieves the same goal of reducing cogging torque without the manufacturing complexity of skewing operations
2Object-affected harmful factors
If specific ratio of slots to magnetic poles is used to reduce cogging torque, then cogging torque is minimized, but radial forces occur causing vibration and noise
Solution Approach 1:
Multiple magnetic pole cores and multiple armature cores are merged into a single integrated structure. This merging allows the cogging torque from different core combinations to counterbalance each other, reducing overall cogging torque while distributing radial forces to minimize vibration and noise
Solution Approach 2:
The invention uses counterbalancing principles by configuring multiple magnetic pole cores and armature cores such that their respective cogging torques act in opposite directions. This counterweight effect cancels out the harmful radial forces and reduces vibration and noise while maintaining the benefits of reduced cogging torque
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 the peak cogging torque by 70-80% without additional manufacturing costs or time, achieving minimized cogging torque in rotating electric machines.
Implementation Method 1
A magnetic reluctance torque, also referred to as stop torque, is caused due to the rate of change of the magnetic reluctance in response to the rotating angle and is proportional to the square of the equivalent magnetic flux in the air gap. The torque generated by the constant magnetic field from the permanent magnet in order to match the minimum equivalent magnetic reluctance in the magnetic flux path of the core is referred to as a cogging torque.
Implementation Method 2
When a permanent magnet is used as a constant magnetic source rotating without a load, the characteristics in the magnetic flux path of the rotating electric machine are controlled by the constant magnetic field.
Data Source
AI summary
A complementary permanent magnet structure capable of minimizing the cogging torque for a rotating electric machine, the complementary permanent magnet structure comprising: a magnetic pole core being cylinder shaped with even numbered arc-shaped magnetic sets positioned with equal distances on the circumference thereof, each magnetic set being composed of a first permanent magnet unit and a second permanent magnet unit; and an armature core being ring shaped with a plurality of slots; wherein the ratio of the number of the slots to the number of magnetic poles of the magnetic pole core is 3/2; wherein the first permanent magnet unit and the second permanent magnet unit are positioned correspondingly to generate two complementary cogging torques with 180 degrees of electrical angle difference.