Segmented Permanent Magnet Rotor for Torque Ripple Reduction
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Solution Overview
Problem
In permanent-magnet electrical machines with a radial air gap and a large number of poles, achieving a sinusoidal magnetic flux distribution is challenging, leading to torque vibrations and ripples due to slot harmonics, and the processing and fastening of fragile permanent magnets on curved surfaces are difficult and costly.
Innovation Solution
A new permanent magnet structure with a washer and connecting devices that include straight surfaces for easy fastening and minimal additional material, allowing for sinusoidal flux distribution and reduced manufacturing complexity, while using beveled edges and protective layers to manage torque fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If powerful permanent magnets (such as NdFeB magnets) are used to provide sufficient magnetic field, then the magnetic field strength is improved, but the processing difficulty and cost increase due to their fragility
Solution Approach 1:
The rotor surface is divided into multiple pole regions, and permanent magnets are segmented and fitted into grooves or recesses in the rotor frame. This segmentation allows each magnet to be processed and installed separately, reducing the overall processing difficulty while maintaining strong magnetic fields.
Solution Approach 2:
A rotor frame or magnet holder is introduced as an intermediary structure between the permanent magnets and the rotor surface. This frame provides mechanical support and protection for the fragile magnets, making them easier to handle and install while maintaining their magnetic field strength.
2Reliability
If permanent magnets are fastened on the rotor's curved surface using processing methods (straightening rotor surface or concave magnet surface), then the fastening reliability is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
Instead of processing the curved rotor surface to be straight or processing the magnet surface to be concave, the invention inverts the approach by providing a pre-formed rotor frame with grooves or recesses that naturally accommodate the magnets. This reduces processing complexity while maintaining fastening reliability.
Solution Approach 2:
The invention changes the geometric parameters of the rotor frame by introducing grooves, recesses, or slots with specific dimensions that match the permanent magnets. This parameter change allows simple fastening methods (such as adhesive bonding or mechanical retention) to achieve reliable fastening without complex processing.
3Reliability
If fastening means are used to secure permanent magnets between the poles, then the fastening reliability is improved, but the space available for permanent magnets in the circumferential direction is reduced
Solution Approach 1:
The fastening function is merged with the rotor frame structure itself. The rotor frame includes integrated grooves, recesses, or slots that both support the magnets and provide fastening functionality, eliminating the need for separate fastening means and preserving magnet volume.
Solution Approach 2:
The rotor frame is designed with multi-functionality: it provides magnetic circuit support, structural support, and fastening functionality all in one component. This universal design eliminates the need for additional fastening elements that would reduce the available space for permanent magnets.
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 solution effectively minimizes cogging torque and torque ripple within specified limits during idling and load conditions, ensuring efficient operation and cost-effective manufacturing by maintaining even magnetic flux density and reducing processing complexity.
Implementation Method 1
The permanent magnets are used for establishing a magnetic field, and the magnetic flux of the field goes over the air gap to the stator
Implementation Method 2
inside the rotor's magnetically conductive frame
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The object of the invention is an electric machine with a permanent magnet rotor where the permanent magnets have been fitted on the outer surface of a cylindrical rotor, and a permanent magnet. The permanent magnets forming the electric machine's rotor pole have been shaped so that the electric machine's air gap is essentially constant in the middle of the pole, and the air gap increases in an essentially straightforward manner when moving towards the edge of the pole. The permanent magnet is of an even thickness in the middle, and becomes thinner towards the edges. The object of the invention also is a permanent magnet and a method for decreasing the torque ripple and cogging torque of an electric machine.