Permanent-Magnet Segment Demagnetization for Low-Cogging Electric Machines
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Solution Overview
Problem
Existing electric machines with permanent-magnet and electromagnet arrangements suffer from torque ripple and cogging due to magnetic interactions, which negatively affect rotation speed control and mechanical robustness, as existing design measures to reduce these issues weaken the magnet segments.
Innovation Solution
The solution involves creating demagnetized regions within the permanent-magnetic material instead of removing or recessing it, maintaining mechanical robustness while reducing torque ripple and cogging by altering the magnetic field profile, and using a magnetic return path element for field line guidance and structural support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If detached pole portions are created by flattening end sections of magnet segments, then torque ripple and cogging are reduced, but mechanical robustness of magnet segments is weakened
Solution Approach 1:
The patent applies parameter changes by modifying the magnetic properties of the permanent-magnetic material through controlled demagnetization in specific regions, rather than changing the physical geometry of the magnet segments. This allows creating demagnetized regions that reduce torque ripple while preserving the complete mechanical structure of the magnet segments, thus maintaining their mechanical robustness.
Solution Approach 2:
The patent replaces the mechanical approach (removing or flattening material to create detached pole portions) with a magnetic field approach (creating demagnetized regions through controlled demagnetization). This substitution allows achieving the same magnetic field profile effects without compromising the mechanical integrity of the magnet segments.
2Object-generated harmful factors
If additional recesses are created in magnet segments between end sections, then torque ripple and cogging are further reduced, but the structure of permanent-magnetic material is weakened causing magnet segments to break
Solution Approach 1:
The patent changes the magnetic parameter (magnetization state) rather than the physical structure. By creating demagnetized regions through controlled demagnetization processes, the patent achieves reduced cogging without removing any material, thus preserving the complete structural integrity and reliability of the magnet segments.
Solution Approach 2:
The patent substitutes the mechanical modification approach (creating physical recesses) with a magnetic field modification approach (creating demagnetized regions). This allows achieving the desired magnetic field profile for reduced cogging while maintaining the full mechanical strength and reliability of the magnet segment structure.
3Object-generated harmful factors
If magnet segments are designed with complex shapes to reduce torque ripple, then magnetic field profile is optimized, but manufacturing complexity and technical implementability increase
Solution Approach 1:
The patent simplifies manufacturing by changing the magnetic parameter (magnetization state) of existing magnet segments rather than requiring complex geometric shaping. The demagnetized regions are created through controlled demagnetization processes, which are simpler to implement than precision mechanical machining of complex magnet segment shapes.
Solution Approach 2:
The patent replaces complex mechanical manufacturing operations (precision machining of detached pole portions and recesses) with a magnetic field-based process (controlled demagnetization). This substitution significantly improves ease of manufacture and technical implementability while achieving the same magnetic field optimization for reduced torque ripple.
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 allows for a more robust permanent-magnet arrangement with a reduced torque ripple and cogging, enabling efficient rotation speed control without compromising the mechanical integrity of the magnet segments, and simplifies production by allowing for various magnetic field configurations.
Implementation Method 1
The magnet segments have a permanent magnetization in a first magnet segment volume
Implementation Method 2
At least one magnet segment has a demagnetized region in a second magnet segment volume
Implementation Method 3
The electromagnet arrangement has a first number of field coils which are each wound around a pole core
Data Source
AI summary
The invention relates to an electric machine comprising a permanent magnet arrangement and an electromagnetic arrangement. The electromagnetic arrangement comprises a first number of excitation coils, each excitation coils being wound around a pole core. The permanent magnet arrangement comprises a second number of magnet segments formed of a permanently magnetic material. An air gap is arranged between the electromagnet arrangement and the permanent magnet arrangement. The magnet segments have a permanent magnetisation in a first magnet segment volume. At least one magnet segment comprises a demagnetised region in a second magnet segment volume.