IPM Rotor Magnet Orientation for Demagnetization Resistance
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Solution Overview
Problem
Interior permanent magnet (IPM) rotors in rotary electric machines face demagnetization issues due to high excitation currents, leading to irreversible demagnetization of permanent magnets, especially when field-weakening control is employed, which increases the risk of demagnetization and requires costly materials or increased magnet thickness to mitigate.
Innovation Solution
The design incorporates a configuration where auxiliary magnets with specific magnetic orientations are placed at the q-axis and d-axis ends of main magnets, intersecting with the main magnets' orientations to enhance demagnetization resistance, using a combination of main and auxiliary magnets with different coercive forces to optimize magnetic flux and reduce demagnetization risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If field-weakening control is employed to increase rotational speed, then rotational speed is improved, but demagnetization risk of permanent magnets increases
Solution Approach 1:
The patent applies local quality by providing different magnetic orientations at different locations within the same magnet. The q-axis side end has magnetic orientations closer to the q-axis direction, while the d-axis side end has magnetic orientations closer to the d-axis direction. This local differentiation strengthens the magnetic flux at the vulnerable q-axis side end without compromising the overall magnet performance, thereby improving demagnetization resistance specifically where needed while maintaining high rotational speed capability.
Solution Approach 2:
The patent introduces a new dimension of magnetic orientation control by varying the magnetic orientation angles within the magnet volume. Instead of uniform orientation, the magnetic orientations are distributed across different angles, with the q-axis side end having orientations closer to the q-axis and the d-axis side end having orientations closer to the d-axis. This dimensional approach to magnetic orientation provides enhanced demagnetization resistance while maintaining speed performance.
2Reliability
If magnet thickness is increased to improve demagnetization resistance, then demagnetization resistance is improved, but device complexity and material costs increase
Solution Approach 1:
Rather than uniformly increasing magnet thickness throughout, the patent applies local quality by concentrating enhanced magnetic flux strength specifically at the q-axis side end where demagnetization risk is highest. This is achieved through localized magnetic orientation control, where the q-axis side end has magnetic orientations closer to the q-axis direction. This approach improves demagnetization resistance at the vulnerable location without requiring increased overall magnet thickness, thereby avoiding additional material costs and structural complexity.
3Reliability
If expensive heavy rare earth elements are used to improve demagnetization resistance, then demagnetization resistance is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies parameter changes by modifying the magnetic orientation parameters within the existing magnet material. Instead of changing the material composition to expensive heavy rare earth elements, the invention changes the magnetic orientation angles and distributions. The q-axis side end has magnetic orientations closer to the q-axis direction, and the d-axis side end has magnetic orientations closer to the d-axis direction. This parameter-based solution achieves improved demagnetization resistance while maintaining cost-effective material selection.
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 configuration effectively reduces demagnetization of main magnets by strengthening magnetic flux at vulnerable ends, improving demagnetization resistance without increasing material costs or complexity, allowing for more efficient operation under high demagnetization fields.
Implementation Method 1
Each of the magnets includes a first magnet member configured to generate magnet flux in accordance with a corresponding one of the polarities. The first magnet member has first magnetic orientations defined therein. Each of the magnets includes a second magnet member provided at a q-axis side end of the corresponding magnet located closer to a pole boundary. The second magnet member has second magnetic orientations defined therein, and the second magnetic orientations intersect with the first magnetic orientations.
Data Source
AI summary
A rotor of a rotary electric machine includes magnets arranged to face a winding. The magnets are movable relative to the winding upon the winding being energized. The magnets are arranged in a relative movement direction while magnetic polarities based on the magnets are alternately changed. Each magnet includes a first magnet member configured to generate magnet flux in accordance with a corresponding one of the polarities. The first magnet member has first magnetic orientations defined therein. Each magnet includes a second magnet member provided at a q-axis side end of the corresponding magnet located closer to a pole boundary. The second magnet member has second magnetic orientations defined therein. The second magnetic orientations intersect with the first magnetic orientations.