IPM Motor Permanent Magnet Thickness Profile for Demagnetization Resistance
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Solution Overview
Problem
IPM synchronous motors face demagnetization issues due to reverse magnetic fields, leading to potential demagnetization of permanent magnets, which can result in reduced performance, reliability, and increased costs, especially when high demagnetization resistance is required.
Innovation Solution
The motor design incorporates outermost peripheral and inner permanent magnets with specific thickness profiles, where central portions of inner magnets are thinner and end portions are thicker than the outermost peripheral magnet, optimizing d-axis magnetic flux and demagnetization resistance without increasing the magnet amount significantly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of permanent magnet is increased to design a motor having high torque and high demagnetization resistance, then torque and demagnetization resistance are improved, but cost and volume and mass of product increase
Solution Approach 1:
The patent applies local quality by creating non-uniform thickness distribution in permanent magnets. The outermost peripheral permanent magnet has uniform thickness, while inner permanent magnets have thinner central portions and thicker end portions. This local variation optimizes the balance between torque generation (requiring sufficient magnet volume) and demagnetization resistance (requiring adequate magnetic flux paths), thereby improving reliability without proportionally increasing overall magnet amount.
Solution Approach 2:
The patent transitions from considering only the radial thickness of permanent magnets to incorporating the dimensional distribution pattern across different radial positions. By varying thickness in the radial direction differently for inner versus outer magnets, and by creating thickness variations through the arc angle, the design optimizes performance in multiple dimensional aspects simultaneously, achieving better torque and demagnetization resistance without linear scaling of material quantity.
2Reliability
If a demagnetizing factor is taken into account in design by taking a margin, then demagnetization resistance is improved, but cost increases due to larger margin requirement
Solution Approach 1:
The patent changes the geometric parameters of permanent magnets specifically - varying the thickness distribution pattern between outermost and inner magnets. This parameter optimization inherently improves demagnetization resistance by creating more favorable magnetic flux paths, thereby reducing the need for excessive design margins and associated cost increases.
3Power
If the arc angle of permanent magnet is increased to increase magnet torque, then magnet torque is improved, but the distance between end portions of permanent magnets decreases causing demagnetization
Solution Approach 1:
The patent applies local quality by differentiating the thickness characteristics between outermost peripheral permanent magnets and inner permanent magnets. The inner magnets have thinner central portions which increase the magnetic flux path distance, thereby improving demagnetization resistance even when arc angles are optimized for high torque. This localized differentiation allows torque optimization without compromising reliability.
Solution Approach 2:
The patent segments the permanent magnet structure into distinct radial zones with different thickness characteristics. By dividing the magnet arrangement into outermost peripheral magnets and inner magnets with different geometric properties, the design can optimize torque generation in the inner region while maintaining demagnetization resistance through the structural segmentation.
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 enhances torque and demagnetization resistance while maintaining a compact motor design at a lower cost, by increasing d-axis magnetic flux and magnet torque without saturating the magnetic flux, thus preventing demagnetization.
Implementation Method 1
The magnet torque is torque which is generated by attraction and repulsion between a permanent magnet and a rotating magnetic field, and is generated by a permanent magnet embedded in a motor.
Implementation Method 2
The reluctance torque is torque which is generated by saliency in which magnetoresistance changes depending on the position of a rotor. The flow of a magnetic flux in a d-axis direction passes through a permanent magnet having small magnetic permeability, and therefore, electromagnetic resistance becomes greater, and thus the d-axis inductance Ld becomes greater.
Data Source
AI summary
A motor includes a stator that generates a rotating magnetic field; a rotor supported rotatably by a shaft within the stator; an outermost peripheral permanent magnet that is a permanent magnet embedded inside the rotor in an arced shape forming a convexity at the inner surface of the rotor; and an inner permanent magnet that is a permanent magnet embedded at the inside of the rotor in parallel to the outermost peripheral permanent magnet. The arc angle of the permanent magnets is greater than 90°, the thickness at the center of both inner permanent magnets is thinner than the thickness at the center of the outermost peripheral permanent magnet, and the thickness at the ends of both inner permanent magnets is thicker than the thickness at the ends of the outermost peripheral permanent magnet.