Interior Magnet Motor Rotor Pole Geometry Optimization
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Solution Overview
Problem
Conventional interior magnet motors with hyperbolic rotor shapes face issues of increased cogging torque and harmonic content in induction voltage, leading to vibrations and noise, while attempting to enhance torque output and reduce inductance.
Innovation Solution
A motor design featuring a rotor iron core with laminated high magnetic permeability sheets and strategically placed holes for permanent magnets, where the magnetic pole centerline and boundary line intersect at specific angles, reducing cogging torque and harmonic content by optimizing the magnetic flux interlinking and leakage flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the rotor external shape is formed with a hyperbolic function curve to reduce inductance and increase torque, then the torque output increases and inductance decreases, but the cogging torque increases and harmonic content of induction voltage increases
Solution Approach 1:
The patent changes the geometric parameters of the rotor pole shape by defining specific angle ranges (θ1 between 10-30 degrees, θ2 between 150-170 degrees) for the pole tip configuration. This parameter optimization resolves the contradiction by finding the optimal balance between reducing inductance (for higher torque) and minimizing cogging torque through precise angular control of the pole geometry.
Solution Approach 2:
The patent employs curved surfaces for the rotor pole tips instead of sharp edges or flat surfaces. The rounded pole tip geometry with specifically controlled curvature angles reduces the concentration of magnetic flux at sharp corners, thereby decreasing cogging torque while maintaining the hyperbolic profile for reduced inductance and enhanced torque output.
2Loss of energy
If the rotor external shape is formed with a hyperbolic function curve to reduce inductance, then the inductance decreases and energy is saved, but the harmonic content of induction voltage increases
Solution Approach 1:
The patent optimizes the angular parameters (θ1 and θ2) of the pole tip to achieve the optimal balance between reduced inductance (for energy efficiency) and minimized harmonic content. By controlling these geometric parameters within specific ranges, the design reduces energy losses while suppressing voltage harmonics through smoother magnetic flux distribution.
3Power
If the space between the rotor and stator is reduced to increase torque, then the torque output increases, but the inductance decreases further
Solution Approach 1:
The patent applies different geometric characteristics to different parts of the rotor structure. The pole body maintains a configuration for adequate inductance, while the pole tips are specifically shaped with controlled angles to maximize torque in the reduced air gap. This local differentiation allows the system to achieve high torque with small air gap without excessively compromising inductance.
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 design effectively lowers cogging torque and harmonic content, maintaining output torque while suppressing vibrations and noise, with the magnetic flux interlinking and leakage flux optimized within specific distance and angle ranges.
Implementation Method 1
a rotor having a rotor iron core formed by laminating thin iron-sheets of high magnetic permeability, and held rotatably facing the inner wall of the salient pole iron-core via space. The rotor iron-core has a plurality of holes in which permanent magnets are buried.
Implementation Method 2
a rotor having a rotor iron core formed by laminating thin iron-sheets of high magnetic permeability
Implementation Method 3
formed by laminating thin iron-sheets
Data Source
AI summary
A motor includes a stator formed of a stator iron-core having salient pole iron-cores and windings, and a rotor having a rotor iron-core in which permanent magnets are buried. A magnetic pole centerline connecting a rotary center of the rotor to a magnetic pole center crosses an external shape of the rotor iron-core at end point X, and the magnetic-pole boundary line connecting the rotary center to a magnetic pole boundary point crosses the external shape of the rotor iron-core at end point Z. A straight line angled at a given angle θa from the magnetic pole centerline has end point A. Then a sectional view of the rotor iron-core shows an arc drawn between the end points X and A, and the arc's center is the rotary center. The end points A and Z are connected by one or more than one straight lines in series.