Segmented Rotor Magnet Structure for Air-Gap Harmonic Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

New energy vehicle motors face challenges in reducing harmonic components of the rotor air gap magnetic field, leading to eddy current losses in permanent magnets and alternating current losses in windings during high-speed operations, which affects torque and power density.

Innovation Solution

The method involves dividing an ideal sinusoidal air gap magnetic field wave into segments, aligning the tooth portions of the rotor's magnet components with these segments to form air gap magnetic field harmonics closer to the ideal sinusoidal wave, using analog pulse width modulation to reduce harmonic components, AC losses, and eddy current losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If full pitch winding is adopted for high-speed operation, then the motor can operate at high speed, but significant alternating current loss is generated due to air gap magnetic field harmonics

Engineering Contradiction:

Improvemotor speedVSAvoidalternating current loss

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The rotor magnet component is divided into multiple segments along the circumferential direction, with each segment having a specific width. By segmenting the magnet and arranging them with different widths, the patent creates a non-uniform magnetic field distribution that reduces harmonic components in the air gap magnetic field, thereby reducing alternating current losses while maintaining high-speed operation capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different segments of the rotor magnet have different local properties, specifically different widths. The first segment has a different width than the second segment, creating localized variations in magnetic field strength and distribution. This local quality variation helps eliminate harmonic components and reduces energy losses during high-speed operation

Inventive Principle:

Principle #3Local quality

2Device complexity

If conventional rotor structure is used, then the motor structure is simple, but eddy current losses occur in permanent magnets due to harmonic components in air gap magnetic field

Engineering Contradiction:

Improverotor structure complexityVSAvoideddy current loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The rotor magnet is segmented into multiple sections with different widths arranged circumferentially. This segmentation creates a specific magnetic field distribution pattern that reduces harmonic components, thereby reducing eddy current losses in the permanent magnets while maintaining a relatively simple overall rotor structure that can be manufactured using conventional processes

Inventive Principle:

Principle #1Segmentation

3Force

If the tooth portion area is increased to strengthen magnetic field, then magnetic field strength is improved, but harmonic components of air gap magnetic field increase

Engineering Contradiction:

Improvemagnetic field strengthVSAvoidharmonic components

Core Design Contradiction:

ForceVSObject-generated harmful factors

Solution Approach 1:

Instead of uniformly increasing the tooth portion area, the patent applies local quality variation by setting different widths for different segments of the rotor magnet. The first segment has a different width than the second segment, creating localized magnetic field enhancements that maintain overall magnetic field strength while reducing harmonic components through the non-uniform distribution pattern

Inventive Principle:

Principle #3Local quality

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 effectively reduces harmonic components of the air gap magnetic field, minimizing AC losses, eddy current losses, and motor vibrations, thereby enhancing the motor's performance and applicability at high speeds.

Implementation Method 1

air gap magnetic field harmonics close to the ideal sinusoidal air gap magnetic field wave are formed

Methodology Applied

Scientific EffectMagnetic field harmonics: Magnetic Field

Implementation Method 2

eddy current losses of magnets during the high-speed operation of the motor

Methodology Applied

Scientific EffectEddy current losses: Eddy Currents

Data Source

PatentUS20250015643A1Rotor structure and forming method therefor, and electric motor structure

Publication Date: 2025.01.09 ZHEJIANG FOUNDER MOTOR

AI summary

The present disclosure provides a method for forming a rotor structure, including: providing a plurality of magnet units, wherein each of the plurality of magnet units comprises a magnet component having a plurality of tooth portions; and dividing an ideal sinusoidal air-gap magnetic field wave into N segments, wherein when the center line of a tooth portion of the plurality of tooth portions is in a corresponding segment of the ideal sinusoidal air-gap magnetic field wave, the area of the tooth portion is equal to the area of the corresponding segment of the ideal sinusoidal air gap magnetic field wave. The present disclosure further provides a rotor structure formed by the method according to the present disclosure, and a motor structure including the rotor structure.