Split Rotor Motor Torque Ripple Cancellation
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Solution Overview
Problem
Conventional brushless motors with split rotors face challenges in achieving suitable magnetic characteristics due to complex magnetic flux flow and torque ripples, primarily because of the special shape of permanent magnets on the inner rotor.
Innovation Solution
The design incorporates a rotor with two rotating bodies, each having a cylindrical shape with outer side surfaces curved in a circular arc, where the curvature radii of the first and second outer side surfaces differ, allowing for simplified magnetic flux flow and opposing torque ripple phases to cancel each other out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If permanent magnets on the inner rotor are given a special shape to suppress cogging torque, then cogging torque is reduced, but the flow of magnetic flux becomes complicated and suitable magnetic characteristics cannot be obtained
Solution Approach 1:
The rotor is divided into two separate rotating bodies (first and second rotating bodies), each with its own set of permanent magnets. This segmentation allows independent optimization of each rotating body's magnet shape and configuration, enabling cogging torque suppression while maintaining simple magnet shapes for good magnetic characteristics.
Solution Approach 2:
The first and second rotating bodies are positioned asymmetrically in the circumferential direction, with their magnetic poles shifted relative to each other. This asymmetric arrangement allows the torque ripples generated by each rotating body to have opposite phases, causing them to cancel each other out and reduce overall torque ripples while maintaining simple magnet geometries.
2Object-affected harmful factors
If the rotor is divided into two parts with shifted permanent magnets to suppress cogging torque, then cogging torque is reduced, but torque ripples are generated due to complex magnetic flux flow
Solution Approach 1:
The first and second rotating bodies are positioned asymmetrically in the circumferential direction, creating opposite phase torque ripples that cancel each other. The asymmetric positioning ensures that when one rotating body generates positive torque ripple, the other generates negative torque ripple of equal magnitude, achieving ripple cancellation.
Solution Approach 2:
The second rotating body acts as a counterweight to the first rotating body in terms of magnetic torque generation. By positioning the magnetic poles of the second rotating body at a specific offset from the first, the torque ripples generated by each body are equal in magnitude but opposite in phase, causing them to neutralize each other's harmful effects.
3Reliability
If permanent magnets are arranged with complex shapes to achieve suitable magnetic characteristics, then magnetic characteristics are improved, but device complexity increases
Solution Approach 1:
By dividing the rotor into two separate rotating bodies, each with simple rectangular or block-shaped permanent magnets, the patent achieves suitable magnetic characteristics without complex magnet geometries. The segmentation allows the simple shapes to be optimally positioned to generate the desired magnetic field distribution and torque characteristics.
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 torque ripples and cogging torque, enhancing motor stability and magnetic characteristics by aligning the phases of torque ripples generated in each rotating body.
Implementation Method 1
a stator core having a cylindrical shape with the central axis as a center and a plurality of coils arranged in the circumferential direction; a plurality of first magnets arranged in the circumferential direction on a first rotor core; a plurality of second magnets arranged in the circumferential direction on a second rotor core
Implementation Method 2
An outer side surface of the first rotating body includes a plurality of first outer side surfaces curved in a circular arc shape in a plan view and arranged in the circumferential direction. The first outer side surface is an outer side surface of the first magnet or an outer side surface of the first rotor core. An outer side surface of the second rotating body includes a plurality of second outer side surfaces curved in a circular arc shape in a plan view and arranged in the circumferential direction. The second outer side surface is an outer side surface of the second magnet or an outer side surface of the second rotor core, and a curvature radius of the first outer side surface is different from a curvature radius of the second outer side surface.
Data Source
AI summary
A rotor includes a first rotating body and a second rotating body. The first rotating body includes a first rotor core and first magnets arranged in a circumferential direction. An outer side surface of the first rotating body includes first outer side surfaces curved in a circular arc shape and arranged in the circumferential direction. The first outer side surface is an outer side surface of the first magnet or an outer side surface of the first rotor core. The second rotating body is positioned on a side lower than the first rotating body in an axial direction and includes a second rotor core and second magnets arranged in the circumferential direction. An outer side surface of the second rotating body includes second outer side surfaces curved in a circular arc shape and arranged in the circumferential direction.