Multi-Stage Rotor Slit Layout for Lower Torque Ripple
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Solution Overview
Problem
Rotating electric machines face challenges in reducing torque ripple while maintaining output torque, as techniques to minimize torque ripple often result in reduced magnet magnetic flux, leading to decreased output torque.
Innovation Solution
A rotating electric machine design featuring a rotor with multiple stages of rotor units, each with arc-like slits and flux barriers, where the arc angle and number of slit rows differ between units, to modulate the magnetic flux and torque ripple, thereby reducing torque ripple without compromising output torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the magnetic center angle of the rotor is allowed to skew by one slot angle of the stator in a rotating direction of the rotor, then the torque ripple is reduced, but the output torque is reduced due to reduced magnetic resistance difference
Solution Approach 1:
The rotor is divided into multiple stages of rotor units stacked in the axial direction, with each stage having different slit configurations (arc angles and number of rows). This segmentation allows each rotor unit to contribute differently to the overall magnetic flux, reducing torque ripple while maintaining output torque through the combined effect of multiple stages with varying characteristics.
Solution Approach 2:
Different rotor units are designed with different local qualities in terms of slit arc angles and number of slit rows. This creates spatial variation in magnetic resistance characteristics along the axial direction, enabling torque ripple reduction in certain regions while preserving output torque through the cumulative magnetic flux from all stages.
2Object-generated harmful factors
If the area of non-magnetic region of the rotor is gradually changed in a laminating direction to moderate the change in magnet magnetic flux interlinked with the stator, then the torque ripple is reduced, but the output torque is reduced due to reduction in magnet magnetic flux
Solution Approach 1:
The rotor is segmented into multiple stages with different slit configurations rather than using a uniform gradual change. Each stage maintains sufficient magnet magnetic flux for output torque while the variation in slit configurations across stages moderates the overall magnetic flux change to reduce torque ripple.
Solution Approach 2:
The rotor employs a composite structure with multiple rotor units having different magnetic characteristics (different arc angles and slit row configurations). This composite approach allows the system to achieve torque ripple reduction through the combined effect of varying magnetic properties while maintaining overall magnetic flux for output torque.
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 design effectively reduces torque ripple and maintains output torque by modulating the magnetic flux and reluctance torque, allowing for improved performance without the drawbacks of previous methods.
Implementation Method 1
each of the plurality of stages of rotor units includes a pair of permanent magnets and a slit arranged in one or more rows in a radial direction of the rotor between the pair of permanent magnets
Implementation Method 2
the slit has an arc-like shape that projects inward in a radial direction of the rotor and extends in a circumferential direction of the rotor
Data Source
AI summary
Provided is a rotating electric machine (100) including a stator (1) and a rotor (2). The rotor (2) includes a plurality of stages of rotor units (201 and 202) stacked in an axial direction. Each of the rotor units (201 and 202) includes a pair of permanent magnets (21) and slits (22a and 22b) arranged in one or more rows. The slits (22a and 22b) has an arc-like shape. Both ends of the arc-like shape are located on an outer periphery side of the rotor (2). When an angle formed between two straight lines that connect positions of both ends of the arc-like shape and a rotation axis center of the rotor (2) is defined as an arc angle, at least one of the arc angle of the slit (22a) and the number of rows of the slits is different between at least two rotor units (201 and 202).