Squirrel-Cage Rotor End Ring Stress Relief
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Solution Overview
Problem
In squirrel-cage rotors, high-speed rotation leads to excessive stress concentration on the end ring due to centrifugal force, causing potential damage when the conductor bar's shape is similar to the end ring's fitting portion with a small circular arc radius, resulting in stress concentration issues.
Innovation Solution
A squirrel-cage rotor design with a circular arc gap on the rotor central axis side of the fitting portion, where the gap's radius is larger than the conductor bar's circular arc radius, and a tapering cross-sectional shape of the conductor bar, reducing stress concentration by distributing the force more evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the conductor bar shape is similar to the end ring fitting portion with a small circular arc radius, then the conductor bar fits well in the slot, but excessive stress is concentrated on the end ring during high-speed rotation
Solution Approach 1:
The invention applies different geometric characteristics to different parts of the conductor bar. The outer circumferential side maintains a shape matching the slot for secure fitting, while the rotor central axis side uses a circular arc shape with larger radius that matches the gap in the end ring fitting portion. This local differentiation allows the conductor bar to fit precisely in the slot while avoiding stress concentration at the critical fitting portion interface.
2Stability of the object's composition
If the width of teeth is kept constant, then the magnetic force lines passage is uniform, but the slot width decreases toward the central axis causing stress concentration
Solution Approach 1:
The conductor bar is designed with varying cross-sectional characteristics along its length. The portion corresponding to the tooth region maintains dimensions for proper magnetic circuit integration, while the portion at the rotor central axis side adopts a circular arc shape with larger radius to match the increased gap width, thereby distributing stress evenly without compromising magnetic circuit uniformity.
3Power
If the rotor rotates at high speed, then the power output increases, but large centrifugal force damages the end ring
Solution Approach 1:
The end ring fitting portion is designed with a gap and a circular arc shape with larger radius before the rotor undergoes high-speed rotation. This pre-designed geometric feature acts as a stress-relief mechanism that prevents stress concentration from developing during high-speed operation, thereby cushioning against centrifugal force damage before it occurs.
Solution Approach 2:
The invention changes the geometric parameters of the conductor bar and end ring fitting portion. The circular arc radius of the conductor bar at the rotor central axis side is made larger than the gap radius in the end ring fitting portion. This parameter modification reduces stress concentration and prevents end ring damage during high-speed rotation while maintaining power output capability.
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 stress concentration on the end ring, preventing damage and ensuring the rotor's integrity during high-speed operation.
Implementation Method 1
When the rotor is rotated at high speed, large rotation centrifugal force is applied to the end ring, and excessive stress is concentrated on the end on the rotor central axis side in the fitting portion of the end ring
Data Source
AI summary
A squirrel-cage rotor includes a rotor core having in its circumferential direction a plurality of slots extending in an axial direction, a plurality of conductor bars stored in each slot of the rotor core and whose ends are projected from an axial direction end surface of the rotor core, and a pair of end rings arranged at the ends of the rotor core and each having a plurality of fitting portions into which the both ends of the conductor bars projecting from the axial direction end surface of the rotor core are fitted. In the conductor bar, among the cross-sectional shape in a plane perpendicular to the axial direction, the shape on the rotor central axis side is a circular arc shape. In the plane perpendicular to the axial direction, a gap is provided on the rotor central axis side of the fitting portion fitted with the conductor bar.