Rotor Core Crack Removal via Through-Hole Segmentation
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Solution Overview
Problem
Conventional methods for removing cracks in electromechanical rotors are cumbersome and ineffective in preventing crack growth, as they require machining of narrow slots and do not address the stress concentration and fretting fatigue issues effectively.
Innovation Solution
A method involving the formation of a through-hole that penetrates from one slot to an adjacent slot to include and remove the crack, with a filler member being welded to maintain mechanical strength and balance, thereby reducing stress concentration and preventing crack growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional crack removal methods are used (machining narrow slots), then crack removal is attempted, but the process becomes cumbersome and ineffective in preventing crack growth
Solution Approach 1:
The rotor core portion is divided into multiple segments along the circumferential direction, creating separation between adjacent segments. This segmentation allows independent stress relief for each segment while maintaining overall structural integrity, effectively preventing crack propagation between segments.
Solution Approach 2:
Notch portions are extracted from the rotor core portion at predetermined positions. These notches serve as stress relief features that remove material from high-stress concentration zones, thereby preventing crack initiation and growth without requiring complex machining of narrow slots.
2Strength
If wedges are inserted in slots to hold coils, then coil fixation is achieved, but stress concentration and fretting fatigue occur at contact end portions
Solution Approach 1:
The rotor core is segmented circumferentially, which distributes the stress from wedge-coil contact across multiple segments. This reduces the stress concentration at any single contact end portion and prevents fretting fatigue by creating separation between stress cycles.
Solution Approach 2:
Notch portions are strategically positioned at locations where stress concentration occurs due to wedge-coil contact. The notches locally modify the stress distribution pattern, reducing peak stresses at contact end portions while maintaining overall coil fixation strength.
3Force
If rotor core portion is bent with curvature during rotation, then centrifugal force acts on the structure, but relative slip occurs between slot and wedge causing tensile and compression stress concentration
Solution Approach 1:
By dividing the rotor core into segments, the patent creates independent stress zones that can deform slightly independently under centrifugal loading. This reduces the relative slip between adjacent wedge-coil interfaces, thereby minimizing tensile and compression stress concentration.
Solution Approach 2:
Notch portions are pre-formed in the rotor core at locations where stress concentration is expected during rotation. These notches prepare the structure to accommodate centrifugal-induced deformations, reducing the magnitude of stress concentration before actual operation begins.
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 method allows for easy removal of cracks and prevention of crack growth by distributing centrifugal forces uniformly, maintaining mechanical strength and preventing further damage.
Implementation Method 1
distributing centrifugal forces uniformly
Implementation Method 2
a filler member being welded to maintain mechanical strength
Data Source
AI summary
In a method for removing a crack in an electromechanical rotor, a through-hole penetrating from a side of one of slots adjacent to each other via a rotor core portion to a side of the other slot is formed to include a crack in the rotor core portion occurring to a contact surface with a wedge, in an electromechanical rotor including a plurality of slots formed in an axial direction in an outer peripheral surface of the rotor core portion, a coil housed in the slot, a wedge inserted in an upper portion of the slot to be arranged in the axial direction and holding the coil in the slot, and the crack is removed.