Cage Rotor Conductor Bars with Annealed Sections for Vibration Control
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Solution Overview
Problem
Squirrel cage rotors in asynchronous machines face challenges with conductor bar oscillation and inefficient copper filling, leading to long production times, potential metal chip formation, and reduced operational reliability, especially at high speeds and torque applications.
Innovation Solution
Conductor bars with sections of lower hardness are achieved through soft annealing or brief inductive heating, allowing for axial compression and creation of defined contact points within the grooves, which prevents oscillation and ensures a high copper filling factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductor bars are inserted with tight tolerances to prevent vibration, then vibration prevention is improved, but manufacturing time increases due to lengthy insertion processes
Solution Approach 1:
The conductor bars are pre-annealed at specific sections before insertion to reduce hardness and facilitate easier insertion. This preliminary softening action enables the bars to be inserted without excessive force while still achieving secure fixation, thereby reducing manufacturing time without compromising vibration prevention
Solution Approach 2:
Only specific sections of the conductor bars (the insertion ends) are annealed to reduce hardness, while the remaining portions maintain their original hardness. This localized quality change allows easy insertion at the annealed sections while preserving the mechanical strength and vibration resistance of the unannealed sections
2Reliability
If conductor bars are hammered in with force to ensure secure fixation, then fixation reliability is improved, but metal shavings are produced that can block or impair operation
Solution Approach 1:
The hardness parameter of the conductor bar insertion sections is changed through annealing, reducing it from a hard state to a softer state. This parameter change enables the bars to be inserted with minimal force, preventing the generation of metal shavings while still achieving reliable fixation through the controlled deformation of the softened material
3Ease of manufacture
If clearance fit is used for easy insertion, then ease of manufacture is improved, but conductor bars vibrate during operation due to gaps
Solution Approach 1:
The conductor bars are pre-annealed at the insertion sections to create a temporary soft state that facilitates easy insertion with clearance fit. After insertion, the bars are mechanically deformed (upset) to create interference fit, transforming the clearance fit advantage into a reliable vibration-free operation state
4Reliability
If copper rods are used for high electrical conductivity, then electrical conductivity is improved, but slot filling is incomplete requiring additional materials
Solution Approach 1:
The conductor bars are designed with localized annealed sections only at the insertion ends, while the main body portions maintain their high electrical conductivity without annealing. This local quality differentiation allows the bars to be easily inserted while preserving the electrical conductivity required for high-performance operation
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
The solution effectively reduces conductor bar oscillations, simplifies production, and enhances the asynchronous machine's performance across a wide speed range and torque applications by ensuring secure conductor bar fixation without compromising rotor strength.
Implementation Method 1
This is achieved by annealing, brief inductive heating, or heating with a flame at these points on the conductor bar
Implementation Method 2
brief inductive heating
Implementation Method 3
heating with a flame
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a conductor rod (9) of a cage rotor (8) of an asynchronous machine (5), said conductor rod having in its longitudinal extension at predefined sections (11) a lower hardness and is in particular soft-annealed.