Cage Rotor Conductor Bar Fixation by Local Annealing and Compression
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Solution Overview
Problem
Cage rotors of asynchronous machines face challenges in preventing conductor bar oscillations during high rotational speeds, which can impair machine operation and require high manufacturing efforts due to tight fit size tolerances.
Innovation Solution
The solution involves using conductor bars with sections of lower hardness, specifically soft-annealed, which are axially inserted into slots with a clearance fit. Compression of these softer sections creates abutment points within the slots, preventing conductor bar oscillations and ensuring secure fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductor bars are inserted with narrow fit size tolerance to prevent oscillation, then reliability is improved, but manufacturing time increases and productivity decreases
Solution Approach 1:
The patent changes the physical state of the conductor bar by annealing specific sections to reduce hardness and increase plasticity. This parameter change allows the conductor bar to be compressed and deformed into the slot, creating a secure fit that prevents oscillation during operation while enabling faster installation compared to precision fitting methods
2Reliability
If conductor bars are driven axially into slots with narrow tolerance, then oscillation is prevented, but manufacturing effort and complexity increase
Solution Approach 1:
The conductor bar sections are annealed to change their mechanical properties, making them softer and more formable. This allows a simpler compression and deformation process to achieve secure fixation, replacing complex precision fitting or additional fastening mechanisms
Solution Approach 2:
Only specific sections of the conductor bar are annealed rather than the entire bar. This local quality change applies the softening treatment precisely where needed for insertion and fixation, while maintaining the original properties of other sections
3Productivity
If conductor bars are inserted with clearance fit for easy insertion, then productivity improves, but conductor bar oscillation occurs during operation
Solution Approach 1:
The annealing process changes the physical parameters of the conductor bar sections, making them sufficiently soft to be compressed into clearance fits easily, yet capable of being deformed to create secure abutment points that prevent oscillation during operation
Solution Approach 2:
The annealing is performed in advance on specific sections of the conductor bar before insertion. This preliminary softening action enables easy insertion with clearance fit while ensuring that the soft sections can subsequently be compressed to create secure fixation, preventing oscillation
4Reliability
If copper bars are used to increase efficiency, then electrical conductance improves, but manufacturing effort increases due to narrow tolerance requirements
Solution Approach 1:
The annealing process modifies the physical state of the copper conductor bar sections, making them softer and more pliable. This allows copper bars to be easily inserted into slots with clearance fit and securely fixed through compression, eliminating the time-consuming precision fitting normally required for copper bars while maintaining their high electrical efficiency
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 approach effectively prevents conductor bar oscillations across a wide rotational speed range, enhances copper fill factor, simplifies production, and allows for automated manufacturing, thereby improving the operational reliability and efficiency of asynchronous machines.
Implementation Method 1
conductor bars which at specified sections in its longitudinal extension has a lower hardness, in particular is soft-annealed
Implementation Method 2
axial compression of the conductor bars inside the respective slot, so abutment points defined in the axial course of the slot are formed between the conductor bar and the inside of the slot
Data Source
AI summary
A conductor bar of a cage rotor of an asynchronous machine has a longitudinal extension and includes first and second sections in the longitudinal extension. The first section has a hardness which is lower than a hardness of the second section and is realized through soft annealing, brief inductive heating or heating by a flame so as to enable a compression of the first section of the conductor bar by way of axial pressure after axially joining the conductor bar in a slot of a magnetically conductive body of the cage rotor, with the first section abutting an inner wall of the slot of magnetically conductive body of the cage rotor.