Asynchronous Machine Rotor Skewing via Twisting
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Solution Overview
Problem
Existing methods for producing high-power asynchronous machine rotors are costly and prone to quality variability due to pressure diecasting, and require labor-intensive soldering or welding for short-circuiting rings, which are inefficient and not suitable for automated manufacturing.
Innovation Solution
A method involving a laminated rotor core with parallel slots and conductor rods that are twisted using a tool to create a skewed cage winding, allowing for the use of pre-prepared short-circuiting rings pressed onto the core without bending, and achieving stability through hot forming of short-circuiting disks at specific temperature and deformation rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pressure diecasting is used to produce squirrel-cage rotors, then production efficiency is improved, but manufacturing precision and quality consistency deteriorate due to melt variability, impurities, and casting defects
Solution Approach 1:
The rotor is divided into separate components: laminated rotor core, conductor rods, and short-circuiting rings. These components are manufactured independently with high precision and then assembled, eliminating the quality variability inherent in one-step pressure diecasting while maintaining production efficiency.
Solution Approach 2:
Multiple high-precision manufacturing processes (laminating, rod insertion, compression molding) are combined into an integrated assembly process that achieves both high productivity and high manufacturing precision, overcoming the trade-off present in traditional pressure diecasting.
2Strength
If soldering or welding is used to connect conductor bars to short-circuiting rings, then mechanical strength is improved, but device complexity and production cost increase due to additional operations and material requirements
Solution Approach 1:
The chemical/thermal joining processes (soldering, welding) are replaced with a purely mechanical compression molding process. The conductor rods and short-circuiting rings are mechanically pressed together with sufficient force to create stable electrical and mechanical connections, eliminating the need for additional materials and complex thermal processes.
Solution Approach 2:
The complex soldering or welding operations are extracted from the manufacturing process and replaced with simple compression molding. This removes the harmful factors associated with thermal processes while maintaining connection strength.
3Adaptability or versatility
If rotor bars are bent to create skewed cage windings, then starting characteristics are improved, but manufacturing precision deteriorates due to additional bending operations and alignment requirements
Solution Approach 1:
The skew angle is predetermined and built into the compression molding process itself. The molding tooling is designed with the specific skew geometry, allowing the rotor bars to be formed with the correct skew angle in a single operation, eliminating the need for separate bending operations and maintaining high manufacturing precision.
Solution Approach 2:
The skew angle parameter is integrated into the compression molding process parameters. By adjusting the molding tool geometry and compression conditions, the desired skew angle is achieved directly during assembly, rather than requiring post-assembly bending operations that compromise precision.
4Reliability
If short-circuiting rings with circumferential solder tanks are used, then connection stability is improved, but loss of substance increases due to high silver content in solder
Solution Approach 1:
The soldering process using silver-based materials is replaced with a mechanical compression process. The short-circuiting rings are pressed directly onto the conductor rods with sufficient force to create stable electrical connections without requiring any solder or additional materials, eliminating silver consumption entirely.
Solution Approach 2:
The expensive silver solder is eliminated in favor of a reusable compression molding process. The connection is achieved through mechanical pressure alone, making the process economically sustainable without consuming valuable materials.
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 eliminates the need for pressure casting, soldering, or welding, enabling automated manufacturing of stable skewed rotors with improved starting characteristics and reduced torque undulation, magnetic eddying, and vibratory forces, while using materials like aluminum or copper for enhanced performance.
Implementation Method 1
achieving stability through hot forming of short-circuiting disks at specific temperature and deformation rates
Data Source
AI summary
A method for producing a rotor of an asynchronous machine includes providing a rotor lamination stack having grooves extending parallel to a rotor axis of the rotor, inserting conductor rods into the grooves such that the conductor rods protrude from end faces of the rotor lamination stack, wherein a twisting tool is placed at each of the end faces onto the protruding conductor rods and the twisting tools are twisted relative to each other, where the parallel grooves with the corresponding conductor rods also extend obliquely after the twisting and where the twisting tools are formed such that the protruding conductor rods remain parallel to the rotor axis when an oblique profile of the stack is produced, removing the twisting tools, providing first and second short-circuit washers, and axially pressing the short-circuit washers onto the conductor rods projecting perpendicularly from the end face of the rotor lamination stack.