Squirrel Cage Rotor Micro-Welding and Hot Forming
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Solution Overview
Problem
The production of squirrel-cage rotors for asynchronous machines is cost-intensive and prone to quality variations due to die-casting limitations, especially in higher performance ranges, where the connection between conductor bars and short-circuit rings is inefficient and economically unfavorable.
Innovation Solution
A method combining micro-welding and hot forming to connect conductor bars with short-circuit ring disks, where conductor bars are inserted into a rotor stack, held in place, and then axially pressed against aluminum or aluminum alloy short-circuit rings, forming a micro-weld for a strong and efficient connection, with subsequent heat treatment to enhance mechanical and electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If die-casting technology is used to produce squirrel-cage rotors, then production is consolidated into a single operation, but production costs increase due to expensive and quickly wearing die-cast molds
Solution Approach 1:
The production process is divided into separate operations: conductor bars are inserted into rotor laminations first, then short-circuit rings are separately pressed and welded onto the conductor bars. This segmentation eliminates the need for expensive die-cast molds while maintaining production efficiency.
Solution Approach 2:
The connection of conductor bars to short-circuit rings is achieved by merging pressing and micro-welding operations into a single integrated process step, reducing the number of separate manufacturing operations needed while lowering tooling costs.
2Productivity
If die-casting technology is used to produce squirrel-cage rotors, then production is consolidated into a single operation, but quality scatter increases due to melt contamination and casting defects
Solution Approach 1:
By separating the production into distinct steps (insertion, pressing, welding), each operation can be optimized and controlled independently, eliminating the quality issues associated with die-casting such as melt contamination and cavity formation while maintaining high productivity.
3Strength
If soldering or welding processes are used to connect conductor bars with short-circuit rings in higher performance range, then connection strength is improved, but production cost increases due to high proportion of silver in solder
Solution Approach 1:
The invention replaces expensive silver-based solder with a cost-effective micro-welding process that creates strong connections without requiring valuable materials. The micro-welding produces durable connections suitable for high-performance applications while eliminating the need for costly solder.
4Manufacturing precision
If pressure die-casting process is carried out under protective gas with additional measures, then quality losses are reduced, but additional measures are necessary for strength such as support rings or high-strength alloys
Solution Approach 1:
The invention eliminates the need for protective gas environments and additional strengthening measures by using a segmented production process with micro-welding. The separate pressing and welding operations create inherently strong connections without requiring complex protective atmospheres or high-strength alloy materials.
Solution Approach 2:
The invention replaces the complex die-casting mechanical system with a simpler combination of insertion, pressing, and micro-welding operations. This substitution eliminates the need for support rings and high-strength alloys while achieving superior connection quality and strength.
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 reduces production costs, eliminates casting defects, and provides a robust, efficient connection suitable for high-speed applications with improved mechanical strength and electrical conductivity, enhancing the performance and reliability of squirrel-cage rotors.
Implementation Method 1
This is done by axially pressing the short-circuit ring disk onto the conductor bars or the conductor bars onto the short-circuit ring disk or mutual axial pressing, with the conductor bar/conductor bars and short-circuit ring disk moving towards one another. This axial pressing is done taking into account the ideal temperature range for deformation and the optimal rate of deformation. A plastic deformation takes place through dislocation migration of the atomic planes in the lattice.
Implementation Method 2
A micro-weld is formed between the material of the annular short-circuit ring and the conductor bars. This micro-weld is created by the fact that the conductor bar and the short-circuit ring rub against each other and thus generate surface pressure and additional frictional heat. The permissible shear stresses of these materials are locally exceeded and mass transfers are caused by diffusion at the interface between the conductor bar and the short-circuit ring.
Implementation Method 3
subsequent heat treatment to enhance mechanical and electrical properties
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a method for producing a squirrel-cage rotor (4) for an asynchronous machine (1) comprising the following steps: - providing a laminated rotor core (5) having substantially axially running grooves (14), - inserting into the grooves (14) conductor rods (6) made from a first conductive material in such a manner that the conductor rods (6) protrude from the end faces (15) of the laminated rotor core (5), - providing a short circuit ring disc (7) made from a second conductive material, which is heated above the recrystallization temperature, - axially pressing in at least one short circuit ring disc (7) from the end face (15) of the laminated rotor core (5) with protruding conductor rods (6) taking into account the temperature range of deformation and the rate of deformation, - subsequently or simultaneously hot shaping the short circuit ring disc (7) which has been axially pressed on.