Cast-in-place induction rotor end rings with interlocks
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Solution Overview
Problem
Existing induction motor rotor fabrication methods often result in oxide inclusions and voids in conductor bars and shorting end rings, reducing power density due to turbulent molten material flow and hot tearing, which complicates the manufacturing process, especially when using copper materials.
Innovation Solution
A rotor core design featuring a cylindrically shaped steel laminate stack with radially-oriented grooves for conductor bars and a retention feature on the end sheet to securely attach the shorting end ring, using copper-based materials for improved conductivity and heat transfer, and interlocking features to prevent separation under centrifugal forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If copper material is used for conductor bars and shorting end rings, then power density and heat transfer characteristics are improved, but manufacturing process time and complexity increase
Solution Approach 1:
The rotor is divided into a laminated steel stack and separately manufactured copper end rings. The end rings are pre-formed with grooves that mate with conductor bars, allowing independent fabrication and assembly. This segmentation enables use of copper for improved power density while simplifying the manufacturing process through modular assembly rather than complex in-situ casting.
Solution Approach 2:
The copper end rings are pre-manufactured with integrated grooves for conductor bars before assembly to the laminated stack. This preliminary formation of the end rings with their structural features eliminates the need for complex turbulent casting operations during final assembly, reducing manufacturing time while maintaining the power density benefits of copper material.
2Temperature
If copper material is used for conductor bars and shorting end rings, then heat transfer characteristics are improved, but device complexity increases
Solution Approach 1:
The shorting end ring and conductor bar support structure are merged into a single integrated copper component. The end ring includes built-in grooves that accommodate conductor bars, eliminating the need for separate support structures or complex assembly operations. This merging maintains superior heat transfer characteristics of copper while reducing overall device complexity through integration.
Solution Approach 2:
The copper shorting end ring serves multiple functions simultaneously: it provides electrical shorting for the conductor bars, acts as a structural support component, provides heat sinking for thermal management, and includes integrated grooves for conductor bar positioning. This multi-functionality reduces the number of separate components needed, thereby reducing device complexity while maintaining excellent heat transfer characteristics.
3Ease of manufacture
If molten material is introduced into conductor bar grooves during casting, then conductor bars and shorting end rings are formed in place, but oxide inclusions and voids are created
Solution Approach 1:
The manufacturing process is segmented into separate steps: end rings are pre-cast with grooves, then conductor bars are inserted into these pre-formed grooves during assembly. This segmentation avoids the need for turbulent in-situ casting of conductor bars, eliminating oxide inclusions and voids while maintaining ease of manufacture through modular assembly. The pre-formed grooves provide precise positioning without requiring complex simultaneous casting operations.
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 design enhances power density and electrical conductivity by minimizing voids and oxide inclusions, simplifying the manufacturing process, and maintaining structural integrity under stress conditions.
Implementation Method 1
An electric-powered induction motor transforms electric power to mechanical torque by inducing rotating magnetic fields between a static element, i.e., a stator, and a rotatable element, i.e., a rotor.
Implementation Method 2
The conductor bars are each located in one of the plurality of longitudinal grooves and each includes a first end projecting from a first end of the steel laminate stack
Implementation Method 3
The use of copper material for conductor bars and/or shorting end rings may increase power density and heat transfer characteristics of an induction motor
Data Source
AI summary
An induction motor has a rotor core including a plurality of conductor bars and a shorting end ring having a plurality of grooves aligned with and mated to the first ends of the conductor bars. The rotor core further includes a cylindrically shaped steel laminate stack including a plurality of longitudinal grooves distributed around the periphery of the steel laminate stack. The conductor bars are each located in one of the plurality of longitudinal grooves and each includes a first end projecting from a first end of the steel laminate stack. The rotor core further includes an end sheet located to the end of the steel laminate stack, the end sheet including a retention feature configured to retain the shorting end ring to the end sheet.