Squirrel-Cage Rotor Copper Fill Factor and Casting
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Solution Overview
Problem
Hybrid squirrel-cage rotors in dynamoelectric machines have limitations in electrical, thermal, and mechanical design due to their lower energy efficiency compared to pure copper rotors, and their manufacturing process restricts the copper fill factor and prevents the realization of stray webs, leading to unreliable cooling and mechanical fixation issues, especially at high speeds and load changes.
Innovation Solution
A squirrel-cage rotor design where a copper conductor is inserted and fixed in a recessed groove with adjustable slot dimensions, allowing for a high copper fill factor and improved cooling through caulking, and the use of separate short-circuit rings formed by pouring channels for aluminum, ensuring reliable mechanical fixation and adjustable starting behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the slot cross-section is partially occupied by copper insert rod to allow aluminum casting flow, then the manufacturing process is feasible, but the copper fill factor is reduced and electrical efficiency deteriorates
Solution Approach 1:
The slot is divided into two functional zones: an upper casting channel zone that allows aluminum flow, and a lower conductor zone that is fully occupied by copper insert rods. This segmentation enables both adequate copper fill factor for electrical efficiency and sufficient space for casting process
Solution Approach 2:
A groove structure is introduced as an intermediary element between the copper insert rod and the aluminum casting material. The groove provides a dedicated channel for aluminum flow while allowing the copper insert rod to occupy the full cross-section of the slot for optimal electrical performance
2Reliability
If the laminated core is closed in circumferential direction to prevent aluminum escape, then manufacturing safety is improved, but stray webs cannot be realized and electrical design is limited
Solution Approach 1:
The laminated core structure is made locally adaptive: in regions where stray webs are required for specific electrical characteristics, the core remains open to allow aluminum flow and create stray web structures, while in other regions the core is closed to prevent aluminum escape. This local differentiation enables both manufacturing reliability and electrical design flexibility
3Ease of manufacture
If conductor bar is cooled only by punctiform bearing on slot walls, then manufacturing is simplified, but cooling efficiency is insufficient and thermal management deteriorates
Solution Approach 1:
The cooling function is merged with the structural support function by integrating cooling channels directly into the slot walls that contain the conductor bars. The slot walls serve dual purposes: mechanical support for the conductor and heat dissipation pathway through integrated cooling channels
4Ease of manufacture
If copper insert rod is not mechanically fixed in groove and center of laminated core, then manufacturing is simpler, but mechanical stability is insufficient and snaking occurs at high speeds
Solution Approach 1:
The copper insert rod is preliminarily positioned and mechanically fixed in the groove and center of the laminated core before the aluminum casting process. This preliminary fixation ensures proper alignment and prevents snaking at high speeds, while the subsequent aluminum casting provides additional mechanical anchoring
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 the electrical efficiency, starting behavior, and mechanical stability of the dynamoelectric machine by allowing for a high copper fill factor, improved cooling, and secure conductor fixation, preventing 'snaking' at high speeds and load changes, while maintaining efficient heat dissipation.
Implementation Method 1
which are formed using tools provided for this purpose and, if necessary, other special second recesses in the magnetically conductive base body of the squirrel cage rotor, in particular using pouring channels that transport a second electrically conductive material from one side of the conductive base body to the other side in a liquid state
Implementation Method 2
A conductor made of a first electrically conductive material in a predetermined shape, in particular a conductor rod made of copper, is now inserted and/or fixed axially in a first recess of the magnetically conductive base body
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a squirrel-cage rotor (9) of a dynamo-electric machine (1) comprising: - a magnetically conductive base body, in particular a laminated core (32), which extends from one axial end to a second axial end along an axis (4), with substantially axially extending first recesses (28) which are designed as slots (33) and are located on the radially outer edge of the lateral surface of the magnetically conductive base body and which have only a first conductor material (34); - a short-circuit ring (10), each at the axial ends of the magnetically conductive base body, which has at least a second electrically conductive material (35) and which surrounds the axis (4), wherein the first electrically conductive material (34) of the slots (33) is electrically contacted with the second electrically conductive material (35) at the axial ends.