Cooled Rotor Heat Pipe Integration for Asynchronous Machines
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Solution Overview
Problem
Existing squirrel-cage rotors for asynchronous machines face challenges in heat dissipation, particularly in machines with higher pole numbers and longer axial lengths, where conventional cooling methods are less effective due to reduced heat dissipation through short-circuit rings.
Innovation Solution
The integration of heat pipes, which are cast directly onto short-circuit rings, enhances heat dissipation by creating an effective heat conduction and convection cycle, with copper heat pipes and aluminum short-circuit rings optimized for thermal and mechanical contact through alloy layers, and strategically arranged slots for improved electrical efficiency and starting torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional cooling methods with vanes on short-circuit rings are used, then heat dissipation is achieved at high speeds, but heat dissipation effectiveness is reduced in machines with higher pole numbers and longer axial lengths
Solution Approach 1:
The rotor core is divided into multiple segments with individual cooling channels distributed throughout its length. This segmentation allows heat to be removed from different axial positions independently, making the cooling system effective for rotors with higher pole numbers and longer axial lengths where conventional single-point cooling fails
Solution Approach 2:
A cooling medium (liquid or gas) is introduced as an intermediary substance that absorbs heat from the rotor core through the cooling channels and transports it to external heat exchangers. This mediator enables heat dissipation without relying solely on the rotor's rotational speed, thus maintaining effectiveness across different machine configurations
2Temperature
If short-circuit rings are made of copper for high thermal conductivity, then heat dissipation is improved, but the mass moment of inertia of the rotor increases significantly
Solution Approach 1:
The short-circuit rings are constructed using composite material structures, combining aluminum (for low weight and acceptable conductivity) with strategically placed copper elements or high-conductivity coatings only in critical heat transfer zones. This composite approach achieves adequate heat dissipation while maintaining low mass moment of inertia
Solution Approach 2:
Instead of making the entire short-circuit ring from high-conductivity copper, the patent applies high thermal conductivity materials only in specific local zones where heat transfer is most critical, such as at the interfaces with cooling channels or at the outer periphery, while using lighter materials in other regions
3Weight of moving object
If aluminum short-circuit rings are used to reduce mass moment of inertia, then rotational performance is improved, but thermal conductivity and heat dissipation capability are reduced compared to copper
Solution Approach 1:
The patent introduces active cooling channels as an intermediary heat removal system that compensates for aluminum's lower thermal conductivity. The cooling medium directly contacts the short-circuit rings through these channels, providing an alternative heat transfer path that bypasses the limitation of aluminum's material properties
Solution Approach 2:
The patent modifies the thermal parameters of the aluminum short-circuit rings by incorporating high-conductivity coatings, embedded heat pipes, or phase-change materials that enhance heat transfer capability without significantly increasing mass, thus improving heat dissipation while maintaining low moment of inertia
4Temperature
If heat pipes are integrated into the rotor core for heat dissipation, then heat transfer is improved, but the complexity of the manufacturing process increases
Solution Approach 1:
The manufacturing process merges the heat pipe integration with the existing rotor core fabrication steps. Heat pipes are inserted into pre-formed channels during the same casting or assembly process used for creating the rotor core and short-circuit rings, eliminating the need for separate post-manufacturing installation steps and reducing overall complexity
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 solution significantly improves heat dissipation and electrical efficiency of the squirrel-cage rotor, reducing electrical contact resistance and mechanical stress, while also enhancing starting behavior and overall performance compared to conventional designs.
Implementation Method 1
The heat pipes, which can be thermosiphons or heat pipes, penetrate the laminated rotor core essentially axially. They transport the heat generated in the rotor core to the two front ends of the rotor.
Implementation Method 2
The heat pipes, which can be thermosiphons or heat pipes, penetrate the laminated rotor core essentially axially.
Implementation Method 3
an alloy layer being formed on the heat pipes in the zones in which they are arranged within the short-circuit rings, which alloy layer is applied in particular galvanically
Implementation Method 4
The part of the heat pipes protruding from the short-circuit rings thereby assumes the function of fan blades and thus supports convection.
Data Source
Figure 1~4
Figure 5~6
Figure 7~8
AI summary
The invention relates to a squirrel-cage rotor for an asynchronous machine (7), wherein the squirrel-cage rotor comprises: a rotor lamination stack (1), short-circuit bars (2) arranged within the rotor lamination stack (1), and short-circuit rings (3) cast onto the rotor lamination stack (1), which electrically connect the short-circuit bars (1) to each other at the end faces of the rotor lamination stack (1). To improve heat dissipation, heat tubes (4) are inserted axially into the rotor lamination stack (1), projecting out of the rotor lamination stack (1) at the end faces and into the short-circuit rings (3).