Permanent Magnet Rotor Thermal Management via Conductive Bars
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Solution Overview
Problem
Cooling permanent magnets in electric machine rotors is challenging, leading to degradation and demagnetization at elevated temperatures, which can result in motor failure.
Innovation Solution
Incorporating thermally-conductive bars in the gaps between the rotor magnets and the rotor core openings to transfer thermal energy from the interior of the rotor to the axial ends, where it can be dissipated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If permanent magnets are placed in oval slots with gaps filled by nylon or epoxy, then the magnetic structure is stable, but the magnets overheat leading to degradation and demagnetization
Solution Approach 1:
The patent changes the thermal parameter of the gap filling material from insulating (nylon, epoxy) to highly conductive (aluminum, copper, graphite). This parameter change transforms the thermal behavior of the system, allowing heat to be conducted away from the magnets rather than trapped, thus resolving the overheating problem while maintaining structural stability
Solution Approach 2:
The patent introduces thermally-conductive bars as intermediary elements between the permanent magnets and the rotor core/external cooling system. These bars act as thermal mediators that facilitate heat transfer from the magnets through the gap region to the rotor core, enabling effective cooling while preserving the magnetic structure
2Temperature
If thermally-conductive bars are added to cool the magnets, then the cooling effectiveness improves, but the device complexity increases
Solution Approach 1:
The patent merges the cooling function with the existing gap region between the magnets and rotor core. Instead of adding separate cooling systems, the thermally-conductive bars utilize the existing gap space, combining the structural gap with the thermal management function. This reduces the need for additional components and simplifies the overall rotor structure
Solution Approach 2:
The thermally-conductive bars serve multiple functions: they provide thermal conduction pathways for cooling, maintain the magnetic gap spacing, and can be integrated with the rotor core structure. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while achieving effective cooling
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
Effectively cools the rotor magnets, preventing degradation and demagnetization, thereby enhancing the reliability and performance of the electric machine by efficiently managing thermal energy.
Implementation Method 1
One or more thermally-conductive bars are located in the one or more gaps to transfer thermal energy from an interior of the rotor assembly toward an axial end of the rotor assembly
Data Source
AI summary
A permanent magnet rotor assembly for an electric machine includes a rotor core including one or more axially-extending openings and one or more permanent magnets located in the one or more axially-extending openings defining one or more gaps between the one or more permanent magnets and the one or more axially-extending openings. One or more thermally-conductive bars are located in the one or more gaps to transfer thermal energy from an interior of the rotor assembly toward an axial end of the rotor assembly.