Stator Cooling Element Conical Contact for Outer Rotor Machines
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Solution Overview
Problem
The mechanical contact between the cooling element and the yoke in outer rotor electrical machines loosens due to thermal expansion, increasing heat resistance and impairing cooling efficiency, unlike inner rotor machines.
Innovation Solution
A stator design with conical surfaces for the cooling element and yoke cavity, allowing mechanical contact facilitated by tensioning devices like screws and springs to maintain heat conduction, preventing loosening during cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a cooling element is mechanically contacted with the yoke to conduct heat, then heat conduction efficiency is improved, but the mechanical contact loosens due to thermal expansion when cooled, increasing heat resistance and impairing cooling
Solution Approach 1:
The patent applies conical surfaces (curved geometry) to the contact interfaces between the cooling element and yoke. The conical shape allows for self-adjusting contact under thermal expansion and contraction, maintaining continuous mechanical contact and heat conduction path despite temperature changes. The curved surface geometry accommodates dimensional changes while preserving the heat transfer connection.
Solution Approach 2:
The patent changes the geometric parameters of the contact surfaces from flat to conical, and utilizes tensioning devices that can adjust their tensioning force. This parameter adjustment allows the system to compensate for thermal expansion variations, maintaining optimal contact pressure and heat conduction efficiency across different operating temperatures.
2Power
If linear current density is increased to increase maximum torque, then torque output is improved, but resistive losses in the stator winding increase, requiring enhanced cooling
Solution Approach 1:
The patent introduces a cooling element as an intermediary component between the stator windings and the external cooling system. This cooling element provides a dedicated heat transfer path that efficiently removes resistive losses from the windings, enabling higher current densities to be sustained without excessive temperature rise. The cooling element acts as a thermal mediator that decouples the power generation function from the thermal management challenge.
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 design maintains effective heat conduction and cooling efficiency by ensuring a stable mechanical contact between the cooling element and yoke, even under temperature changes, thus enhancing the performance of outer rotor electrical machines.
Implementation Method 1
a cooling element located in a cavity constituted by the yoke and being in a heat conductive relation with the yoke
Implementation Method 2
the mechanical contact between the cooling element and the yoke tends to loosen when the cooling element is cooled because cooling decreases the dimensions of the cooling element in accordance with the thermal expansion coefficient of the material of the cooling element
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
A stator (100) for an outer rotor electrical machine comprises stator windings (103) and a core structure (101) comprising ferromagnetic material. The core structure comprises a yoke (102) and stator teeth connected to the yoke. The stator comprises a cooling element (104) located in a cavity constituted by the yoke and being in a heat conductive relation with the yoke. A surface of the cooling element has a mechanical contact with a surface of the cavity so as to provide the heat conductive relation. The mutually contacting surfaces of the cooling element and the cavity are conical so as to facilitate arranging the mechanical contact between the yoke and the cooling element. The conical shapes of the surfaces make it possible to maintain the heat conductive relation with the aid of tensioning devices, e.g. screws and/or springs, for generating axial force pressing the cooling element axially against the yoke.