External Rotor Motor Cooling Wheel for Directed Stator Airflow
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Solution Overview
Problem
Existing external rotor motors suffer from inefficient cooling methods, leading to suboptimal power density due to undefined air flow and heat dissipation.
Innovation Solution
An external rotor motor design featuring a cooling wheel that generates a directed air flow through the stator, utilizing an overpressure and negative pressure zones to cool the stator efficiently, with blades positioned adjacent to the stator to prevent direct air flow reversal and enhance heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an undefined air flow is used for cooling the stator, then the cooling system is simple, but the heat dissipation efficiency is low
Solution Approach 1:
The cooling system is segmented into distinct functional zones: an outer portion with fluid inlet and an inner portion with fluid outlet, separated by a radially extending partition. This segmentation allows independent optimization of each zone's cooling characteristics while maintaining overall system efficiency.
Solution Approach 2:
The patent introduces a radial dimension to the air flow path by creating a directed flow from the outer diameter through the stator to the inner diameter. This radial flow pattern, enforced by the partition and pressure differential, transforms the cooling approach from undefined three-dimensional convection to a controlled two-dimensional flow path, significantly improving heat dissipation efficiency.
2Temperature
If the cooling wheel is positioned close to the stator, then the cooling efficiency is improved, but the risk of direct air flow reversal increases
Solution Approach 1:
The partition is positioned preliminarily to prevent air flow reversal before it can occur. By creating a physical barrier that extends radially from the stator, the system preemptively blocks any potential reverse flow path, ensuring that air must travel through the intended cooling path from outer to inner diameter.
Solution Approach 2:
The partition acts as an intermediary element between the outer and inner portions of the stator. It mediates the air flow by forcing it to pass through the stator core rather than allowing direct communication between the outer and inner spaces, thus preventing reverse flow while maintaining cooling efficiency.
3Power
If the stator is cooled more effectively, then the power density increases, but the device complexity increases
Solution Approach 1:
The cooling wheel serves multiple functions simultaneously: it generates the pressure differential needed for directed air flow, it acts as a structural support element, and it facilitates heat transfer from the stator. This multi-functionality allows effective cooling and high power density without proportionally increasing device complexity.
Solution Approach 2:
The cooling system is designed to be self-sufficient, using the rotation of the cooling wheel itself to generate the necessary pressure differential for air flow. The system does not require external fans or pumps, as the cooling wheel's rotation naturally creates the overpressure at the outer diameter and negative pressure at the inner diameter, enabling self-driven 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
The solution achieves enhanced cooling and higher power density by ensuring a defined and efficient air flow that effectively dissipates heat from the stator, improving motor performance.
Implementation Method 1
The cooling wheel generates an overpressure, on an outer diameter of the cooling wheel adjacent to the outer portion of the stator, and a negative pressure, on an inner diameter of the cooling wheel adjacent to the inner portion of the stator
Implementation Method 2
a directed air flow is generated flowing from the outer diameter of the cooling wheel through the outer portion and the inner portion to the inner diameter of the cooling wheel
Data Source
AI summary
An external rotor motor (1) has a stator (10), a rotor (20) and a cooling wheel (30) that rotates with the rotor (20) and the stator (10) to cool the stator (10). The stator (10) has an inner portion (11), enabling fluid flow, and a surrounding outer portion (12) enabling fluid flow. The flow is fluidically separate from the inner portion (11) in the radial direction (X). The cooling wheel (30) has a plurality of blades (33) to generate an overpressure and a negative pressure. The cooling wheel (30) generates a directed air flow (L) flowing from the outer diameter (32) of the cooling wheel (30) through the outer portion (12) and the inner portion (11) to the inner diameter (31) of the cooling wheel (30).