Electric Motor Cooling Structure Using Internal Air Bypass
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Solution Overview
Problem
Existing electric motors, particularly those used in railway vehicles, face inefficiencies in cooling performance due to the use of internal air, which is less effective than external air, and increasing airflow rate to enhance cooling leads to windage losses, reducing motor efficiency.
Innovation Solution
The electric motor design incorporates a shaft, rotor, stator, brackets, and guides with partition walls that facilitate the transfer of heat from internal air to external air, using tubular structures to guide and cool the air without increasing fan size, thereby enhancing cooling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the fan size is increased to increase the airflow rate for better cooling, then the cooling performance is improved, but the windage loss increases, thus lowering the motor efficiency
Solution Approach 1:
The cooling system is segmented into two independent pathways: external air cooling for the stator and internal air cooling for the rotor. This segmentation allows each component to be cooled by the most suitable air source without requiring a single large fan that would cause excessive windage losses.
Solution Approach 2:
A heat exchanger is introduced as an intermediary device that transfers heat from the internal air (which has absorbed heat from the rotor) to the external air. This mediator enables the internal air cooling system to function effectively without requiring the internal air to be directly discharged, thereby reducing windage losses while maintaining cooling performance.
2Device complexity
If internal air is used for cooling, then the cooling system is simplified, but the cooling efficiency is reduced because internal air temperature is higher than external air temperature
Solution Approach 1:
The external air cooling system and internal air cooling system are merged into a unified cooling architecture where the heat exchanger serves as a bridge. The external air pathway cools the stator directly, while the internal air pathway cools the rotor, and the heat exchanger transfers thermal energy between the two pathways to improve overall cooling efficiency.
Solution Approach 2:
The heat exchanger acts as a thermal intermediary that transfers heat from the warmer internal air to the cooler external air. This intermediary device enables the internal air cooling system to maintain effectiveness despite the higher temperature of internal air, without complicating the overall system architecture.
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 achieves high motor efficiency and cooling performance by effectively transferring heat from internal air to external air through partition walls, reducing temperature increases and maintaining efficiency without enlarging fans.
Implementation Method 1
The first guide includes a first tube located between the first bracket and the stator, and multiple first partition walls. The multiple first partition walls are hollow, extend from an outer circumferential surface of the first tube, and connect the internal air bypass and an internal space of the first tube. The first guide transfers heat transferred from the internal air passing through inside the plurality of first partition walls to the external air drawn in through the inlet hole
Implementation Method 2
The first guide transfers heat transferred from the internal air passing through inside the plurality of first partition walls to the external air drawn in through the inlet hole and guides the external air to the external air passage. The second guide includes a second tube located between the second bracket and the stator, and a second partition wall. The second partition wall is hollow, extends from an outer circumferential surface of the second tube, and connects the internal air bypass and an internal space of the second tube
Data Source
AI summary
An electric motor includes a shaft, a rotor, a stator, a first bracket, a second bracket, a bypass definer, a first guide, and a second guide. The bypass definer defines an internal air bypass located radially outward from the stator for internal air to flow through. The first guide transfers heat transferred from the internal air passing through inside a plurality of first partition walls connecting the internal air bypass and an internal space to external air and guides the external air to an external air passage. The second guide transfers heat transferred from the internal air passing through inside a second partition wall connecting the internal air bypass and an internal space to the external air and guides the external air outside.