Electric Machine Rotor Cooling via Segmented Radial Channels

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Solution Overview

Problem

Asynchronous electric machines face limited cooling efficiency, particularly in the inner areas of the rotor, which restricts their performance due to reliance on ambient air cooling, leading to significant heat buildup.

Innovation Solution

The implementation of separate cooling channels for different fluids, with liquid and gas cooling fluids being supplied through a rotor shaft and axial openings or grooves in the laminated core, allowing for radial penetration and efficient heat dissipation via centrifugal force-assisted fluid transport.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If ambient air cooling is used for the rotor, then the structure remains simple, but the cooling efficiency of the inner rotor area is insufficient

Engineering Contradiction:
Improvecooling efficiencyVSAvoidcooling system complexity
Core Design Contradiction:
TemperatureVSDevice complexity

Solution Approach 1:

The cooling system is segmented into multiple independent cooling channels (first cooling channel and second cooling channel) that can be supplied with different cooling fluids. This segmentation allows targeted cooling of different rotor regions, improving overall cooling efficiency while maintaining manageable system complexity through modular channel design.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Different cooling fluids are supplied to different cooling channels based on local cooling requirements. The first cooling fluid is routed to the laminated core while the second cooling fluid is routed through the short-circuit ring, providing locally optimized cooling quality for each component's specific thermal characteristics.

Inventive Principle:
Principle #3Local quality

2Power

If high power density is achieved, then the performance of the electric machine increases, but heat generation increases requiring more advanced cooling

Engineering Contradiction:
Improvepower densityVSAvoidheat dissipation requirement
Core Design Contradiction:
PowerVSTemperature

Solution Approach 1:

The cooling system is divided into separate channels that can handle different cooling loads independently. This segmentation enables the system to manage high heat generation from high power density operations by directing appropriate cooling fluids to specific high-heat regions, effectively dissipating waste heat without compromising performance.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent utilizes fluid-based cooling systems (liquid and gas cooling fluids) routed through dedicated channels to efficiently remove heat generated during high power operation. The hydraulic and pneumatic principles enable controlled fluid flow through the rotor structure, providing effective heat transfer from high-power density regions.

Inventive Principle:
Principle #29Pneumatics and hydraulics

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 enhanced cooling system improves rotor cooling efficiency, increasing the performance of electric machines by directly dissipating waste heat from the generation area and utilizing centrifugal forces for fluid transport.

Implementation Method 1

Waste heat generated in the rotor can thus be dissipated directly from the area in which it is generated

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

when the cooling fluid is conveyed toward the outer edge of the rotor, the centrifugal force occurring during rotation of the rotor can be used for fluid transport

Methodology Applied
Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentEP3324517B1Electric machine
Publication Date: 2020.04.15 AUDI AG
  • EP3324517B1 patent drawingFigure 1
  • EP3324517B1 patent drawingFigure 2~3
  • EP3324517B1 patent drawingFigure 4~5

AI summary

An electric machine comprising a stator (2) and a rotor (3, 20), wherein the rotor (3, 20) comprises a laminated core (5, 23) attached to a rotor shaft (4, 25) of the electric machine (1, 49) made of laminates (26, 27, 28, 29, 37, 38) stacked in the axial direction of the rotor (3, 20), wherein the laminated core (5, 23) and/or at least a short-circuit ring (6) arranged on an axial side of the laminated core (5, 23) form at least one cooling channel (7, 8, 9, 10, 21, 22) for a cooling fluid, which extends at least section by section in the radial direction of the rotor (3, 20).