Double-Walled Electrical Steel Sheet for Heat Pipe Cooling

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Solution Overview

Problem

Conventional electrical steel sheets with ferromagnetic materials have low thermal conductivity, limiting heat removal from windings in electrical machines and thus reducing cooling efficiency.

Innovation Solution

A double-walled electrical steel sheet with a fluid-filled interior space between two ferromagnetic plates, sealed circumferentially, enhances thermal conductivity by using principles similar to heat pipes, allowing for efficient heat transfer between a heat source and a heat sink.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ferromagnetic material is used for electrical steel sheets to achieve required magnetic properties, then magnetic performance is improved, but thermal conductivity deteriorates (low thermal conductivity limits heat removal)

Engineering Contradiction:
Improvemagnetic propertiesVSAvoidthermal conductivity
Core Design Contradiction:
ReliabilityVSTemperature

Solution Approach 1:

The patent creates a composite structure by combining two ferromagnetic plates with a fluid-filled interior space. The fluid (liquid or gas) acts as a thermal conductor between the plates, while the plates maintain magnetic properties. This composite arrangement achieves high thermal conductivity (over 1000 W/(K*m)) while preserving the magnetic functionality of the ferromagnetic materials.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The fluid in the interior space serves as an intermediary thermal conduction medium between the two ferromagnetic plates. This intermediary substance enables efficient heat transfer from the heat source side to the heat sink side without compromising the magnetic properties of the ferromagnetic plates, resolving the contradiction between magnetic performance and thermal conductivity.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of manufacture

If conventional electrical steel sheets are used, then manufacturing simplicity is maintained, but heat removal efficiency deteriorates (limiting cooling efficiency and electrical power capacity)

Engineering Contradiction:
Improvemanufacturing simplicityVSAvoidheat removal efficiency
Core Design Contradiction:
Ease of manufactureVSProductivity

Solution Approach 1:

The electrical steel sheet is segmented into two separate ferromagnetic plates with a fluid-filled space between them. This segmentation allows the fluid to circulate and efficiently carry heat away from the heat source, dramatically improving heat removal efficiency while maintaining manufacturability through standardized plate production and fluid filling processes.

Inventive Principle:
Principle #1Segmentation

3Temperature

If thermal conductivity is increased to improve cooling efficiency, then heat removal capability is improved, but device complexity increases (double-walled structure with fluid filling)

Engineering Contradiction:
Improvethermal conductivityVSAvoidstructure complexity
Core Design Contradiction:
TemperatureVSDevice complexity

Solution Approach 1:

The patent merges the structural function of the electrical steel sheet with the cooling function by integrating the fluid-filled thermal conduction path directly into the sheet structure. The two ferromagnetic plates serve both as magnetic components and as boundaries for the thermal conduction fluid, combining structural support and heat transfer functions into a single integrated component.

Inventive Principle:
Principle #5Merging (Combining)

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 significantly increases thermal conductivity from 20 to 80 W/(K*m to over 1000 W/(K*m), enabling more efficient heat exchange, increased electrical power capacity, and a more compact, lighter machine design without exceeding heat limits.

Implementation Method 1

the fluid can contain water and/or water vapor. In particular, given the conditions in the interior, in particular given the internal pressure in the interior, the fluid is gaseous at a first temperature, which corresponds, for example, to a temperature of the heat source

Methodology Applied
Scientific EffectEvaporation: Evaporation

Implementation Method 2

at a second temperature, for example a temperature of a heat sink, such as a cooling element of the electrical machine, liquid. Advantageously, if the fluid is in a first area of the interior that has an elevated temperature, for example a first area in the vicinity of the heat source, it can evaporate and thereby absorb energy from its surroundings in the form of heat. In the gas phase, that is to say in particular as vapor, the fluid can then flow

Methodology Applied
Scientific EffectCondensation: Condensation

Implementation Method 3

The structure of the electrical steel sheet according to the improved concept, in particular the interior space with the fluid, can decisively improve the thermal conductivity of the electrical steel sheet as an overall system. For this purpose, the improved concept makes use of physical principles, such as those that can also underlie embodiments of heat pipes.

Methodology Applied
Scientific EffectHeat pipe: Heat Pipe

Data Source

PatentEP3909113B1Electrical sheet for an electrical machine and method for producing an electrical sheet
Publication Date: 2023.04.26 SIEMENS AG
  • EP3909113B1 patent drawingFigure 1~2
  • EP3909113B1 patent drawingFigure 3~4

AI summary

To achieve heat transport between a heat source and a heat sink of an electrical machine, an electrical sheet for an electrical machine is disclosed, wherein the electrical sheet has two plates (1, 2) made of ferromagnetic material, which are arranged parallel to each other and at a distance (5) from one another. The plates (1, 2) are connected circumferentially in a fluid-tight manner to one another on respective edges of the plates. A fluid (5) is located between the plates in an interior formed by the distance (5).