Powder Magnetic Core Multilayer Insulation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Powder magnetic cores face challenges in achieving compatibility between high magnetic flux density and high electrical resistivity due to limitations in heat resistance and insulating layer integrity, particularly when subjected to high-temperature treatments and increased compacting pressures.

Innovation Solution

A composite magnetic particle with a multilayer insulating passivation layer, where the outermost layer contains iron oxide, enhances heat resistance, adhesiveness, and uniformity, allowing for high-density compaction while maintaining magnetic properties and electrical resistivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If heat treatment temperature is increased to reduce core loss, then core loss decreases, but core resistance reduces and eddy-current loss increases

Engineering Contradiction:

Improvecore lossVSAvoidcore resistance

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The insulating passivation layer is divided into multiple layers with different functions: an inner layer containing phosphate coating for basic insulation, and an outer layer containing iron oxide for heat resistance. This segmentation allows each layer to optimize for its specific function, enabling the core to withstand high-temperature heat treatment while maintaining insulation properties.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses a composite insulating passivation layer combining phosphate coating and iron oxide coating. The phosphate layer provides good insulation properties at lower temperatures, while the iron oxide layer provides superior heat resistance. This composite structure allows the core to maintain both low core loss and high core resistance during heat treatment.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If compacting pressure is increased to increase core density, then magnetic flux density increases, but insulating layers are destroyed and electrical resistivity reduces

Engineering Contradiction:

Improvecore densityVSAvoidelectrical resistivity

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The multilayer insulating passivation layer is formed on the magnetic powder particles before compaction. This preliminary insulation treatment ensures that when high compacting pressure is applied to achieve high core density, the insulating layers are already in place to protect against particle contact and maintain electrical resistivity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The insulating passivation layer is segmented into multiple layers with the outer layer providing enhanced mechanical strength and insulation protection. This segmented structure prevents the insulating layer from being destroyed during high-pressure compaction, maintaining both core density and electrical resistivity.

Inventive Principle:

Principle #1Segmentation

3Reliability

If insulating layer thickness is increased to increase electrical resistivity, then electrical resistivity increases, but magnetic flux density decreases

Engineering Contradiction:

Improveelectrical resistivityVSAvoidmagnetic flux density

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies different qualities to different parts of the insulating structure: the inner layer provides basic insulation with moderate thickness, while the outer layer provides enhanced insulation and heat resistance. This local differentiation allows optimal balance between electrical resistivity and magnetic flux density by providing insulation exactly where needed without excessive thickness that would reduce magnetic performance.

Inventive Principle:

Principle #3Local quality

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 results in a powder magnetic core with improved electrical resistivity and magnetic flux density, effectively suppressing performance degradation at high temperatures and achieving high core resistance and magnetic permeability.

Implementation Method 1

the outermost layer contains iron oxide as a main component

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

After the compaction, a heat treatment (annealing) is performed in order to release compression strain caused during the compaction and reduce iron loss (core loss)

Methodology Applied

Scientific EffectHeat treatment (annealing): Annealing

Implementation Method 3

a soft magnetic material (powder) containing iron as the main component on which a thin insulating layer is formed by a phosphate treatment

Methodology Applied

Scientific EffectPhosphate treatment:

Implementation Method 4

a compacting pressure is increased in order to increase the density of the core

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentUS9180517B2Powder magnetic core

Publication Date: 2015.11.10 TDK CORP

AI summary

A powder magnetic core having a high electrical resistivity and a high magnetic flux density, including at least a composite magnetic particle the composite magnetic particle including: a core particle containing iron as the main component; and an insulating passivation layer formed on the core particle, wherein: the insulating passivation layer at least has an inner layer formed on the core particle and the outermost layer formed on the inner layer; and the outermost layer contains iron oxide as the main component.