Laminated Core Butted Surface Roughness for Lower Iron Loss

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Solution Overview

Problem

Laminated cores for transformers and rotary machines exhibit significant variations in iron loss due to high magnetic reluctance at the butted portions of electrical steel sheets, which is exacerbated by surface roughness and insulating coatings on the processed surfaces.

Innovation Solution

The solution involves processing electrical steel sheets to achieve an arithmetic mean roughness of 5 μm or less on 90% or more of the surface area and limiting the insulating coating to 30% or less, using methods like laser processing to generate shock waves and control surface roughness and coating presence, thereby reducing voids and improving magnetic flux flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional punching or beveling methods are used to process electrical steel sheets, then the core can be manufactured with standard processes, but the iron loss varies significantly due to high magnetic reluctance at butted portions

Engineering Contradiction:

Improveiron lossVSAvoidsurface roughness control

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The invention changes the surface roughness parameter by introducing a new processing method that achieves an arithmetic mean roughness Ra of 5 μm or less on 90% or more of the processed surface area. This parameter change directly reduces magnetic reluctance at butted portions, thereby reducing iron loss in the laminated core.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If the processed surface roughness is reduced to improve magnetic flux flow, then iron loss decreases, but the processing complexity and cost increase

Engineering Contradiction:

Improveiron lossVSAvoidprocessing method complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The invention replaces conventional mechanical processing methods (punching, beveling) with a new processing method that generates shock waves, likely using laser or ultrasonic technology. This substitution achieves superior surface roughness control (Ra ≤ 5 μm on 90%+ of surface) without the high complexity and cost associated with multiple mechanical processing steps.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If insulating coating is applied to electrical steel sheets to prevent eddy currents, then electrical insulation improves, but magnetic reluctance at butted portions increases due to coating presence

Engineering Contradiction:

Improveelectrical insulationVSAvoidiron loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The invention applies local quality control by managing insulating coating presence differently across the surface. It specifies that insulating coating should be present on 30% or less of the processed surface area, allowing smooth, coating-free regions at butted portions for optimal magnetic flux flow while maintaining sufficient electrical insulation through the remaining coated areas.

Inventive Principle:

Principle #3Local quality

4Productivity

If standard processing methods are used to manufacture laminated cores, then production efficiency is maintained, but voids form at butted portions increasing magnetic reluctance

Engineering Contradiction:

Improvecore manufacturing efficiencyVSAvoidiron loss

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The invention performs preliminary action by controlling surface roughness and insulating coating distribution during the initial processing stage, before lamination assembly. By pre-establishing smooth surfaces (Ra ≤ 5 μm) and limited coating presence (≤30% area ratio) at butted portions, the method prevents void formation during assembly, reducing magnetic reluctance and iron loss while maintaining production efficiency.

Inventive Principle:

Principle #10Preliminary action

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 approach significantly reduces iron loss in laminated cores by enhancing the smoothness of the processed surfaces and minimizing the impact of insulating coatings, leading to improved iron loss properties for both transformer and rotary machine applications.

Implementation Method 1

using methods like laser processing to generate shock waves and control surface roughness and coating presence

Methodology Applied

Scientific EffectShock wave: Shock Wave

Data Source

PatentUS20250014800A1Laminated core

Publication Date: 2025.01.09 JFE STEEL CORP

AI summary

A laminated core includes a stack of pieces of an electrical steel sheet that have a predetermined shape resulting from processing and includes a butted portion at which portions of a processed surface of the electrical steel sheet are abutted against each other. In the electrical steel sheet, an area ratio of regions of the processed surface that have an arithmetic mean roughness Ra of 5 μm or less is 90% or greater based on a total area of the processed surface.