Ferritic Lamination Stack with Insulating Asperities for Corrosion Resistance

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Solution Overview

Problem

Existing rotating electrical machines with magnetic bearings face challenges in maintaining magnetic properties and corrosion resistance when operating in corrosive environments, as current solutions either compromise magnetic performance or increase manufacturing complexity and cost.

Innovation Solution

A lamination stack formed from ferritic stainless steel sheets with chemically protective, electrically insulating coatings, where the sheets are prepared with surface asperities and stacked with insulating material, then compressed and heat-treated to create a robust, corrosion-resistant, and magnetically efficient structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If silicon-iron lamination stacks are used in corrosive environments, then excellent magnetic properties are achieved, but corrosion resistance deteriorates

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidmagnetic property degradation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies composite materials by combining ferritic stainless steel sheets with organic insulating layers to create a lamination stack that integrates both corrosion resistance and magnetic properties. The ferritic stainless steel provides corrosion resistance while the organic layer provides electrical insulation, eliminating the need for additional protective measures.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the stator is encapsulated by a corrosion resistant jacket, then corrosion resistance is improved, but the airgap must be enlarged which decreases magnetic properties

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidairgap dimension

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent uses thin organic insulating layers (films) coated directly on the lamination sheets instead of thick encapsulating jackets. This approach provides corrosion protection while maintaining the original airgap dimensions, thereby preserving magnetic properties such as field sensitivity.

Inventive Principle:

Principle #30Flexible shells and thin films

3Reliability

If ferritic stainless steel is used for rotor laminations, then corrosion resistance is improved, but magnetic properties are compromised

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidmagnetic property quality

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent creates a composite structure where ferritic stainless steel sheets are combined with organic insulating layers. This composite approach maintains the corrosion resistance of ferritic stainless steel while the organic layer compensates for any magnetic property compromises by providing electrical insulation that reduces eddy current losses.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the physical and chemical parameters of the ferritic stainless steel sheets by coating them with organic insulating material. This modification alters the surface properties to enhance corrosion resistance while maintaining the bulk magnetic properties of the ferritic stainless steel.

Inventive Principle:

Principle #35Parameter changes

4Ease of manufacture

If adhesive is applied by silkscreen and stack is compressed, then lamination is achieved, but the structure cannot be used in corrosive environments

Engineering Contradiction:

Improvelamination processVSAvoidcorrosion resistance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent replaces the mechanical adhesive bonding system with a thermal bonding system. Instead of using adhesive applied by silkscreen, the organic insulating material is melted and bonded to the ferritic stainless steel sheets through heating, eliminating the need for additional adhesive materials that would compromise corrosion resistance.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables rotating electrical machines to operate efficiently in corrosive environments with enhanced corrosion resistance and magnetic properties, maintaining high relative permeability and saturation magnetization without compromising mechanical or electrical properties.

Implementation Method 1

heating the compressed stack at a temperature above a melting temperature of the insulating material

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

The first and second sides have asperities with a height of about two microns

Methodology Applied

Scientific EffectMechanical interlocking:

Data Source

PatentUS11728696B2Lamination stack for use in an electrical machine

Publication Date: 2023.08.15 SKF MAGNETIC MECHATRONICS SAS

AI summary

A lamination stack for use in a rotating electrical machine includes a plurality of sheets of ferritic material. Each of the sheets has first and second sides that include asperities, and the asperities have a height of about two microns and a width of about two microns. A layer of electrically insulating material is provided between adjacent pairs of the ferritic sheets in the stack, and the asperities extend into the electrically insulating material.