Stator Pole Composite Structure for Lower Eddy Current Loss

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Solution Overview

Problem

Eddy currents generated in ferromagnetic components of electrical machines due to time-varying magnetic fields lead to inefficiencies and ohmic heating, reducing the efficiency of permanent magnet electrical machines.

Innovation Solution

Incorporation of ferromagnetic composite pole portions, such as soft magnetic composite, at the radially-inward and -outward extents of stator magnetic poles, with rounded corners, to minimize eddy current generation by reducing the surface area exposed to fringing magnetic fields.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ferromagnetic laminations are used in stator magnetic poles, then magnetic field conduction is improved, but eddy current losses and ohmic heating increase due to exposure to fringing magnetic fields

Engineering Contradiction:

Improvemagnetic field conductionVSAvoideddy current losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The stator magnetic pole is segmented into multiple ferromagnetic lamination layers stacked together, with each lamination electrically insulated from others. This segmentation breaks the continuous conductive path that would otherwise allow large eddy currents to flow through the entire pole structure, thereby reducing eddy current losses while maintaining magnetic field conduction capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses composite construction by stacking multiple ferromagnetic laminations with electrical insulation between them, creating a layered composite structure. This composite approach allows the pole to simultaneously achieve good magnetic conductivity (through the ferromagnetic material) and reduced eddy current losses (through the insulating layers that interrupt current paths)

Inventive Principle:

Principle #40Composite materials

2Force

If ferromagnetic pole portions are extended to radially-inward and -outward extents, then magnetic pole strength is improved, but eddy current generation increases due to larger surface area exposed to fringing fields

Engineering Contradiction:

Improvemagnetic pole strengthVSAvoideddy current generation

Core Design Contradiction:

ForceVSLoss of energy

Solution Approach 1:

The extended pole portions are constructed from stacked ferromagnetic laminations rather than solid ferromagnetic material. This segmentation maintains the magnetic pole strength by providing sufficient magnetic conductivity across the extended radial extents, while the laminated structure with insulating layers reduces eddy current generation by interrupting current paths in the extended regions exposed to fringing fields

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different structural configurations to different radial zones of the magnetic pole. The pole portions at radially-inward and -outward extents, which are most exposed to fringing fields, are specifically constructed with laminated ferromagnetic material to reduce eddy currents, while maintaining adequate magnetic pole strength through proper lamination stacking and arrangement

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

Reduces eddy current losses and ohmic heating, enhancing the efficiency of electrical machines by minimizing the impact of fringing magnetic fields on stator laminations.

Implementation Method 1

One inefficiency in electrical machines and other apparatuses that employ time-varying magnetic fields is the generation of eddy currents in the ferromagnetic components of the machine

Methodology Applied

Scientific EffectEddy currents: Eddy Currents

Implementation Method 2

the ferromagnetic composite pole portion or portions may be located in an area or areas of fringing of magnetic fields generated by the permanent magnets of the rotor

Methodology Applied

Scientific EffectFringing magnetic fields: Magnetic Field

Implementation Method 3

the rotor including a plurality of permanent magnets facing the stator magnetic poles

Methodology Applied

Scientific EffectMagnetic fields: Magnetic Field

Implementation Method 4

Permanent magnet electrical machines have the potential to provide high power density and high efficiency

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 5

Each stator magnetic pole includes a plurality of ferromagnetic laminations in a lamination stack

Methodology Applied

Scientific EffectFerromagnetism: Ferromagnetism

Implementation Method 6

a plurality of ferromagnetic laminations in a lamination stack that extends from a radially-inward extent to a radially-outward extent

Methodology Applied

Scientific EffectLamination: Lamination

Data Source

PatentUS12567772B2Electrical machine

Publication Date: 2026.03.03 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

An electrical machine includes a rotationally-fixed stator defining a rotational axis of the electrical machine and having a plurality of stator magnetic poles, the stator magnetic poles disposed about the rotational axis. The electrical machine also has a rotor rotatably mounted coaxially with the rotational axis and axially spaced from the stator, the rotor having a plurality of permanent magnets facing the stator magnetic poles. Each stator magnetic pole includes a plurality of ferromagnetic laminations in a lamination stack that extends from a radially-inward extent to a radially-outward extent relative to the rotational axis, and a ferromagnetic composite pole portion affixed to the radially-outward extent or the radially-inward extent of the lamination stack of the stator magnetic pole.