Composite Rotor Wedge Structure for Lower Eddy Current Loss

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Solution Overview

Problem

Existing wedges in electrical generators suffer from increased eddy current losses due to their electrical conductivity, which cannot be mitigated without also increasing friction and windage losses.

Innovation Solution

A rotor wedge design featuring a central portion made of electrically non-conductive material, such as titanium, with electrically conductive wings, like aluminum, to minimize eddy current losses while maintaining low friction and windage losses, and incorporating coolant oil flow apertures and steel fasteners for structural integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If electrically non-conductive material is used for the wedge to reduce eddy current losses, then eddy current losses are minimized, but thermal conductivity is reduced

Engineering Contradiction:

Improveeddy current lossesVSAvoidheat transfer efficiency

Core Design Contradiction:

Loss of energyVSTemperature

Solution Approach 1:

The wedge is designed with different material properties in different regions: the outer surface contacting laminations is made electrically non-conductive (e.g., titanium) to prevent eddy currents, while the inner portion is made electrically conductive (e.g., aluminum) to maintain thermal conductivity for heat transfer from the field coils. This local differentiation resolves the contradiction by assigning different functional qualities to different parts of the same component.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The wedge combines two different materials with complementary properties: an electrically non-conductive material for the outer surface to minimize eddy current losses, and an electrically conductive material for the inner portion to maintain thermal management. This composite approach allows simultaneous optimization of both energy loss types that were previously mutually exclusive.

Inventive Principle:

Principle #40Composite materials

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 design effectively reduces eddy current losses while preserving low friction and windage losses, enhancing thermal conductivity and allowing efficient heat transfer.

Implementation Method 1

Wedges on electromagnetic machines are typically electrically conductive and thus have associated losses due to eddy currents

Methodology Applied

Scientific EffectEddy current: Eddy Currents

Implementation Method 2

The second material can include aluminum. The central portion is primarily composed of the second material

Methodology Applied

Scientific EffectThermal conductivity: Conduction (thermal)

Implementation Method 3

The central portion can include an aperture configured to allow coolant oil flow

Methodology Applied

Scientific EffectConvection cooling: Convection

Data Source

PatentEP4024673B1Wedge for rotor field coils and rotor comprising the same

Publication Date: 2026.02.25 HAMILTON SUNDSTRAND CORP

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AI summary

A wedge (32) for use in an electric machine includes a central portion (40) comprising at least a first material, a first wing (46) integrally attached to the central portion (40), and a second wing (48) integrally attached to the central portion (40) opposite the first wing (46), wherein the first wing (46), and the second wing (48) include a second material.