Segmented Stator Pole Layout for Lower-Loss Transverse Flux Machines

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Solution Overview

Problem

Transverse flux machines face limitations in torque density and thermal management due to eddy current losses and leakage flux issues, particularly in claw pole geometries, which restrict their operating range to low speeds and frequencies.

Innovation Solution

The design incorporates a stator pole with a ferromagnetic body element featuring a curved magnetic return path region that occupies only a portion of the circumference, reducing leakage flux and eddy current losses, and allows for improved cooling by creating a grid structure for fluid flow between stator poles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If claw-shaped geometry with laminated iron sheets is used for flux guidance, then magnetic permeability and saturation flux density are improved, but eddy current losses increase when flux is directed perpendicular to lamination

Engineering Contradiction:

Improvemagnetic flux guidance effectivenessVSAvoideddy current losses

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The stator pole is divided into multiple segments in the circumferential direction, with each segment having its own body element and magnetic return path region. This segmentation allows the magnetic flux to be guided through multiple separate paths, reducing eddy current losses while maintaining effective flux guidance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a third dimension by creating a curved magnetic return path region that extends in the radial direction and occupies only a portion of the circumference. This three-dimensional configuration allows flux to be guided effectively while reducing eddy currents compared to traditional planar laminated structures.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Device complexity

If air cooling is used instead of liquid cooling, then system complexity is reduced, but thermal capacity and cooling efficiency decrease

Engineering Contradiction:

Improvecooling system complexityVSAvoidthermal management capability

Core Design Contradiction:

Device complexityVSTemperature

Solution Approach 1:

The stator pole segmentation creates multiple cooling channels between the pole segments, allowing cooling fluid to flow through these channels and efficiently remove heat from the windings and magnetic circuits, thereby improving thermal capacity while maintaining relatively simple system architecture.

Inventive Principle:

Principle #1Segmentation

3Power

If high number of pole pairs with fine pole pitch is achieved, then torque density at low speed is improved, but leakage flux and eddy current losses increase

Engineering Contradiction:

Improvetorque densityVSAvoidleakage flux losses

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

By dividing the stator pole into multiple segments with individual magnetic return path regions, the patent reduces leakage flux between adjacent poles while maintaining fine pole pitch configurations, thereby reducing eddy current losses without sacrificing torque density.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each stator pole segment is equipped with its own optimized magnetic return path region, allowing local optimization of flux guidance to minimize leakage flux in high pole pair configurations while maintaining overall torque density.

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

This configuration enhances torque density, reduces thermal losses, and increases the operating range of transverse flux machines by improving magnetic flux guidance and cooling efficiency.

Implementation Method 1

The stator pole has a body element made of a ferromagnetic material, which has at least one first pole head and a magnetic return path region

Methodology Applied

Scientific EffectFerromagnetism: Ferromagnetism

Implementation Method 2

A transverse flux machine is a rotating electrical machine in which a relevant magnetic flux arises substantially transversely or perpendicularly to an axis of rotation

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 3

In order to reduce eddy currents in the normal operation of the transverse flux machines, this material is frequently provided in laminated form

Methodology Applied

Scientific EffectEddy currents: Eddy Currents

Data Source

PatentUS11799331B2Transverse flux machine

Publication Date: 2023.10.24 ROLLS ROYCE DEUT LTD & CO KG

AI summary

A stator pole for a stator of a transverse flux machine is provided. The stator includes a stator winding arranged in a winding space, and the winding space being formed circumferentially in a circumferential direction in relation to an axis of rotation of a rotor. The stator pole has a body element made of a ferromagnetic material, which has at least one pole head which, in the installation position, may be arranged opposite the one rotor, and a magnetic return path region, which may be arranged facing away from the one rotor, wherein a number of the pole heads of the stator pole correspond to a number of the rotors. The stator pole is configured to occupy only a portion of a circumference of the winding space in the circumferential direction, and the magnetic return path region has a curved shape which adjoins the at least one pole head, as a result of which the magnetic return path region is designed to define the winding space in part transversely to the circumferential direction.