Internal Stator Composite Structure for Ring Coil Interference

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Solution Overview

Problem

Existing electric machine configurations with ring type coils interfere geometrically and electromagnetically with conventional stator structures, limiting their efficiency and compatibility in high-frequency applications.

Innovation Solution

The electric machine incorporates an internal stator made of three dissimilar materials: a high magnetic property material for the back iron, a non-magnetic material with high electric resistivity for the connectors, and a rigid, machinable material for the central hub, with ring coils wound around the bearing and between teeth, and connectors welded to the back iron and hub to minimize interference and facilitate assembly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If ring type coils are used in the stator, then high-frequency performance and torque density are improved, but geometric and electromagnetic interference with conventional stator structures occurs

Engineering Contradiction:
Improvetorque densityVSAvoidelectromagnetic interference
Core Design Contradiction:
PowerVSObject-affected harmful factors

Solution Approach 1:

The stator is constructed using composite materials: the back iron is made of high magnetic permeability material (such as electrical steel) to guide magnetic flux, while the connectors are made of non-magnetic material with high electric resistivity (such as aluminum or copper) to minimize electromagnetic interference and eddy current losses. This composite structure allows ring type coils to achieve high torque density without suffering from electromagnetic interference with conventional stator structures.

Inventive Principle:
Principle #40Composite materials

2Reliability

If ring type coils are wound around the back iron, then leakage inductance is reduced, but geometric interference with conventional stator structure occurs

Engineering Contradiction:
Improveleakage inductanceVSAvoidstator structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The stator is segmented into distinct functional components: the back iron (for magnetic flux conduction) and the connectors (for structural support and electrical isolation). This segmentation allows ring type coils to be wound around the back iron to reduce leakage inductance, while the connectors are strategically designed to avoid geometric interference with the coil windings.

Inventive Principle:
Principle #1Segmentation

3Strength

If connectors are added to connect back iron to hub, then structural integrity is improved, but manufacturing complexity increases

Engineering Contradiction:
Improvestructural integrityVSAvoidmanufacturing complexity
Core Design Contradiction:
StrengthVSEase of manufacture

Solution Approach 1:

The connectors are designed with pre-formed attachment features that facilitate assembly. The connectors are manufactured separately with predetermined geometry and connection interfaces, allowing the back iron, connectors, and hub to be assembled in a standardized sequence. This preliminary design of connection interfaces reduces manufacturing complexity while maintaining structural integrity.

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

The solution reduces electromagnetic interference, enables mass production, and supports high torque and high-frequency operations, achieving over 10000 Newton Meters of torque with minimal distortion and stress.

Implementation Method 1

the first material may have high magnetic properties

Methodology Applied
Scientific EffectMagnetic properties: Ferromagnetism

Implementation Method 2

the second material may have non-magnetic properties with high electric resistivity

Methodology Applied
Scientific EffectElectric resistivity: Electrical Resistance

Implementation Method 3

connectors welded to the back iron and hub

Methodology Applied
Scientific EffectWelding: Welding

Data Source

PatentEP3867997B1Electric machine structure and technology
Publication Date: 2025.12.03 CUMMINS INC
  • EP3867997B1 patent drawingFigure 1
  • EP3867997B1 patent drawingFigure 2
  • EP3867997B1 patent drawingFigure 3

AI summary

The electric machine includes a rotor and an internal stator operatively coupled to the rotor. The internal stator further includes a back iron having a bearing and a plurality of teeth, a plurality of ring coils wound around the back iron, a central hub, and a plurality of connectors that connects the central hub to the back iron. The back iron is made of a first material and at least one connector is made of a second material that is different from the first material.