Rotary Transformer Core Structure for Low-Loss Motor Power Transfer

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Solution Overview

Problem

Existing motor systems face inefficiencies in power transmission and energy loss due to leakage fluxes and eddy currents, particularly in rotary transformers with contact-based power transmission methods.

Innovation Solution

A contactless electric power transmission device utilizing a magnetic core with cavities and openings, a rotary member with windings, and magnetic bodies to suppress leakage fluxes and reduce energy loss, enhancing motor efficiency through a rotary transformer design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If contact-based power transmission is used in rotary transformers, then power transmission is achieved, but energy loss increases due to leakage fluxes and eddy currents

Engineering Contradiction:
Improveenergy lossVSAvoidpower transmission reliability
Core Design Contradiction:
Loss of energyVSReliability

Solution Approach 1:

A magnetic core with a specific structure (including a yoke and armatures with windings) is introduced as an intermediary to enable contactless power transmission. The magnetic core guides and contains the magnetic flux, preventing leakage fluxes from causing energy loss while maintaining reliable power transmission from stator to rotor.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces contact-based mechanical power transmission with contactless electromagnetic induction. By using a magnetic core and windings that generate magnetic fields, the system eliminates physical contact between stator and rotor, thereby preventing eddy currents and leakage fluxes that cause energy loss.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Loss of energy

If motor efficiency is improved through contactless power transmission, then energy loss is reduced, but device complexity increases due to additional magnetic components

Engineering Contradiction:
Improveenergy lossVSAvoiddevice complexity
Core Design Contradiction:
Loss of energyVSDevice complexity

Solution Approach 1:

The magnetic core serves multiple functions simultaneously: it provides a path for magnetic flux, supports the windings, and prevents leakage fluxes. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while achieving reduced energy loss.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines the magnetic flux path and the winding support structure into a single integrated magnetic core assembly. The yoke and armatures are merged to form a complete magnetic circuit that also serves as the structural framework for mounting the windings, thereby reducing component count and assembly complexity.

Inventive Principle:
Principle #5Merging (Combining)

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 effectively reduces energy loss and increases motor efficiency over a wide range of rotation speeds by minimizing leakage fluxes and eddy currents, improving reliability and reducing inertial forces.

Implementation Method 1

a magnetic core having a ring shape including a through hole through which a shaft extends... a first winding provided in the cavity and wound along the circumferential direction... a second winding provided on the rotary member and wound along the circumferential direction

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

a first magnetic body provided along the circumferential direction in a part of the rotary member corresponding to the first opening of the magnetic core

Methodology Applied
Scientific EffectMagnetic flux containment: Magnetic Field

Data Source

PatentEP4668300A1Power transmission device and motor device
Publication Date: 2025.12.24 TDK CORP
  • EP4668300A1 patent drawingFigure 1
  • EP4668300A1 patent drawingFigure 2
  • EP4668300A1 patent drawingFigure 3

AI summary

An electric power transmission device according to one embodiment of the invention includes a magnetic core, a first winding, a rotary member, a second winding, and a first magnetic body. The magnetic core has a ring shape including a through hole through which a shaft extends. The magnetic core includes therein a cavity along a circumferential direction about an axis of rotation of the shaft, and has a first opening provided along the circumferential direction in a first surface in contact with the through hole, and coupling the through hole and the cavity to each other. The first winding is provided in the cavity and wound along the circumferential direction. The rotary member is provided at a position corresponding to the first opening in an axial direction of the axis of rotation, and is rotationally movable, inside the cavity, in the circumferential direction with a rotation of the shaft. The second winding is provided on the rotary member and wound along the circumferential direction. The first magnetic body is provided along the circumferential direction in a part of the rotary member corresponding to the first opening of the magnetic core.