Litz Wire Ferrule Termination Without Braid Disruption

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Solution Overview

Problem

Conventional Litz wire terminal assemblies require insulation removal and straightening of wire bundles, which disrupts the braid pattern, leading to heat issues and reduced efficiency due to skin effect, and often use damaging chemical baths.

Innovation Solution

A Litz wire terminal assembly that maintains the braid pattern by using a ferrule and ultrasonic welding to form a metallurgical bond between the wire bundle and a metal surface, eliminating the need for insulation stripping and chemical baths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the Litz wire bundle is straightened to expand conductive material volume, then the termination connection is improved, but the braid pattern is altered which increases skin effect and heat generation

Engineering Contradiction:
Improvetermination connection reliabilityVSAvoidconductor temperature due to skin effect
Core Design Contradiction:
ReliabilityVSTemperature

Solution Approach 1:

The invention introduces a ferrule that segments the wire bundle into two functional zones: the insulated portion maintains the braid pattern for low skin effect, while the exposed portion within the ferrule provides reliable electrical connection. This segmentation allows simultaneous achievement of both connection reliability and thermal performance.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The ferrule acts as an intermediary component between the Litz wire bundle and the electrical connection point. It provides a interface that accommodates the wire bundle without requiring straightening, thereby maintaining the braid pattern while enabling reliable termination through its internal structure and bonding mechanism.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Stability of the object's composition

If chemical baths are used to remove insulation, then the braid pattern can be maintained, but the wire strands are damaged reducing overall performance

Engineering Contradiction:
Improvebraid pattern stabilityVSAvoidwire strand integrity
Core Design Contradiction:
Stability of the object's compositionVSReliability

Solution Approach 1:

The invention extracts only the necessary portion of insulation from individual wire strands at the termination end, rather than removing insulation from the entire bundle. This selective extraction allows the ferrule to make contact with conductive material while the majority of the braid pattern remains insulated and intact, preserving both electrical connection and structural integrity.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The insulation removal is applied locally only where needed for electrical connection within the ferrule, while the rest of the wire bundle maintains its original insulated structure. This localized treatment preserves the braid pattern's electromagnetic properties while enabling reliable termination.

Inventive Principle:
Principle #3Local quality

3Reliability

If insulation is removed from wire strands, then electrical connection is improved, but the process becomes more complex and time-consuming

Engineering Contradiction:
Improveelectrical connection qualityVSAvoidtermination process complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The invention merges the insulation removal function with the ferrule structure itself. The ferrule is designed to accommodate the insulated bundle and selectively expose conductive material through its geometry and bonding process, combining what were previously separate steps into an integrated solution that reduces overall process 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

This solution maintains the braid pattern, reducing heat-related issues and improving performance by preventing damage to the wires, while also reducing costs and time compared to conventional methods.

Implementation Method 1

Each conductive strand is ultrasonically welded to the metal surface such that the distal bundle end is thermally adhered to the metallic surface

Methodology Applied
Scientific EffectUltrasonic welding: Ultrasonic Vibration

Implementation Method 2

The wire bundle is thermally adhered to the lug, thereby forming a metallurgical bond between the two components

Methodology Applied
Scientific EffectThermal adhesion: Heating

Data Source

PatentEP3029773B1Litz wire terminal assembly
Publication Date: 2024.02.28 HAMILTON SUNDSTRAND CORP
  • EP3029773B1 patent drawingFigure 1
  • EP3029773B1 patent drawingFigure 2
  • EP3029773B1 patent drawingFigure 3

AI summary

A Litz wire terminal assembly includes a wire bundle 102 having a plurality of electrically conductive strands 104 extending between a first end 106 a and a second end 106 b to define a length. Each strand includes an insulative cover having a proximate cover end at the first end and a distal cover end at the second end. The distal cover end is flush with the second end. The Litz wire terminal assembly further includes a ferrule 108 on the wire bundle. The ferrule has a distal ferrule end at the second end of the conductive strands.