Current Transformer Unit With Dielectric Air Space

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Solution Overview

Problem

High voltage transformers face challenges with partial discharge due to air voids between dielectric layers, leading to electrical breakdown and signal fidelity issues, which are difficult and costly to address through conventional methods like vacuum filling or increasing dielectric thickness, especially in compact applications.

Innovation Solution

A transformer unit with a dielectric housing and magnetic core configuration that creates a dielectric air space between the magnetic core and coils, using positioning portions to maintain a minimum air distance and reduce electrical field strength, thereby eliminating or reducing partial discharge.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a dielectric layer is positioned against and surrounds the magnetic core with coils wound directly over it, then the insulation protection is provided, but small air spaces or voids are created between coil windings and dielectric layer which favor partial discharge

Engineering Contradiction:
Improveinsulation protectionVSAvoidpartial discharge
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention extracts the harmful air voids from the dielectric layer by creating a dedicated dielectric air space between the magnetic core and coil windings. This is achieved by positioning the coils at a distance from the core using support structures, thereby eliminating the voids that would otherwise form between tightly wound coils and the dielectric layer, and removing the source of partial discharge

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The invention introduces an intermediary dielectric air space between the magnetic core and coil windings. This air space acts as a mediator that provides dielectric separation and prevents direct contact between coils and the core, thereby eliminating partial discharge while maintaining insulation protection

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If the dielectric layer thickness is increased to eliminate partial discharge, then partial discharge is reduced, but the device volume, mass and cost increase

Engineering Contradiction:
Improvepartial discharge eliminationVSAvoidtransformer volume
Core Design Contradiction:
ReliabilityVSVolume of stationary object

Solution Approach 1:

The invention segments the dielectric structure into two distinct parts: a thin dielectric layer surrounding the magnetic core for protection, and a separate dielectric air space between the core and coils. This segmentation allows the thin layer to provide insulation while the air space eliminates partial discharge, avoiding the need for a single thick dielectric layer that would increase volume

Inventive Principle:
Principle #1Segmentation

3Reliability

If conventional methods like vacuum filling or increasing dielectric thickness are used to address partial discharge, then partial discharge is reduced, but the manufacturing complexity and cost increase

Engineering Contradiction:
Improvepartial discharge reductionVSAvoidmanufacturing simplicity
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The invention performs preliminary action by pre-positioning the coil windings at a specific distance from the magnetic core using support structures during manufacturing. This preliminary positioning creates the dielectric air space before the transformer is put into service, eliminating the need for post-manufacturing processes like vacuum filling or complex dielectric application

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 provides a compact, economical, and reliable transformer unit that effectively reduces partial discharge, ensuring stable signal transmission and power transfer across high voltage differences, while being easy to produce and assemble, even in limited spaces.

Implementation Method 1

there may be a phenomenon of partial discharge that could eventually lead to an electrical breakdown or have an adverse effect on the performance of the transformer

Methodology Applied
Scientific EffectPartial discharge: Townsend Discharge

Implementation Method 2

provides a dielectric separation that should withstand breakdown of the dielectric due to the voltage difference

Methodology Applied
Scientific EffectDielectric separation: Dielectric

Data Source

PatentEP2667389B1Current Transformer Unit
Publication Date: 2014.12.17 LEM INTPROP
  • EP2667389B1 patent drawingFigure 1~2
  • EP2667389B1 patent drawingFigure 3~4
  • EP2667389B1 patent drawingFigure 5~6

AI summary

A transformer (3, 3') including a housing (6), a magnetic core (10, 10') and transformer coils (12, 12') wound around the housing. The housing (6) defines a magnetic core receiving cavity (20, 20') in which the magnetic core (10, 10') is mounted. The housing further comprises positioning portions (8) projecting from walls of the housing in the magnetic core receiving cavity, configured to position the magnetic core in the magnetic core receiving cavity to form a dielectric air space (15, 15') between the magnetic core and the transformer coil.