Annular Excitation Core for Clamp Current Sensor

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Solution Overview

Problem

Conventional excitation cores made of thin strip-shaped magnetic substances struggle with mechanical strength and reproducibility in divided clamp-type contactless current sensors, leading to contact failures and unreliable current measurement due to the linear shape of the magnetic substance layers, which results in small contact areas and poor magnetic coupling during opening and closing operations.

Innovation Solution

An excitation core design featuring an annular strip-shaped magnetic substance with overlapping ends and a reinforcing body made of non-magnetic material, allowing for sufficient contact area maintenance and enhanced mechanical strength, where the magnetic substance is positioned on the reinforcing body and can pass through a through-hole, ensuring stable contact and operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If thin strip-shaped magnetic substances are wound and stacked into several layers to create the excitation core, then cost is reduced and performance is improved, but mechanical strength deteriorates and contact reliability becomes poor due to linear shape resulting in small contact areas

Engineering Contradiction:

Improvecontact reliabilityVSAvoidmechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies curvature by forming the magnetic substance into an annular shape instead of a linear strip. The both ends of the annular magnetic substance are overlapped in the thickness direction to form a contact portion, creating a curved/rounded structure that increases contact area and improves mechanical strength while maintaining the thin strip-shaped material benefits

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Ease of manufacture

If thin strip-shaped magnetic substances are used to improve performance and reduce cost, then manufacturing cost is reduced, but contact area becomes small leading to poor magnetic coupling and unreliable operation

Engineering Contradiction:

Improvemanufacturing costVSAvoidmagnetic coupling reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The annular configuration with overlapped ends creates a rounded contact geometry that significantly increases the contact area between magnetic substance layers, improving magnetic coupling reliability while still using cost-effective thin strip-shaped materials

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The both ends of the annular magnetic substance are overlapped in the thickness direction, creating a nested configuration where one end is positioned within the thickness of the other end, forming a reliable contact portion that maintains magnetic coupling

Inventive Principle:

Principle #7Nested doll (Nesting)

3Adaptability or versatility

If the excitation core is designed for divided clamp-type contactless current sensors, then adaptability is improved, but contact failures occur during opening and closing operations due to insufficient contact area

Engineering Contradiction:

Improvesensor adaptabilityVSAvoidcontact stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The annular shape with overlapped ends provides a rounded contact structure that maintains stable magnetic coupling during opening and closing operations of divided clamp-type sensors, preventing contact failures while maintaining sensor adaptability

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The both ends are pre-positioned to overlap in the thickness direction during manufacturing, creating a contact portion before the sensor is assembled or operated, ensuring reliable contact is established before any opening or closing operations occur

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 enables the use of thin strip-shaped magnetic substances in divided clamp-type contactless current sensors, maintaining mechanical strength and sensor properties while ensuring reliable current measurement by maintaining sufficient contact areas and preventing contact failures during opening and closing operations.

Implementation Method 1

the linear shape of the magnetic substance layers, which results in small contact areas and poor magnetic coupling during opening and closing operations

Methodology Applied

Scientific EffectMagnetic coupling: Magnetism

Data Source

PatentUS10782321B2Excitation core, sensor head, and current sensor

Publication Date: 2020.09.22 YOKOGAWA ELECTRIC CORP

AI summary

An excitation core includes an annular strip-shaped magnetic substance, in which both ends of the strip-shaped magnetic substance are overlapped in a thickness direction and are in contact with one another. A sensor head includes: this excitation core and a magnetism collecting body. The magnetism collecting body includes a strip-shaped first magnetism collector and a strip-shaped second magnetism collector, the first magnetism collector having both ends thereof in contact with both ends of the second magnetism collector to form the annular magnetism collecting body, the magnetism collecting body being disposed on an inside or an outside of the reinforcing body.