Vacuum Interrupter Contact Geometry for Stable Low Resistance

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Solution Overview

Problem

Vacuum interrupters used in vacuum circuit breakers and vacuum contactors face challenges in achieving both reduction and stability in contact resistance, particularly when contacts frequently open and close, leading to issues like slippage, increased contact resistance, and potential overheating.

Innovation Solution

The vacuum interrupter design incorporates a spherical contact surface on the fixed side contact and a planar contact surface on the movable side contact, which increases the contact area and reduces contact resistance, while also balancing the horizontal components of the contact load and reaction force to minimize slippage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If spherical contacts are used on both fixed and movable sides, then contact area is increased and contact resistance is reduced, but slippage occurs on the contact surfaces leading to coagulation formation and increased contact resistance

Engineering Contradiction:

Improvecontact resistanceVSAvoidcontact stability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies asymmetry by making the fixed side contact surface spherical while the movable side contact surface is planar. This asymmetric configuration prevents slippage that occurs with symmetric spherical-spherical contacts, while still maintaining a large contact area for low contact resistance. The spherical fixed contact provides a large initial contact area, and the planar movable contact prevents relative sliding motion.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent uses spheroidality by providing a spherical contact surface on the fixed side contact. This curved surface increases the contact area compared to flat contacts, reducing contact resistance. The spherical shape works in combination with the planar movable contact to achieve both low contact resistance and stable contact without slippage.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Area of stationary object

If planar contacts are used on both fixed and movable sides, then contact area is increased, but contact resistance increases due to point contact when central axes are eccentric

Engineering Contradiction:

Improvecontact areaVSAvoidcontact resistance

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The patent resolves this contradiction by creating an asymmetric contact configuration where the fixed side has a spherical surface and the movable side has a planar surface. This asymmetry ensures that even when central axes are eccentric, the contact maintains a large effective contact area with low contact resistance, avoiding the point contact problem of symmetric planar contacts.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent applies local quality by giving different surface geometries to different parts of the contact system. The fixed side contact surface is spherical to provide a large contact area and low contact resistance, while the movable side contact surface is planar to prevent slippage. This localized differentiation of surface properties optimizes both contact resistance and contact stability.

Inventive Principle:

Principle #3Local quality

3Manufacturing precision

If spherical contacts are used, then contact area is increased reducing contact resistance, but wear and surface damage occur due to slippage

Engineering Contradiction:

Improvecontact resistanceVSAvoidcontact surface durability

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The patent uses asymmetry to prevent the slippage that causes wear and surface damage. By making the movable side contact surface planar while keeping the fixed side spherical, the configuration eliminates relative sliding motion between contacts, thereby preventing wear and surface damage while maintaining low contact resistance through the spherical fixed contact geometry.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The spherical curvature of the fixed side contact provides a large contact area for low contact resistance, while the combination with the planar movable contact prevents slippage-induced wear. The curved surface distributes contact pressure effectively without causing the frictional sliding that leads to surface degradation.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS20250037949A1Vacuum interrupter, vacuum circuit breaker, and vacuum contactor

Publication Date: 2025.01.30 KK TOSHIBA

AI summary

According to one embodiment, a vacuum interrupter includes a vacuum insulation container, a fixed side contact provided in the vacuum insulation container, and a movable side contact provided in the vacuum insulation container and configured to contact and separate from the fixed side contact. A first contact surface of the movable side contact configured to contact the fixed side contact is planar. A second contact surface of the fixed contact configured to contact the movable side contact is spherical protruding toward the movable side contact.