Varistor Shutter Release for Orientation-Independent Disconnection

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Solution Overview

Problem

Existing varistor components with meltable material fuses cannot guarantee a reliable electrical disconnection under abnormal operation conditions, especially in varying orientations and accelerations, leading to potential electrical contact and increased risk of fire.

Innovation Solution

A varistor component with an active releasing device featuring a heat-sensitive element and shutter, which actively closes the path between the varistor and external contact under abnormal conditions, ensuring a consistent and rapid electrical disconnection independent of the fuse material's position, using a heat-sensitive element with a melting point between 185°C and 230°C, and a spring to drive the shutter, ensuring galvanic isolation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a meltable material fuse is used to open the circuit under abnormal conditions, then the circuit can be opened to prevent further damage, but the reliability of electrical disconnection is insufficient due to unknown material flow direction under acceleration and varying orientations

Engineering Contradiction:

Improveelectrical disconnection reliabilityVSAvoidsafety mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A shutter is introduced as an intermediary component between the heat-sensitive element and the external contact. The shutter actively moves to close the path and prevent electrical contact, mediating the safety function more reliably than passive fuse material flow alone. This resolves the contradiction by providing positive action rather than relying on unpredictable material flow.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The shutter is pre-positioned and actively driven to close the path before the fuse material can flow unpredictably. By taking preliminary action to establish the open circuit state through shutter movement, the system ensures reliable disconnection regardless of subsequent material flow behavior under acceleration or orientation changes.

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If the varistor component relies on gravitational energy for fuse material flow, then the structure can be simple, but the functionality is compromised under varying orientations and accelerations

Engineering Contradiction:

Improveorientation independenceVSAvoidelectrical disconnection guarantee

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The passive gravitational field is replaced with an active mechanical driving system (spring) that positively drives the shutter to close the path. This substitution eliminates dependence on gravitational orientation, ensuring the shutter can reliably move to establish electrical disconnection under any orientation or acceleration condition.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system transitions from a static, gravity-dependent fuse mechanism to a dynamic, actively driven shutter system. The shutter can respond and move to close the path under any orientation or acceleration, providing orientation-independent functionality while maintaining high reliability of electrical disconnection.

Inventive Principle:

Principle #15Dynamics

3Speed

If a heat-sensitive element with melting point between 185°C and 230°C is used, then the response time under abnormal conditions is improved, but the risk of premature activation under normal operation must be controlled

Engineering Contradiction:

Improveresponse speed under abnormal conditionsVSAvoidfalse activation resistance

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The melting point parameter of the heat-sensitive element is specifically selected within the range of 185°C to 230°C. This parameter optimization enables rapid response to abnormal overtemperature conditions while maintaining stability during normal operation at lower temperatures, achieving both fast response speed and resistance to false activation.

Inventive Principle:

Principle #35Parameter changes

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 significantly reduces the risk of electrical power dissipation and potential fire by ensuring a reliable open circuit under abnormal conditions, with a guaranteed response time and functionality in any position, independent of gravitational energy or material flow.

Implementation Method 1

the heat-sensitive element is provided and electrically connected to the varistor and to the second external contact. The heat-sensitive element has a melting point between 185°C and 230°C

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

a spring to drive the shutter, ensuring galvanic isolation

Methodology Applied

Scientific EffectElastic potential energy conversion to kinetic energy: Spring

Data Source

PatentEP3443568B1Varistor component and method for securing a varistor component

Publication Date: 2023.10.18 TDK ELECTRONICS AG

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AI summary

A varistor component (VC) with improved failure safety is provided. The varistor component (VC) comprises a varistor (V) and a second external contact (EC2). A current path (P) between the varistor (V) and a second external contact (EC2) can be actively blocked by a shutter (SH) if the temperature of a heat-sensitive element (HSE) exceeds a critical temperature.