Capacitor Protection Element with Self-Healing Gas Pressure Activation

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Solution Overview

Problem

Existing protection elements for capacitors with self-healing properties are not always reliable in interrupting electrical current due to inconsistent force application and thermal protection mechanisms, which can lead to incomplete disconnection or sticking issues.

Innovation Solution

A protection element with a membrane that exerts pressure on a current interruption element, utilizing a temperature-sensitive member such as a shape memory alloy spring, wax actuator, or embedded spring to ensure consistent activation of the current interruption element, either through mechanical or thermal means, ensuring reliable overpressure and thermal protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a strong force is applied on the wire connected to a spring to overcome elasticity, then the wire can be broken for current interruption, but the structure becomes more complex and less reliable

Engineering Contradiction:

Improvecurrent interruption reliabilityVSAvoidprotection element structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs a fusible element that is designed to melt and be consumed during the protection event. This disposable approach simplifies the structure by eliminating springs and wires that need to be broken, replacing them with a simple melting element that achieves current interruption through phase change rather than mechanical failure.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent replaces the mechanical wire-breaking system with a thermal-melting system. Instead of using springs and wires that require strong forces to break, the invention uses a fusible element that melts at a predetermined temperature, substituting mechanical force with thermal energy for the current interruption function.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Strength

If the wire is adequately soldered to the membrane, then the connection strength is sufficient, but the wire may still stick to the melted solder and fail to disconnect

Engineering Contradiction:

Improvewire-to-membrane connection strengthVSAvoidwire disconnection reliability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent removes the wire entirely from the membrane structure. The fusible element is positioned separately and melts to interrupt the current without any mechanical connection to the membrane, eliminating the sticking problem that occurs when wires are soldered to membranes.

Inventive Principle:

Principle #2Taking out (Extraction)

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 reliable and consistent mechanism for interrupting electrical current in both overpressure and thermal protection scenarios, ensuring the capacitor is protected against excessive temperature and pressure without incomplete disconnection or sticking issues.

Implementation Method 1

a gas produced upon a self-healing operation occurred within said capacitor... When the pressure raises, the gas present in the housing of the protection element will exert a pressure on the membrane

Methodology Applied

Scientific EffectGas pressure: Pressure Increase

Implementation Method 2

said current interruption element being operationally engaged with a temperature sensitive member provided to react when sensing a temperature increase above a predetermined value

Methodology Applied

Scientific EffectThermal sensing: Temperature Gradient

Implementation Method 3

said temperature sensitive member comprises a spring made of a shape memory alloy, said spring being calibrated at said predetermined temperature value

Methodology Applied

Scientific EffectShape memory effect: Shape Memory Alloy

Implementation Method 4

The thermal protection is realised by using a solder for the connection between the membrane and the wire, which solder will start to melt if the temperature has raised above the predetermined value

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentUS7436646B2Protection element for a capacitor with self-healing properties

Publication Date: 2008.10.14 HITACHI ENERGY LTD

AI summary

A protection element for a capacitor with self-healing properties has a membrane for activating a current interruption element when a gas, produced when a self-healing operation occurs within the capacitor, exerts a pressure on the membrane, the current interruption element being connected in series with an electrode of the capacitor, the current interruption element interrupting an electrical current flowing towards the electrode when the pressure is exerted on the membrane, and the current interruption element being operationally engaged with a temperature sensitive member that reacts, when sensing a temperature above a predetermined value, in a manner to operate the current interruption element.