Overvoltage Protection Element With Center Electrode And Metal Housing
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Solution Overview
Problem
Existing overvoltage protection elements with varistors face issues such as increased leakage current due to aging and transient overvoltages, leading to thermal disconnection which can cause arcs and damage components, and have complex constructions that are costly and unreliable.
Innovation Solution
A temperature-dependent short-circuit switch is integrated within the housing to short-circuit the varistor when a predetermined temperature is reached, preventing overheating and using a center electrode and connecting metals to ensure reliable contact without the need for soldering, and incorporating back-up fuses to isolate the overloaded varistor, reducing impedance and enhancing protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermal disconnection device with separating means is used to disconnect an overheated varistor, then the varistor can be electrically disconnected from the current path, but an arc can occur between the varistor and separating means causing damage to components and the housing
Solution Approach 1:
The patent converts the harmful arc effect into a beneficial one by directing it onto a sacrificial arc contact instead of critical components. The arc contact is specifically designed to absorb arc energy through controlled erosion, protecting the housing and other components from damage while maintaining reliable varistor disconnection functionality
Solution Approach 2:
The arc contact serves as an intermediary element between the varistor and the housing/separating means. It intercepts the arc that occurs during varistor disconnection, transferring the harmful arc energy to itself rather than allowing it to damage critical components or the housing structure
2Reliability
If soldered connections are used to connect varistors to housing halves, then reliable electrical connection is achieved, but the construction becomes complex and costly
Solution Approach 1:
The patent replaces the thermal/mechanical soldering process with a simple mechanical press-fit connection. The housing halves are designed with integrated contact surfaces that directly contact the varistor terminals, eliminating the need for soldered connections while maintaining reliable electrical contact and simplifying the construction process
3Volume of moving object
If varistors are arranged parallel with center electrode between them, then compact design is achieved, but the varistors are susceptible to tolerances particularly in thickness making reliable contact difficult
Solution Approach 1:
The patent introduces elastic spring elements that provide dynamic compensation for thickness tolerances in the varistors. These springs apply continuous contact pressure to ensure reliable electrical connection between the housing halves and varistor terminals, accommodating variations in varistor thickness while maintaining stable contact in the compact parallel arrangement
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
This design minimizes the risk of arcs and component damage, ensures reliable operation, and simplifies construction while maintaining a low impedance connection, thus providing robust and efficient overvoltage protection.
Implementation Method 1
wenn eine vorgeschriebene Grenztemperatur T1 aufgrund einer übermäßigen Erwärmung wenigstens eines Varistors erreicht ist, wenigstens dieser Varistor kurzgeschlossen wird
Implementation Method 2
mit zwei in Reihe geschalteten, gleichgerichteten Varistoren (4, 5) zur Energieableitung von Überspannungsspitzen
Implementation Method 3
eine zentrale Elektrode (6), die wenigstens teilweise zwischen den Varistoren (4, 5) angeordnet ist und mit ihren gegenüberliegenden Seitenflächen mit ersten Anschlussbereichen (9) der Varistoren (4, 5) elektrisch leitend verbunden ist
Implementation Method 4
Die zentrale Elektrode (6) ist von den beiden Gehäusehälften (7, 8) elektrisch isoliert
Data Source
AI summary
The invention relates to an overvoltage protection element, comprising a housing, connections (2, 3) for electrically connecting the overvoltage protection element (1) to the current path or signal path to be protected, two varistors (4, 5) arranged inside the housing and electrically connected in parallel, and a center electrode (6) arranged at least partially between the varistors (4, 5), wherein the housing has two housing halves (7, 8) made of metal and electrically connected to each other, wherein the center electrode (6) is isolated from the housing halves (7, 8) and is electrically connected at the opposite sides of the electrode to a first connection area (9, 10) of a varistor (4, 5), and wherein the two varistors (4, 5) and the center electrode (6) are sandwiched between the two housing halves (7, 8). The overvoltage protection element according to the invention is constructed and can be assembled in a simple and low-cost manner, and has the lowest possible protection level, in that one housing half (8) is designed as a cover, which has a covering section (10) and a recessed engagement section (11), wherein in the installed state of the two housing halves (7, 8) the engagement section (11) engages in the corresponding receiving space (12) formed by the other housing half (7) and the covering section (10) covers the receiving space (12), and in that the two housing halves (7, 8) are designed and can be connected to each other in such a way that in the installed state a visible gap (13) is present between the two housing halves (7, 8), wherein the width (B) of the visible gap (13) varies according to the thickness of the two varistors (4, 5), but the maximum width (B) of the visible gap (13) is less than the corresponding extent of the engagement section (11) of the housing half (8) designed as a cover.