Circuit Breaker Varistor Segmentation for Voltage Reduction

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Solution Overview

Problem

The existing circuit-breakers require semiconductor switches with high breakdown voltages due to the logarithmic I-V characteristics of metal oxide varistors, leading to increased conduction losses, size, and cost, as well as thermal runaway issues at low voltages.

Innovation Solution

Incorporating a controllable switching component in series with the varistor device in the switching circuit, allowing for the use of lower voltage clamping varistors and reducing the breakdown voltage requirements of semiconductor switches, and utilizing a separation switching unit to manage current and voltage peaks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a varistor device is used in the switching circuit, then overvoltage protection is provided, but semiconductor switches with large breakdown voltage are required resulting in increased conduction losses

Engineering Contradiction:

Improveovervoltage protectionVSAvoidconduction losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The switching circuit is divided into two parallel current paths: a first current path with the varistor device for overvoltage protection, and a second current path with semiconductor switches for controlled switching. This segmentation allows each component to operate in its optimal voltage range, reducing conduction losses while maintaining protection functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first current path with the varistor device acts as an intermediary protection path that handles overvoltage conditions, allowing the semiconductor switches in the second current path to use lower breakdown voltages. The varistor clamps voltage spikes, protecting the semiconductor switches from requiring high breakdown voltage ratings.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a varistor device is used in the switching circuit, then overvoltage protection is provided, but the size and cost of semiconductor switches increase

Engineering Contradiction:

Improveovervoltage protectionVSAvoidsize of semiconductor switches

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The circuit is segmented into two parallel paths, allowing the semiconductor switches to be sized for lower voltage applications while the varistor handles high voltage protection, thereby reducing the physical size of the semiconductor components.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The varistor device serves as an intermediary that absorbs and dissipates overvoltage energy, preventing the semiconductor switches from needing to be oversized to handle voltage spikes, thus reducing their required size and cost.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If semiconductor switches with large breakdown voltage are used, then overvoltage protection is ensured, but the cost of the circuit-breaker increases

Engineering Contradiction:

Improveovervoltage protectionVSAvoidcost of circuit-breaker

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The circuit is segmented into two parallel paths, allowing the use of lower-cost semiconductor switches with smaller breakdown voltages in the second current path, while the varistor device in the first current path provides the necessary overvoltage protection, thereby reducing overall system cost.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The varistor device serves as a cost-effective intermediary that provides overvoltage protection, allowing the use of cheaper semiconductor switches with lower breakdown voltage ratings, thus reducing the overall cost of the circuit-breaker while maintaining protection functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration reduces the breakdown voltage requirements of semiconductor switches by half, minimizing conduction losses and preventing thermal runaway, while also eliminating arcing during switch operations and reducing the overall size and cost of the circuit-breaker.

Implementation Method 1

The varistor dissipates almost 99% of its energy as heat and increases its voltage to stop the current flow in the circuit-breaker

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

the switching circuit comprises a varistor device and a controllable switching component, the varistor device and the controllable switching component being connected in series between the first and the second current path

Methodology Applied

Scientific EffectElectrical conduction control: Conduction (electrical)

Data Source

PatentUS11295919B2Circuit-breaker with reduced breakdown voltage requirement

Publication Date: 2022.04.05 EATON INTELLIGENT POWER LTD

AI summary

A circuit-breaker includes: an input terminal for connecting the circuit-breaker to a voltage source; an output terminal for connecting t the circuit-breaker to a load; a switching circuit having an input side connected to the input terminal and having an output side; and a separation switching unit connected to the output terminal and to the output side of the switching circuit. The switching circuit includes a first current path and a second current path, the first and the second current path being connected in parallel between the input side and the output side. The switching circuit includes a varistor device and a controllable switching component, the varistor device and the controllable switching component being connected in series between the first and the second current path.