Back-to-Back JFET Switching for Arc-Free Fault Interruption

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Solution Overview

Problem

Conventional electrical switching devices are slow, generate electrical arcs during current interruption, and have high electrical resistance, leading to wear and complex configurations.

Innovation Solution

An electrical switching device using back-to-back normally conducting JFET transistors and a control module for rapid current interruption, with a switching device that defaults to a non-conducting state, eliminating the need for arc-extinguishing chambers and reducing electrical resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If mobile contacts are used for current interruption, then galvanic isolation and protection are achieved, but switching speed is slow and electrical arcs occur causing wear

Engineering Contradiction:

Improveprotection levelVSAvoidswitching speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent replaces the mechanical mobile contact system with an electronic transistor-based switching system. The transistor acts as an electronic switch that can open and close circuits rapidly without mechanical movement, eliminating arc-related wear while maintaining electrical isolation through the transistor's off-state. This substitution of mechanical components with electronic components directly resolves the contradiction between reliability (protection) and switching speed.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Speed

If non-conducting by default transistors are used, then faster current interruption is achieved, but electrical resistance is high causing significant losses

Engineering Contradiction:

Improvecurrent interruption speedVSAvoidelectrical losses

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent inverts the traditional transistor default state from non-conducting to normally conducting. By using normally conducting transistors that are kept in the on-state during normal operation, the system achieves low electrical resistance and minimal power losses. The transistor is rapidly switched to the off-state only when current interruption is required, thus maintaining low energy losses while preserving fast switching capability when needed.

Inventive Principle:

Principle #13The other way round (Inversion)

3Loss of energy

If normally conducting transistors are used, then low electrical resistance is achieved, but the device cannot maintain protection without power

Engineering Contradiction:

Improveelectrical resistanceVSAvoidprotection without power

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent implements a control system that continuously maintains the transistor in the on-state through preliminary action (continuous control signaling). This active control ensures that the transistor remains in the low-resistance conducting state during normal operation. When a fault is detected, the control system rapidly switches the transistor to the off-state, and the system can maintain this protective off-state even without continuous power, as the transistor's default off-state provides the necessary isolation and protection.

Inventive Principle:

Principle #10Preliminary action

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 enables fast current interruption without electrical arcs, maintains protection even without power, and reduces device wear, while maintaining low electrical resistance.

Implementation Method 1

unifying a first electrical signal supplied to a gate of the at least two first transistors, the circuit comprising, in series, at least two first back-to-back normally conducting JFET transistors

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

at least two first back-to-back normally conducting JFET transistors and at least one switching device

Methodology Applied

Scientific EffectField effect transistor operation:

Data Source

PatentUS12525784B2Electrical switching device, and associated switching system and method

Publication Date: 2026.01.13 SCHNEIDER ELECTRIC IND SAS

AI summary

A switching device, a switching module and a control module configured to command the interruption of a current by way of the switching module in the event of a fault. The switching module includes a circuit carrying the current and including, in series, two back-to-back depletion-mode JFETs and a switching component that switches between two configurations. The switching component allows the current to flow in one configuration and prevents the current from flowing in the other configuration, which it is in by default. The control module generates a first signal for keeping the switching component in the first configuration, the control module being configured, in the event of a fault, to generate a second signal for commanding the interruption of the current by way of a transistor, and configured to interrupt the first signal in the event of a fault.