Leakage Current Protection Device Using Voltage-Controlled MOSFET Switch

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Solution Overview

Problem

Existing devices for protecting against leakage currents are either bulky, unreliable, costly, or not 'fail-safe', and they often require significant adaptation and power supply, posing risks of component destruction and inadequate protection against contact voltages.

Innovation Solution

A compact device using a switch controlled by the voltage of an electrical connection to divert current, eliminating the need for electromechanical relays or capacitors, with a MOSFET transistor and limiting circuit to manage current flow, ensuring 'fail-safe' operation and compliance with safety standards.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a capacitor is used between the output of a breaker and the electrical earth to limit AC leakage currents, then leakage currents are limited, but the device requires a significant area and requires adaptation of the capacitor value for each type of breaker and application

Engineering Contradiction:

Improveleakage currentsVSAvoiddevice area

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The patent replaces the passive capacitor-based solution with an active electronic circuit comprising a semiconductor switch (MOSFET), control circuit, and associated components. This substitution enables more compact integration and eliminates the need for large-capacitor physical space while maintaining leakage current limitation functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention uses a controllable semiconductor switch whose resistance can be dynamically adjusted between low and high states based on control signals. This parameter change capability allows the device to adapt to different breaker types and applications without requiring physical adaptation of capacitor values, thereby reducing both area and adaptation complexity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If electromechanical relays are used in series with a semi-conducting breaker, then perfect galvanic isolation and fail-safe protection are obtained, but the device requires significant area, significant weight, is very unreliable, and has significant cost

Engineering Contradiction:

Improveprotection reliabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces electromechanical relays with solid-state semiconductor switches (MOSFETs) and electronic control circuits. This substitution eliminates mechanical moving parts, thereby improving reliability, reducing weight, decreasing device complexity, and lowering cost while maintaining the fail-safe protection functionality through electronic control mechanisms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The control circuit is designed to automatically detect breaker state changes and control the semiconductor switch accordingly without requiring external intervention. The system monitors itself and responds autonomously to maintain protection, reducing the need for complex external control mechanisms while ensuring reliable operation.

Inventive Principle:

Principle #25Self-service

3Object-affected harmful factors

If a secondary breaker is disposed between the output of a primary breaker and the earth, then leakage current protection is achieved, but risks of destruction of components due to simultaneous closing of the two breakers are created, and a power supply is required to operate

Engineering Contradiction:

Improveleakage currentsVSAvoidcomponent safety

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent incorporates a control circuit that monitors the state of the primary breaker and uses this feedback information to control the semiconductor switch. The control circuit detects when the primary breaker opens and responds by controlling the secondary path, preventing simultaneous closing scenarios that could cause component destruction. This feedback mechanism ensures safe operation without requiring additional power supply beyond what is already available in the system.

Inventive Principle:

Principle #23Feedback

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 effectively limits leakage currents and contact voltages, providing reliable protection against electrical risks, including lightning strikes, while being compact and adaptable to various applications without the need for electromechanical relays or capacitors.

Implementation Method 1

a switch configured so as to at least partially divert the current flowing in the first electrical connection and controlled by the voltage of the first electrical connection

Methodology Applied

Scientific EffectMOSFET transistor operation:

Implementation Method 2

controlled by the voltage of the first electrical connection... if a voltage occurs on the first electrical connection, then it is possible to use this voltage to close said switch

Methodology Applied

Scientific EffectVoltage-controlled switching:

Data Source

PatentUS10224711B2Device and method for protecting against leakage currents

Publication Date: 2019.03.05 SAFRAN ELECTRICAL & POWER

AI summary

Device for protecting against leakage currents, the device being intended to be wired up between a first electrical connection (2) and a second electrical connection (3). The device comprises a switch (5) configured so as to at least partially divert the current flowing in the first electrical connection and controlled by the voltage of the first electrical connection.