Load Control Apparatus Using Thermal Switch for Overcurrent Detection
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Solution Overview
Problem
Existing load control apparatuses for detecting overcurrents in electric conductor elements are complex and expensive due to the need for multiple temperature sensors integrated into the load current circuit.
Innovation Solution
A load control apparatus that uses temperature-sensitive switch members connected heat-conductively but electrically isolated from the load current circuit, allowing overcurrent detection without interfering with the circuit operation and reducing design and manufacturing costs by using series-connected, normally closed or open type switch members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature sensors are integrated into the load current circuit for overcurrent detection, then overcurrent detection capability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent introduces a temperature-sensitive switch member as an intermediary element that is thermally coupled to the load current circuit but electrically isolated from it. This mediator detects temperature changes caused by overcurrent through thermal conduction while avoiding direct electrical contact, thus simplifying the circuit structure and reducing complexity while maintaining reliable overcurrent detection capability
Solution Approach 2:
The patent replaces the electronic temperature sensing system with a thermomechanical system using temperature-sensitive switch members that change their mechanical state (open/close) in response to temperature changes. This substitution eliminates complex electronics and signal processing circuits, thereby reducing device complexity and manufacturing cost while preserving overcurrent detection functionality
2Reliability
If temperature sensors are integrated into the load current circuit, then overcurrent detection is achieved, but manufacturing cost increases
Solution Approach 1:
The patent employs temperature-sensitive switch members that are simple, inexpensive components compared to integrated temperature sensors. These switch members can be basic thermal switches or PTC thermistors that are cheap to manufacture and replace, significantly reducing the overall manufacturing cost while maintaining effective overcurrent detection capability
Solution Approach 2:
The patent extracts the temperature-sensitive detection function from the electrical circuit domain and places it in the thermal domain using separate temperature-sensitive switch members. This extraction allows the use of simpler, cheaper components that are not constrained by electrical circuit requirements, thereby reducing manufacturing cost while preserving detection reliability
3Measurement precision
If temperature-sensitive components are part of the load current circuit, then direct temperature measurement is possible, but the components must endure high load currents
Solution Approach 1:
The patent uses thermally conductive but electrically insulating materials or structures as intermediaries to transfer heat from the load current circuit to the temperature-sensitive switch members. This intermediary approach allows the temperature-sensitive components to accurately sense temperature changes caused by overcurrent without being exposed to the high current stresses, thereby preserving measurement precision while eliminating the need for high current endurance
Solution Approach 2:
The patent segments the detection system into two separate functional parts: the load current circuit and the temperature detection circuit. The temperature-sensitive switch members are placed in a separate control current circuit that is thermally coupled but electrically isolated from the load current circuit. This segmentation allows each part to be optimized independently, enabling precise temperature measurement without requiring the temperature-sensitive components to withstand high load currents
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 simplifies the detection of overcurrents while maintaining circuit operation integrity and reducing costs, as the temperature-sensitive switch members are not part of the load current circuit, thus not requiring endurance to load currents, and can be made more sensitive with thermistor assemblies.
Implementation Method 1
The temperature-sensitive switch member S is connected heat-conductively to the electric conductor element 4
Implementation Method 2
The temperature-sensitive switch member S is capable of changing its operational state in response to an increase in the temperature to a predetermined value
Data Source
AI summary
A load control apparatus adapted to indirectly detect an overcurrent, i.e. a current magnitude exceeding a predetermined limit value, occurring in an electric conductor element (4) belonging to a load current circuit (20), on the basis of an increase in temperature. The load control apparatus (30) comprises a control current circuit including a temperature-sensitive switch member (S) capable of changing its operational state in response to an increase in the temperature to a predetermined value, and a control unit (32) adapted to detect a change in the operational state of the temperature-sensitive switch member (S), and to detect an overcurrent occurring in the electric conductor element (4) based thereon, the temperature-sensitive switch member (S) being adapted to be connected heat-conductively to a target element, in which at least part of the load current of the electric conductor element (4) passes in an operating situation, and the temperature-sensitive switch member (S) being further adapted to be electrically insulated from the electric conductor element (4) of the load current circuit.