Circuit Interrupter Temperature Compensation Trip Time
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Solution Overview
Problem
Circuit interrupters, such as circuit breakers, face challenges in detecting low overcurrent conditions due to ambient temperature effects, where cold temperatures can prevent bimetal strips from tripping even when a fault is present, leading to potential damage from persistent high temperature conditions.
Innovation Solution
A circuit interrupter that incorporates a current sensor, a temperature sensor, and a processor to select a trip time based on sensed current and adjust it according to sensed temperature, ensuring timely tripping of separable contacts, thereby compensating for ambient temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bimetal strip is used for thermal protection in cold ambient temperatures, then the circuit breaker may fail to trip during low overcurrent conditions, but the device complexity increases with temperature compensation mechanisms
Solution Approach 1:
The patent replaces the purely mechanical bimetal strip thermal protection system with an electronic sensing and processing system. Current sensors detect overcurrent conditions, temperature sensors monitor ambient temperature, and a processor calculates adjusted trip times based on both current magnitude and temperature compensation factors, eliminating reliance on mechanical bimetal strip behavior in varying temperatures
Solution Approach 2:
The patent introduces a processor as an intermediary between the sensing elements and the trip mechanism. The processor receives data from current and temperature sensors, performs calculations to determine appropriate trip times with temperature compensation, and controls the trip mechanism accordingly, serving as a mediator that integrates multiple sensing inputs to make intelligent tripping decisions
2Reliability
If the trip time is extended to allow bimetal strip heating in cold temperatures, then false trips increase, but protection reliability decreases allowing damage from prolonged high temperature
Solution Approach 1:
The patent performs preliminary temperature assessment before determining trip time. The temperature sensor measures ambient temperature in advance, and the processor uses this information to pre-calculate the appropriate trip time adjustment factor, allowing the system to respond appropriately to overcurrent conditions regardless of whether the environment is cold or hot
Solution Approach 2:
The patent implements dynamic trip time adjustment based on real-time temperature measurements. Rather than using fixed trip times or simple thermal accumulation, the system continuously monitors temperature and dynamically adjusts the trip time calculation to compensate for ambient temperature effects, enabling adaptive protection that responds to changing environmental conditions
3Measurement precision
If temperature compensation is added to the circuit interrupter, then the trip accuracy improves, but the device complexity increases
Solution Approach 1:
The patent implements a processor-based control system that performs multiple functions: detecting overcurrent conditions, measuring ambient temperature, calculating temperature compensation factors, determining appropriate trip times, and controlling the trip mechanism. This multi-functional approach consolidates what would otherwise require separate mechanisms into a single intelligent control unit
Solution Approach 2:
The patent replaces complex mechanical temperature compensation mechanisms with electronic sensing and computational processing. Instead of using additional mechanical elements like pre-heating coils or mechanical linkages to compensate for temperature effects, the system uses temperature sensors and processor-based calculations to achieve the same compensation effect with greater precision and less mechanical complexity
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 solution effectively detects and responds to low overcurrent conditions by adjusting the trip time based on temperature, preventing damage from prolonged high temperature conditions and ensuring reliable protection against faults.
Implementation Method 1
a current sensor structured to sense a current flowing through the protected circuit
Implementation Method 2
a temperature sensor structured to sense a temperature of the protected circuit proximate the current sensor
Implementation Method 3
Current in the protected circuit flows through the bimetal strip. Increasing current flowing through the bimetal strip causes the bimetal strip to heat up and bend
Implementation Method 4
causes the bimetal strip to heat up and bend
Data Source
AI summary
A circuit interrupter for protecting a protected circuit includes separable contacts, an operating mechanism structured to trip open the separable contacts, a current sensor structured to sense a current flowing through the protected circuit, a temperature sensor structured to sense a temperature of the protected circuit proximate the current sensor, and a processor configured to select a trip time based on the sensed current, to adjust the selected trip time based on the sensed temperature, and to cause the operating mechanism to trip open the separable contacts when the adjusted selected trip time is reached.