Electric Wire Protection Device Using Thermal Calculation
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Solution Overview
Problem
Conventional electric-wire protection devices may delay the timing of shutting off energization if the estimated temperature of the electric wire falls below the actual temperature, necessitating improved temperature estimation and protection methods.
Innovation Solution
An electric-wire protection device with a voltage adjustment unit and a controller that calculates temperature information based on current values and initial temperature values, shifting into a shut-off state when temperatures exceed thresholds and entering a sleep state when temperatures drop below initial values, ensuring accurate protection by using a semiconductor relay and microcomputer-based control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the controller continuously calculates temperature information and remains in active state, then the temperature estimation accuracy is improved, but the power consumption increases
Solution Approach 1:
The controller alternates between active state (performing temperature calculation) and sleep state (suspending temperature calculation). Temperature information is calculated periodically based on current values when in active state, and the controller transitions to sleep state when temperature is below threshold, thereby reducing power consumption while maintaining temperature monitoring capability.
2Reliability
If the initial temperature value is set to ambient temperature, then the calculation starts from a low baseline, but the estimated temperature may fall below actual temperature causing delayed shut-off
Solution Approach 1:
Before starting temperature calculation, the controller pre-heats the initial temperature value to a predetermined temperature that is higher than ambient temperature. This preliminary action ensures that the estimated temperature does not fall below the actual temperature during the calculation process, preventing delayed shut-off timing and improving protection reliability.
3Use of energy by moving object
If the controller enters sleep state to reduce power consumption, then energy efficiency is improved, but temperature monitoring may be insufficient
Solution Approach 1:
The controller uses feedback from temperature information and current values to determine state transitions. When temperature information calculated from current values indicates safe operating conditions, the controller enters sleep state to reduce power consumption. When temperature exceeds threshold or abnormal conditions are detected, the controller wakes up to perform monitoring, thereby balancing power savings with reliable temperature monitoring.
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 device effectively protects electric wires by ensuring timely shut-off based on accurate temperature calculations, preventing excessive heating and reducing power consumption by suspending temperature calculations during sleep states.
Implementation Method 1
calculates the temperature rise due to the arc and further, when the current flowing through the load is zero or is decreasing, calculates the fall in temperature of the electric wire based on the thermal characteristics of the electric wire
Implementation Method 2
calculates the rise in temperature of an electric wire based on the thermal characteristics (thermal resistance and thermal capacity) of the electric wire
Data Source
AI summary
An electric-wire protection device includes a voltage adjustment unit that adjusts the voltage to a load, and a controller that includes a temperature calculation unit that calculates temperature information on an electric wire from a value of current, and makes the voltage adjustment unit into a shut-off state based on the temperature information. The temperature information is calculated from an amount of temperature changes based on the current value and a predetermined initial value. The controller shifts into a sleep state when a sleep condition is satisfied that includes a condition that the temperature information is lower than the initial value. The initial value when the controller returns from the sleep state is based on a convergence value of temperature in conducting energization on the electric wire at a maximum value of steady-state current.