Electric Wire Protection Device Using Dynamic Time Constants
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Solution Overview
Problem
Conventional electric wire protection devices may delay the timing for interrupting energization when the estimated temperature of the electric wire is lower than the actual temperature, leading to inadequate protection.
Innovation Solution
An electric wire protection device that includes a voltage adjuster and a controller, which calculates temperature information based on current values and adjusts time constants to ensure accurate temperature estimation, using a first time constant larger than the actual time constant of the electric wire during interruption and a second time constant smaller than the actual time constant during power supply to prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single time constant is used for temperature calculation, then the calculation is simple, but the temperature estimation accuracy deteriorates when switching between power supply and interruption states
Solution Approach 1:
The patent applies dynamics by switching between two different time constants (first time constant during interruption state, second time constant during power supply state) based on the operational state of the voltage adjuster. This dynamic adaptation allows the temperature calculation to accurately reflect the actual thermal behavior of the electric wire in each state, resolving the contradiction between simplicity and accuracy.
Solution Approach 2:
The patent changes the time constant parameter according to the operational state (interruption or power supply). By setting the first time constant to be equal to or larger than the actual time constant during interruption, and the second time constant to be smaller than the actual time constant during power supply, the system maintains accurate temperature estimation without excessive complexity.
2Reliability
If the estimated temperature is lower than actual temperature, then the protection timing is delayed, but using a smaller time constant may cause premature protection
Solution Approach 1:
The patent performs preliminary action by setting the first time constant to be equal to or larger than the actual time constant before the interruption occurs. This ensures that the estimated temperature does not fall below the actual temperature, allowing the protection system to trigger at the appropriate time without delay, thus improving reliability without excessive time loss.
Solution Approach 2:
The system uses feedback by continuously monitoring the operational state (interruption or power supply) and adjusting the time constant accordingly. This feedback mechanism ensures that the temperature estimation remains synchronized with actual thermal conditions, preventing both delayed and premature protection triggering.
3Reliability
If a larger time constant is used during interruption, then the temperature estimation is more conservative (higher), but the response to actual temperature changes is slower
Solution Approach 1:
The patent applies dynamics by using a larger first time constant during interruption state to maintain conservative (higher) temperature estimates for safety, while switching to a smaller second time constant during power supply state to improve response speed to actual temperature changes. This dynamic switching resolves the contradiction between reliability and response speed.
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 ensures timely and effective protection of the electric wire by maintaining an estimated temperature higher than the actual temperature, preventing excessive heat rise and ensuring safe operation.
Implementation Method 1
calculates temperature information of an electric wire which connects a power source with the load based on a current value flowing through the voltage adjuster
Data Source
AI summary
An electric wire protection device includes a voltage adjuster that adjusts voltage on a power source side to be supplied to a load and a controller that includes a temperature calculation part which calculates temperature information of an electric wire based on a current value flowing through the voltage adjuster. The controller sets a first time constant as a time constant used to calculate the temperature information while the voltage adjuster is in the interrupted state, and sets a second time constant as a time constant used to calculate the temperature information while the voltage adjuster supplies power to the load. The first time constant is a value larger than the second time constant and equal to or larger than an actual time constant of the electric wire, and the second time constant is a value smaller than the actual time constant of the electric wire.