Load Circuit Disconnection Detector Using Temperature Estimation
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Solution Overview
Problem
Conventional disconnection detectors for load circuits require numerous components and detection circuits, leading to increased size and cost.
Innovation Solution
A load circuit disconnection detector that uses a current detector, electronic switch, temperature estimator, and switch controller to detect disconnection by monitoring temperature increases in wires, allowing for a simplified configuration without additional parts, and includes an alarm for notification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional disconnection detectors use current detection circuits or shunt resistors to detect disconnection, then disconnection detection function is achieved, but the number of parts and circuit complexity increases
Solution Approach 1:
The temperature estimation function originally designed for wire temperature monitoring is made multi-functional by also using it for disconnection detection. The same temperature estimator that calculates wire temperature based on current detection is utilized to detect disconnection by checking if temperature remains at initial value, thereby eliminating the need for separate disconnection detection circuits and achieving both temperature monitoring and disconnection detection with a single system
Solution Approach 2:
The patent merges the disconnection detection function into the existing temperature monitoring system. By combining the current detection circuit and temperature estimator used for thermal monitoring with the disconnection detection logic, the system achieves dual functionality without requiring separate detection circuits, shunt resistors, or additional components
2Measurement precision
If conventional disconnection detectors provide separate detection circuits for each load, then accurate disconnection detection is achieved, but the detector size and cost increase
Solution Approach 1:
The temperature estimator is designed to serve multiple purposes: it estimates wire temperature for thermal protection and simultaneously detects disconnection faults. The same calculation mechanism that determines wire temperature based on current magnitude and duration is used to detect whether disconnection has occurred by comparing the estimated temperature against the initial temperature value
Solution Approach 2:
The system uses its own current detection and temperature estimation capabilities to perform disconnection detection without requiring external sensors or additional measurement systems. The temperature estimator leverages the existing current detection data to infer disconnection status, making the system self-sufficient for both temperature monitoring and fault detection
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
Enables efficient detection of disconnection in load circuits with a reduced component count, lowering the size and cost of the detector while providing immediate notification of connection failures.
Implementation Method 1
a temperature estimator for calculating a temperature increase of the wire with a predetermined sampling period based on the current detected by the current sensor
Data Source
Figure 1
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Figure 3(a)~3(d)
AI summary
A load circuit disconnection detector includes: a current sensor (16) for detecting current flowing through a wire (W1) of a load circuit; and a protective device (100) for estimating temperature of the wire (W1) based on the detected current and forcibly turning off a semiconductor switch (Q1) if the estimated temperature of the wire reaches threshold temperature. The load circuit disconnection detector determines that there is a connection failure in the load circuit if a temperature increase calculated by a temperature calculation unit (24) is zero even a predetermined time (P1) after the semiconductor switch (Q1) is turned on.