Electrical Apparatus Overcurrent Detection via Current Threshold
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Solution Overview
Problem
At construction sites, the use of multiple electrical apparatuses connected to a power supply leads to increased power consumption and overcurrent issues, causing circuit breakers to actuate, which can result in reduced work efficiency and failure of air compressors due to unnoticed voltage drops from extension cords, making it difficult to distinguish between voltage drops from multiple devices and those from cord length variations.
Innovation Solution
An electrical apparatus with a drive unit, voltage detection unit, and control unit that sets a threshold value based on power supply voltage variations to determine when a circuit breaker should be actuated, excluding external factors like cord resistance, allowing for accurate detection of overcurrents and preventing unnecessary interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If extension cord is used to connect electrical apparatus to power supply, then flexibility of installation is improved, but voltage drop occurs causing false detection of overcurrent
Solution Approach 1:
The patent replaces voltage threshold comparison with current detection by substituting the mechanical/electrical voltage measurement system with a current detection system. The control unit detects current flowing through the drive unit and compares it with a threshold value, eliminating the influence of extension cord resistance on the protection mechanism.
Solution Approach 2:
The patent introduces current detection as an intermediary parameter between the electrical apparatus and the protection mechanism. Instead of directly monitoring voltage at the apparatus, the system uses current flow as an intermediate indicator that is not affected by extension cord resistance, providing accurate overcurrent protection regardless of installation conditions.
2Device complexity
If voltage threshold comparison method is used to detect overcurrent, then simplicity of control is improved, but false detection occurs due to extension cord resistance
Solution Approach 1:
The patent substitutes the voltage-based control mechanism with a current-based control mechanism. By detecting current flow and comparing it with a threshold, the system maintains simplicity while eliminating false detections caused by extension cord resistance, as current measurement is not influenced by the resistance of connecting cables.
Solution Approach 2:
The patent changes the monitored parameter from voltage to current. This parameter change fundamentally resolves the issue of false detection, as current flow through the drive unit directly reflects the actual load condition without being affected by extension cord resistance, while maintaining comparable control simplicity.
3Productivity
If multiple electrical apparatuses are operated simultaneously, then productivity is improved, but overcurrent causes circuit breaker actuation reducing work efficiency
Solution Approach 1:
The patent implements a feedback mechanism where the control unit continuously monitors current flow and compares it with a predetermined threshold. When the current exceeds the threshold, the control unit stops the drive unit, preventing circuit breaker actuation. This feedback loop enables multiple apparatuses to operate simultaneously without causing work interruptions.
Solution Approach 2:
The patent performs preliminary current detection and comparison before the circuit breaker can actuate. By detecting overcurrent conditions in advance and stopping the drive unit proactively, the system prevents circuit breaker tripping and eliminates work interruptions, allowing continuous operation of multiple apparatuses.
Data Source
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AI summary
An electrical apparatus is connected to a power supply and changes operation in accordance with variation of a power supply voltage of the power supply in accordance with drive of another electrical apparatus connected to the same power supply. The electrical apparatus includes a drive unit driven by the power supply, a voltage detection unit, a current detection unit, and a control unit which sets a threshold value with which a circuit breaker which breaks the power supply is not driven, based on (i) a power supply voltage of the power supply detected by the voltage detection unit when the drive unit is driven, (ii) a power supply voltage of the power supply detected by the voltage detection unit when the drive unit is not driven, and (iii) a current detected by the current detection unit when the drive unit is driven.