Power Feed Control Device Leakage Detection via Branch Wire Insertion
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Solution Overview
Problem
Conventional power feed control devices fail to accurately detect electrical leakage due to the constant presence of a small unbalanced current caused by the branch wire, leading to potential electrical shock issues.
Innovation Solution
A power feed control device configuration that includes a zero-phase-sequence current transformer and a voltage detection circuit with a branch line inserted in the transformer, allowing for accurate detection of electrical leakage by measuring the sum of currents in the feed line and branch line, and a control circuit that decides on contact welding based on voltage detection results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a branch wire is connected from the voltage detection circuit to ground for detecting contact welding, then contact welding detection capability is improved, but a constant small unbalanced current flows through the zero-phase-sequence current transformer causing false leakage detection
Solution Approach 1:
The patent segments the detection functions by using two separate detection circuits: a voltage detection circuit for contact welding detection and a current-based leakage detection circuit. The voltage detection circuit is disconnected from the zero-phase-sequence current transformer's measurement path, eliminating the interference while preserving contact welding detection capability through alternative voltage-based sensing.
Solution Approach 2:
The patent introduces an intermediary approach by using voltage detection as a separate measurement method that does not interfere with current balance. The voltage detection circuit acts as an intermediary mechanism that provides contact welding detection information without injecting current into the zero-phase-sequence current transformer's measurement path.
2Object-affected harmful factors
If the voltage detection circuit uses a branch wire connected to ground for safety detection, then safety monitoring is improved, but the zero-phase-sequence current transformer cannot accurately distinguish between normal branch current and leakage current
Solution Approach 1:
The patent segments the safety monitoring functions into two independent systems: voltage-based safety monitoring for contact welding detection and current-based leakage detection. This segmentation allows each system to operate independently without interfering with the other's measurement accuracy.
Solution Approach 2:
The patent extracts the voltage detection function from the current measurement path. By taking out the voltage detection circuit's influence from the zero-phase-sequence current transformer's measurement, the system eliminates the interference while preserving safety monitoring capabilities through the separate voltage sensing mechanism.
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 configuration enables precise detection of electrical leakage, preventing electrical shock by accurately distinguishing between normal current imbalances and leakage, thereby ensuring safer operation.
Implementation Method 1
The zero-phase-sequence current transformer ZCT is arranged between the relay 10 and the plug 20, and is passed through by each of the first and second conductive wires L1, L2. The leakage detection circuit 13 is configured to detect occurrence of electrical leakage by detecting an unbalanced current flowing in the feed line (the first conductive wire L1 and the second conductive wire L2) via the zero-phase-sequence current transformer ZCT. If unbalance occurs in currents flowing in the feed line (the first conductive wire L1 and the second conductive wire L2), the zero-phase-sequence current transformer ZCT generates an induced current according to the unbalanced current.
Data Source
AI summary
A branch wire L5 from the voltage detection circuit 14 is inserted in the zero-phase-sequence current transformer ZCT in the direction from the load side to the external power supply side. For this configuration, the zero-phase-sequence current transformer ZCT is to detect unbalance of the sum of current flowing in the first and second conductive wires L1, L2 and the current flowing in the branch wire L5. Therefore, the present invention can accurately detect occurrence of electrical leakage.