Multi-winding Ground Fault Sensor with Switched Injection Winding
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Solution Overview
Problem
Traditional dual function arc fault and ground fault circuit breakers require two current sensors and signal chains, leading to increased component space and cost, particularly in miniature circuit breakers.
Innovation Solution
A single coil-based current sensor with concentric overlapping windings and a switching element allows for both load current and differential current measurement using a single sensor, eliminating the need for two sensors and signal chains by selectively switching the injection winding in and out of the detection signal chain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two current sensors are used for arc fault and ground fault detection, then detection functionality is complete, but component space and cost increase
Solution Approach 1:
The patent combines arc fault detection and ground fault detection into a single current sensor by integrating two windings (first winding for arc fault, second winding for ground fault) on one core, eliminating the need for two separate sensors and reducing component space
Solution Approach 2:
The single current sensor performs multiple functions by using different windings for different detection purposes - the first winding detects arc faults while the second winding detects ground faults, making one sensor universal for both protection functions
2Reliability
If two current sensors are used for arc fault and ground fault detection, then detection functionality is complete, but device complexity and cost increase
Solution Approach 1:
The patent merges two separate signal chains into one by processing outputs from both windings through a single signal chain with a multiplexer that selectively routes signals for arc fault or ground fault detection, reducing device complexity
Solution Approach 2:
The single signal chain is designed to be universal by incorporating a multiplexer that can handle both arc fault detection signals and ground fault detection signals, eliminating the need for separate dedicated signal chains
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 enables smaller, cost-effective implementation of dual function miniature circuit breakers by minimizing space and reducing components, while maintaining effective arc fault and ground fault detection capabilities.
Implementation Method 1
a current transformer for measuring current
Implementation Method 2
current from the line conductor can be selectively switched into the injection winding thereby inducing flux into the sense winding
Data Source
AI summary
A single current transformer arc fault/ground fault sensing circuit utilizes a sense coil and an injection coil from the line conductor placed concentrically and overlapping on a common core. The injection coil is operated by an in-line switch to allow current flow into the injection winding to influence the sense coil. With both the line and return conductors of a single phase circuit being surrounded by the transformer, opening the switch allows a ground fault sampling period, while closing the switch allows an arc fault sampling period.