AC/DC Leakage Detection Using Magnetic Modulation and Time-Sharing
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Solution Overview
Problem
Conventional AC-type leakage protectors are unable to detect DC leakage current and high-frequency leakage currents, posing safety risks as they do not provide comprehensive protection against all types of residual currents.
Innovation Solution
A method utilizing an H-bridge driving module to excite a magnetic core for bidirectional detection of DC and low-frequency AC currents, with signal processing through AD conversion, synchronization, demodulation, and FFT analysis to detect DC, low-frequency, and high-frequency AC leakage currents, enabling time-sharing detection and overall residual current calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If AC-type leakage protectors are used, then AC leakage current detection is achieved, but DC leakage current and high-frequency leakage current cannot be detected
Solution Approach 1:
The detection system is divided into three independent detection channels: DC detection channel, low-frequency AC detection channel, and high-frequency AC detection channel. Each channel uses dedicated signal processing paths and detection circuits to detect specific frequency ranges, enabling comprehensive coverage of all leakage current types while maintaining specialized optimization for each detection task
Solution Approach 2:
The leakage protection device integrates multiple detection functions into a single system. The control circuit can selectively activate different detection channels based on the detected signal characteristics, making the device capable of detecting DC, low-frequency AC, and high-frequency AC leakage currents, thereby providing universal protection against all types of leakage currents
2Adaptability or versatility
If bidirectional excitation is applied to the magnetic core, then DC and low-frequency AC currents can be detected, but the magnetic core enters saturation region requiring complex signal processing
Solution Approach 1:
The system uses periodic square wave excitation signals to drive the magnetic core, creating regular saturation cycles during DC detection. This periodic action allows the use of synchronous detection techniques where the detection signal is sampled at specific phases of the excitation cycle, enabling accurate DC current measurement while rejecting harmonics and noise through synchronized signal processing
Solution Approach 2:
The control circuit dynamically switches between different detection modes (DC detection mode, low-frequency AC detection mode, high-frequency AC detection mode) based on the detected signal characteristics. The H-bridge circuit dynamically adjusts its operation to provide bidirectional excitation during DC detection or pure induction mode during AC detection, optimizing performance for each detection task
3Adaptability or versatility
If time-sharing detection is used for DC and AC currents, then comprehensive leakage detection is achieved, but detection response time is extended
Solution Approach 1:
The system employs periodic square wave excitation for DC detection and uses synchronous sampling techniques where measurements are taken at specific phases of the excitation cycle. This allows rapid alternation between DC and AC detection channels with minimal transition time, as each channel is activated only during its designated time slot in a repeating cycle
Solution Approach 2:
The control circuit continuously monitors the input signal and predicts when leakage currents are likely to occur based on operational patterns. Detection resources are pre-positioned and can be rapidly activated when leakage is detected, reducing the effective response time compared to waiting for the next scheduled detection cycle
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
Effectively detects DC and AC leakage currents, including low-frequency and high-frequency components, providing enhanced safety protection by identifying sudden current increases and switching detection modes accordingly.
Implementation Method 1
bidirectional excitation is applied to a magnetic core to make the magnetic core enter a saturation region
Implementation Method 2
detecting, in a case that a low level is outputted, an AC current in the pure induction mode
Data Source
AI summary
An AC/DC leakage detection method, which supports the detection of DC leakage and AC leakage. A DC leakage current and a low-frequency leakage current are measured by means of magnetic modulation technology, an AC signal is measured in the form of pure induction, and two detection modes are performed in a time-sharing manner. A collected leakage signal is converted into a digital signal through an AD converter. By means of the method of the present invention, the processing of a leakage signal is divided into three channels for respectively processing DC leakage, low-frequency AC leakage, and high-frequency AC leakage. The overall effective value of residual current is calculated by integrating results of DC detection and AC detection. The method of the present invention supports the detection of a suddenly increased current; and when there is a suddenly increased current, detection mode switching is performed by detecting the current sudden change of the current.