Leakage Current Detection Device With Calibration Winding
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Solution Overview
Problem
Non-isolated photovoltaic inverters generate leakage currents, causing grid current distortion and electromagnetic interference, and existing leakage current transducers are expensive, unable to detect currents above 500 mA or frequencies higher than 3.5 kHz, and lack calibration capabilities, affecting detection accuracy.
Innovation Solution
A detection device with a magnetic core, detection and calibration windings, and circuits that form self-oscillation to generate excitation signals, allowing for accurate leakage current detection and calibration, using a drive circuit, sampling resistor, differential sampler, and low-pass filter to improve detection accuracy and bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If an integrated leakage current transducer is used, then the detection device can be compact, but it cannot detect leakage currents with amplitude greater than 500 mA or frequency higher than 3.5 kHz
Solution Approach 1:
The patent divides the detection system into separate functional modules: a magnetic core for magnetic field concentration, a detection winding for signal generation, a drive circuit for excitation, and a detection circuit for signal processing. This segmentation allows each component to be optimized independently, achieving both compact size and high detection capability for currents >500mA and frequencies >3.5kHz.
Solution Approach 2:
The patent implements a nested structure where the detection winding and calibration winding are wound around the magnetic core, and the magnetic core is integrated within the circuit board assembly. This nesting achieves space efficiency while maintaining the detection performance required for high current and frequency applications.
2Device complexity
If an integrated leakage current transducer is used, then the device structure is simplified, but it cannot perform leakage current calibration
Solution Approach 1:
The magnetic core serves multiple functions: it concentrates magnetic fields for detection, enables calibration through the calibration winding, and provides structural integration. The calibration winding shares the same magnetic core as the detection winding, allowing the system to perform both detection and calibration functions without increasing overall structural complexity.
Solution Approach 2:
The calibration winding acts as an intermediary that introduces known calibration currents into the magnetic core, enabling the detection circuit to be calibrated against standard values. This intermediary mechanism allows calibration capability to be added without fundamentally changing the transducer structure.
3Device complexity
If conventional detection circuits are used, then the circuit design is simple, but the detection accuracy for high-frequency leakage currents is insufficient
Solution Approach 1:
The drive circuit generates dynamic excitation signals that periodically magnetize and demagnetize the magnetic core at frequencies exceeding 3.5 kHz. This dynamic operation enables the detection circuit to accurately track high-frequency leakage currents while maintaining a relatively simple circuit architecture through self-oscillation mechanisms.
Solution Approach 2:
The detection circuit incorporates feedback mechanisms where the detected signal is processed and used to control the drive circuit, forming a closed-loop system. This feedback enables high-frequency detection accuracy by continuously adjusting the excitation based on the detected leakage current, without requiring overly complex circuit design.
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
The solution enables accurate detection of high-frequency leakage currents beyond 3.5 kHz and 500 mA, reduces manufacturing costs, and minimizes human error, improving the accuracy and reliability of leakage current measurement while being less sensitive to temperature changes.
Implementation Method 1
a magnetic core, a detection winding and a calibration winding both wound on the magnetic core
Data Source
AI summary
A detection device, an inverter, and a detection method are disclosed. The detection device is configured to detect a leakage current flowing through a conductor. The detection device includes a magnetic core, a detection winding and a calibration winding both wound on the magnetic core, a detection circuit, and a calibration circuit. The detection circuit is coupled to the detection winding, and configured to sample a detection signal of the detection winding to obtain a leakage current detection value. The calibration circuit is coupled to the calibration winding, and configured to provide a calibration signal to the calibration winding.