Automobile Battery Charger Leakage Current Detection
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Solution Overview
Problem
Circuit breakers can become 'blinded' under certain conditions, failing to detect leakage currents at 50Hz frequencies, which poses a risk of electric shock to individuals, especially in motor vehicle battery charging systems where leakage currents can be dangerous due to insulation defects and high DC or high-frequency AC components.
Innovation Solution
A method and system for controlling a motor vehicle battery charger that measures the variation of leakage current amplitude over time, determines components at different frequencies, and compares these to threshold values to prevent blinding by interrupting power supply if any component exceeds its threshold, using signal processing techniques like filtering, amplification, rectification, and clipping to identify and address potential blinding and leakage issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If intense charging currents are used to charge the vehicle battery quickly, then charging speed is improved, but leakage currents with high DC and high-frequency AC components are generated that can blind circuit breakers
Solution Approach 1:
The system performs preliminary analysis of the leakage current spectrum before dangerous blinding conditions can develop. By continuously monitoring the spectral composition during charging, the system detects the emergence of high DC or high-frequency AC components early and triggers protective disconnection before the circuit breaker becomes blinded and fails to protect. This preliminary detection prevents the harmful condition from manifesting.
Solution Approach 2:
The patent converts the harmful blinding effect into a detectable signature. The high DC and high-frequency AC components that would normally blind the circuit breaker are instead used as diagnostic indicators. The detection system identifies these components as signatures of blinding conditions and uses them to trigger alternative protective measures, turning the harmful phenomenon into a useful detection signal.
2Measurement precision
If leakage current measurement is performed continuously to detect blinding conditions, then detection accuracy is improved, but system complexity and computational requirements increase
Solution Approach 1:
The patent segments the leakage current analysis into distinct frequency components: DC component, low-frequency AC component (including 50Hz), and high-frequency AC component. Each segment is analyzed independently using appropriate detection methods. This segmentation allows the system to focus computational resources on detecting specific blinding indicators without processing the entire spectrum uniformly, reducing overall complexity while maintaining precision.
Data Source
Figure 1~2
AI summary
Automobile vehicle battery charger, furnished with a leakage current sensor and able to be linked to an electrical supply network by way of a circuit breaker, comprising a means for determining (13) components of the leakage currents at different frequencies, a means (14) of comparing the components of the leakage currents with stored thresholds, and a means (15) of cutting off the electrical supply to the charger as a function of the comparison of the components of the leakage currents with the stored thresholds.