Transformer-Based Ground Fault Detection for High-Voltage Systems
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Solution Overview
Problem
Existing vehicle ground fault detection circuits using coupling capacitors are vulnerable to breakdown from temporary AC noise, especially as the areas of use expand, making it difficult to predict noise sources and ensuring sufficient AC withstand voltage.
Innovation Solution
A vehicle ground fault detection apparatus utilizing a transformer to block DC components and an oscillation circuit to measure peak voltage in the high-voltage system, which compares the peak voltage with predetermined values to detect ground faults without increasing the number of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coupling capacitor is used to detect ground fault, then the detection function is enabled, but the insulation is vulnerable to breakdown from AC noise
Solution Approach 1:
The patent introduces a coupling transformer as an intermediary component between the high-voltage system and low-voltage system. The transformer blocks DC components while allowing AC signals to pass through for ground fault detection, replacing the vulnerable coupling capacitor. This intermediary device provides galvanic isolation and protects against AC noise breakdown while maintaining detection functionality.
Solution Approach 2:
The patent changes the coupling method from capacitive coupling to transformer coupling. By changing the coupling parameter from capacitor impedance to transformer inductance ratio, the system achieves both AC signal transmission and DC blocking with enhanced noise immunity. The transformer's magnetic coupling provides inherent protection against AC noise while maintaining the detection function.
2Strength
If the withstand voltage is increased to handle unpredictable noise sources, then the AC withstand voltage may become insufficient with the coupling capacitor
Solution Approach 1:
The coupling transformer serves as a robust intermediary that provides high AC withstand voltage capability through its magnetic isolation mechanism. The transformer structure inherently handles voltage stress better than capacitors, providing enhanced protection against unpredictable noise sources without requiring additional protective components.
Solution Approach 2:
The patent employs a composite coupling approach using transformer windings with different insulation layers and magnetic materials. This composite structure provides both high voltage withstand capability and AC signal transmission, resolving the contradiction between strength and complexity by integrating multiple functions into a single component.
3Adaptability or versatility
If the areas of vehicle use expand, then more unpredictable noise sources may be connected, but the coupling capacitor cannot predict or prepare for these noise types
Solution Approach 1:
The coupling transformer provides universal protection against various noise sources through its magnetic isolation mechanism. Unlike capacitors that are sensitive to voltage stress and noise type, the transformer adapts to different noise conditions while maintaining reliable isolation, enabling the system to expand to new application areas with unpredictable noise environments.
Solution Approach 2:
The transformer-based coupling circuit provides universal functionality for ground fault detection across different vehicle applications and noise environments. The same coupling structure handles various AC noise types and voltage conditions, making the system adaptable to expanding application areas without compromising reliability.
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 provides enhanced insulation resistance against temporary AC noise, allowing for reliable detection of ground faults without component increase, and simplifies the measurement of AC voltage, thereby preventing circuit breakdown.
Implementation Method 1
a transformer configured to block a DC component between the low-voltage system and the high-voltage system
Implementation Method 2
an oscillation circuit provided in the low-voltage system and connected to a primary coil of the transformer
Data Source
AI summary
A vehicle ground fault detection apparatus (1) detects a ground fault of a high-voltage system electrically insulated from a vehicle body connected to a low-voltage system and includes a transformer (2) blocking a DC component between the low- and high-voltage systems, an oscillation circuit (3), in the low-voltage system, connected to a primary coil (21) of the transformer (2), and a voltage dividing resistor (4), in the high-voltage system, connected to a secondary coil (22) of the transformer (2). The vehicle ground fault detection apparatus (1) measures a positive peak of voltage generated in the voltage dividing resistor (4) by voltage induced in the secondary coil (22) through AC voltage generated by the oscillation circuit (3) and detects the ground fault using the peak voltage. The insulation of the coupling portion between the ground fault detection circuit and the high-voltage system circuit does not suffer breakdown during temporary AC noise.