Insulation Fault Detection Circuit for Electric Vehicle Battery Systems
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Solution Overview
Problem
Current insulation fault detection systems in electric vehicles are inadequate, particularly in detecting faults at intermediate points of the battery and locating fault positions, due to limitations in resistive and capacitive measurement methods, which can lead to safety issues and increased costs.
Innovation Solution
A circuit that applies controlled voltage between a battery terminal and the vehicle's chassis to induce a current through an insulation resistance, allowing for accurate measurement and localization of insulation faults using a controllable voltage generator and resistors, enabling detection of faults at any point in the battery without requiring connection to both terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistive measurement circuits are used to detect insulation faults, then the circuit can measure leakage current, but it requires connection to both battery terminals which complicates integration and cannot detect faults at intermediate points
Solution Approach 1:
The patent extracts the essential measurement function by connecting the voltage divider bridge to only one battery terminal (negative terminal) instead of both terminals. This extraction simplifies the circuit integration while maintaining the ability to detect insulation faults, including those at intermediate points of the battery assembly.
Solution Approach 2:
The detection circuit is designed to perform multiple functions: detecting insulation faults at any point along the battery, locating the position of faults, and measuring leakage current. This multi-functionality is achieved through the voltage divider bridge configuration that can sense voltage variations corresponding to different fault locations.
2Measurement precision
If capacitive discharge measurement circuits are used, then insulation faults can be detected, but the capacitance value drifts over time falsifying calculations and large capacitors are required for safety
Solution Approach 1:
The patent replaces large, expensive safety capacitors with a resistive measurement approach using a voltage divider bridge. This substitution uses smaller, more stable resistive components that do not suffer from capacitance drift over time, thereby improving measurement reliability while reducing component size and cost.
Solution Approach 2:
The patent changes the measurement parameter from capacitive discharge time constant to voltage division ratio. By measuring voltage across the voltage divider bridge components, the system achieves stable, drift-free measurements that are not subject to the time-dependent degradation inherent in capacitive measurement methods.
3Object-affected harmful factors
If insulation monitoring is implemented to ensure safety, then user protection is improved, but the system complexity and cost increase
Solution Approach 1:
The patent combines the insulation monitoring function with the existing battery management system by integrating the voltage divider bridge detection circuit into the battery's electrical architecture. This merging allows safety monitoring to be achieved without adding a separate, complex monitoring system, thereby reducing overall system complexity and cost.
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 facilitates reliable and precise detection of insulation faults, improving safety by identifying fault positions within the battery assembly and reducing the complexity and cost of integration, while maintaining user safety by preventing dangerous leakage currents.
Implementation Method 1
A circuit which applies a controlled voltage between a terminal of the battery and the chassis in order to induce a current through an insulation resistance
Data Source
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AI summary
The invention relates to an electrical system comprising: - terminals (V+, V-) capable of being connected to an installed electrical power source (4) capable of delivering an electrical voltage between said terminals; - a circuit for detecting an electrical insulation fault between the electrical power source and a housing (14) forming a floating electrical ground. The detection circuit comprises: • a controllable voltage generator (40) capable of polarising the housing and the single first terminal at different potentials; • a current measurement device (44) measuring current entering on said first terminal and leaving at a point of the source; • a control unit (46) capable of calculating a value of at least one insulation resistance from said at least one measured current value.