Low-Voltage Isolation Fault Detection on EV Propulsion Bus Rails
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Solution Overview
Problem
Conventional isolation resistance monitoring systems in high-voltage systems of electric or hybrid-electric vehicles are inefficient in rapid testing and complexity, posing safety risks during fault detection.
Innovation Solution
A method and high-voltage circuit that uses high-voltage contactors and capacitors in series across bus rails, with an isolated DC/DC converter to convert high-voltage to low-voltage for capacitors, allowing for simultaneous charging and fault detection without hazardous electrical currents, enabling rapid and safe isolation resistance testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional isolation resistance monitoring systems are used, then safety monitoring is provided, but testing speed is slow and system complexity is high
Solution Approach 1:
The patent changes the voltage parameter from high voltage to low voltage (below 60V) for the test signal, enabling faster testing without hazardous currents. This parameter change resolves the contradiction by allowing rapid isolation resistance testing while maintaining safety and reducing system complexity.
Solution Approach 2:
The patent introduces a low-voltage test signal as an intermediary between the high-voltage system and the measurement device. This intermediary enables fast testing without requiring complex high-voltage measurement circuits, thus improving testing speed while reducing device complexity.
2Reliability
If high-voltage testing is performed for isolation fault detection, then accurate fault detection is achieved, but safety risks increase due to hazardous electrical currents
Solution Approach 1:
The patent changes the voltage parameter from high voltage to low voltage (below 60V) for testing, eliminating hazardous currents while maintaining the ability to detect isolation faults. This resolves the contradiction by ensuring safety without sacrificing fault detection accuracy.
Solution Approach 2:
The patent converts the potentially harmful high-voltage test signal into a safe low-voltage test signal, transforming a hazardous testing method into a safe one. This allows accurate fault detection while eliminating safety risks from hazardous currents.
3Productivity
If rapid isolation resistance testing is implemented, then testing speed improves, but system complexity increases
Solution Approach 1:
The patent uses low-voltage testing to achieve rapid isolation resistance measurement without requiring complex high-voltage switching and measurement circuits. This parameter change enables high testing efficiency while keeping the monitoring system simple.
Solution Approach 2:
The patent introduces a low-voltage test signal as an intermediary that simplifies the measurement process, enabling rapid testing without complex high-voltage circuitry. This intermediary approach improves productivity while reducing system complexity.
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 allows for quick and safe detection of isolation faults, reducing complexity and improving safety by performing tests below 60 Volts, enabling rapid vehicle startup and cost-efficient fault classification.
Implementation Method 1
operating an isolated DC/DC converter for converting a supplied high-voltage from a high-voltage battery of the high-voltage battery side to a low-voltage output on the high-voltage propulsion side
Implementation Method 2
a first and second capacitors connected in series across the positive and negative high-voltage bus rails, and a common junction of the first and second capacitors is connected to the chassis
Data Source
AI summary
A method for detecting an isolation fault in an isolation resistance between a positive and negative high-voltage bus rail and a vehicle chassis on a high-voltage propulsion side of a high-voltage system of an electric or hybrid-electric vehicle. The high-voltage system is split into a battery side and propulsion side by means of two high-voltage contactors located in the positive and negative high-voltage bus rails. The propulsion side includes first and second capacitors connected in series across the positive and negative bus rails, a common junction of the first and second capacitors connected to the chassis. The method supplies a low-voltage output to the positive and negative bus rails to charge the capacitors; and determines, based on charging current, voltage level or energy level of the capacitors, whether an isolation fault is present between the positive and/or negative high-voltage bus rail and the vehicle chassis on the propulsion side.