DC Line Current Diagnosis Using Impedance Sub-Circuits
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Solution Overview
Problem
Current systems require multiple devices to diagnose the condition of multiple contacts in switching devices, especially in high-voltage circuits, which is inefficient and may not be suitable for applications like electric and hybrid vehicles where safety and reliability are critical.
Innovation Solution
A system that uses a single circuit detector with a current generator to deliver alternating current through two sections of a direct current line, employing sub-circuits with different impedances to assess the status of each section by measuring impedance changes, allowing for the diagnosis of multiple contacts without direct current circulation between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple devices are used to diagnose multiple contacts in switching devices, then diagnostic coverage is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple diagnostic functions into a single diagnostic device that can diagnose multiple contacts simultaneously. The device includes a current generator and detection circuitry that can sequentially or concurrently test multiple contacts through shared measurement paths, eliminating the need for separate diagnostic devices for each contact.
Solution Approach 2:
The diagnostic device is designed with universal functionality to diagnose different types of contacts and circuit configurations. It includes programmable control logic and configurable measurement parameters that allow the same device to adapt to various diagnostic scenarios, replacing multiple specialized devices.
2Measurement precision
If potential measurement with divider resistors is used in high-voltage circuits, then measurement capability is improved, but circuit complexity and safety requirements increase
Solution Approach 1:
The patent replaces traditional potential measurement methods using divider resistors with an alternative approach that uses current injection and voltage drop measurement. Instead of directly measuring high voltage through resistive dividers, the system injects a known current and measures the resulting voltage characteristics, simplifying the measurement circuit while maintaining accuracy.
Solution Approach 2:
The diagnostic system changes the measurement parameter from direct potential measurement to current-based measurement. By injecting a diagnostic current and measuring the voltage response or impedance characteristics, the system avoids the complexity of high-voltage divider circuits while achieving accurate diagnostic information.
3Reliability
If isolation circuits and DC/DC converters are used to separate high voltage potential, then safety is improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary diagnostic current that serves as a mediator between the high-voltage circuit and the low-voltage diagnostic electronics. This diagnostic current allows the system to obtain measurement information from high-voltage contacts without requiring direct electrical connection or complex isolation barriers, as the measurements are taken through the current path itself.
4Loss of energy
If disconnect switches are used to avoid permanent current draw in measuring resistor chains, then energy efficiency is improved, but circuit complexity increases
Solution Approach 1:
The diagnostic system uses periodic current injection instead of continuous current draw. The current generator activates only during diagnostic measurement intervals, injecting test currents periodically to assess contact conditions. This periodic operation eliminates the need for disconnect switches while achieving energy efficiency, as the measurement circuit draws current only when needed for diagnosis.
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
Enables efficient diagnosis of multiple contacts in a switching device with a single detector, improving safety and reliability by preventing direct current circulation and isolating high voltage potentials, thus reducing the complexity and cost of diagnostic systems.
Implementation Method 1
a current generator adapted to deliver an alternating current (AC) to said sections to be diagnosed
Implementation Method 2
the first sub-circuit and the second sub-circuit having an impedance. The impedance of each of the sub-circuits being of different value seen from the device for diagnosing the presence of an electric current
Data Source
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AI summary
System for diagnosing the presence of an electric current flowing through at least two sections of two direct current (DC) lines (20, 21), the system comprising a device (4) for diagnosing the presence of an electric current flowing through a section of a direct current (DC) line comprising: - a current generator (5) adapted to deliver an alternating current (AC) to said section to be diagnosed, - a first and a second electrical terminals (A, B), and - a computing module, The system further comprises an electric circuit comprising a first (10) and a second sub-circuit (11) having an impedance, the impedance of each of the subcircuits (10, 11) being of different value seen from the device (4) for diagnosing the presence of an electric current, and the computing or electronic module being adapted to assess the impedance of the alternating current (AC) delivered to the first and second sections.