EV Battery Contactor Weld Checking Using Differential Impedance Sensing
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Solution Overview
Problem
Existing systems for detecting contact welding in high-current applications, such as electric vehicles, lack sensitivity and reliability, leading to potential safety issues and maintenance challenges due to permanent electrical connections.
Innovation Solution
A system utilizing a differential amplifier with balanced impedance networks and a control unit to detect contactor state based on signal differences, providing improved sensitivity and reliability through noise immunity and accurate determination of contactor welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If visual inspection and electrical measurements are used to detect contact welding, then the detection method is simple, but the sensitivity and reliability are insufficient
Solution Approach 1:
The patent replaces manual visual inspection and basic electrical measurements with an automated differential measurement system using a differential amplifier. This substitutes mechanical/manual detection methods with an electronic system that provides both simplicity in operation and high reliability through differential signal processing that rejects common-mode noise and enhances sensitivity to welding-induced impedance changes.
2Measurement precision
If thermal imaging and functional testing are used to detect contact welding, then the detection capability is improved, but the system complexity increases
Solution Approach 1:
The patent extracts and isolates the critical detection function by using a dedicated differential amplifier circuit that focuses solely on measuring impedance changes across the contactor. This separates the weld detection function from complex thermal imaging and functional testing systems, achieving high measurement precision through a relatively simple and targeted electrical measurement approach.
3Reliability
If a differential amplifier with balanced impedance networks is used, then the sensitivity and noise immunity are improved, but the circuit complexity increases
Solution Approach 1:
The patent employs a symmetric/differential circuit architecture where two balanced impedance networks are configured to create symmetry in the normal state. When welding occurs, the symmetry is broken, creating an asymmetric differential signal that the amplifier detects. This use of symmetry and its deliberate breaking provides high sensitivity and noise immunity while maintaining reasonable circuit complexity through standardized differential amplifier design.
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 system offers faster, more accurate, and robust detection of contactor welding, reducing false positives and enabling safer maintenance by identifying welding issues in electric vehicle systems.
Implementation Method 1
a differential amplifier electrically connected to the first impendence network and the second impedance network, the differential amplifier being configured to receive a first signal via the first impedance network and a second signal via the second impedance network and to provide a difference signal based on the first and second signals
Data Source
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AI summary
A system for weld checking a contactor for a traction battery of an electric vehicle is disclosed. The contactor is arranged to be in a closed or an open state to electrically connect or disconnect the traction battery from an electrical load. The system comprising: an electric circuit; the electric circuit comprises a first impedance network having a first impedance, and a second impedance network having a second impedance equal to the first impedance; and a differential amplifier electrically connected to the first and second impedance networks, the differential amplifier being configured to receive a first signal via the first impedance network and a second signal via the second impedance network and to provide a difference signal based on the first and second signals. The system is configured to determine whether the contactor is in the closed state or in the open state based on the difference signal.