EV Contactor State Diagnosis Using Optocoupler Current Detection
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Solution Overview
Problem
Existing contactor systems in electric vehicles fail to accurately determine the state of contactors, particularly when they are welded closed, leading to potential circuit malfunctions due to improper opening and closing during drive cycles.
Innovation Solution
A contactor diagnosis system using optocouplers to detect current flow through contactors, allowing a controller to compare theoretical and actual states, and send signals for corrective actions when discrepancies are detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contactors are used to isolate battery from charger or load in high voltage systems, then galvanic isolation is guaranteed, but the system cannot accurately detect when contactors fail to open (welded closed state)
Solution Approach 1:
The patent introduces an optocoupler as an intermediary device that indirectly detects contactor state by monitoring current flow in parallel with the contactor. The optocoupler converts electrical current information into optical signals that can be safely read by the control unit, allowing accurate detection of contactor state without direct electrical connection to high voltage circuits.
Solution Approach 2:
The patent replaces direct electrical measurement methods with optical detection using optocouplers. Instead of using electrical sensors that would require direct contact with high voltage circuits, the system uses optical coupling to detect current flow, substituting electrical measurement with optical sensing for safer and more reliable operation.
2Measurement precision
If optocouplers are used to detect current flow for contactor state determination, then accurate detection is achieved, but the system requires additional parallel circuit components
Solution Approach 1:
The optocoupler serves multiple functions simultaneously: it detects current flow direction, determines contactor state (open/closed), provides electrical isolation between high voltage and control circuits, and generates signals for the control unit. This multi-functionality reduces the need for separate dedicated components for each function.
Solution Approach 2:
The optocoupler acts as an intermediary that simplifies the overall system architecture by providing a single component that handles detection, isolation, and signal generation, rather than requiring separate sensors, isolation devices, and signal conditioners.
3Adaptability or versatility
If current detection method is used to determine contactor state, then detection works independently of battery or charger voltage levels, but the system requires parallel connection of detection means with contactor
Solution Approach 1:
The optocoupler serves as an intermediary detection device that measures current flow characteristics to infer contactor state, rather than directly measuring voltage. This current-based indirect measurement approach allows the system to determine contactor state regardless of the specific voltage level present in the circuit.
Solution Approach 2:
The system substitutes direct voltage measurement with optical current detection. By using the optocoupler to detect current flow and convert it to optical signals, the system can determine contactor state independently of voltage levels, as current flow patterns remain consistent indicators of contactor position across different voltage conditions.
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
Accurately determines contactor states, preventing circuit malfunctions by ensuring proper opening and closing, and operates independently of battery or charger voltage levels.
Implementation Method 1
The means for detecting a current passing through the means is an optocoupler
Data Source
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AI summary
System for diagnosing the state of a contactor of an electric vehicle comprising: - a contactor (1, 2), - means (3) for detecting a current passing through the means (3), located in parallel to the contactor (1, 2), and - a controller (14) operatively connected to the contactor (1, 2) and to the means (3) for detecting a current passing through it, the controller (14) being configured for: ∘ communicating with the contactor (1, 2) and registering a theoric state of the contactor (1, 2), ∘ receiving a signal from the means (3): ▪ if current is passing through the means (3), the received signal is open, and ▪ if current is not passing through the means (3), the received signal is closed, ∘ comparing the theoric state of the contactor with the state of the contactor received from the means (3) for detecting a current passing through it.