Contactor Failure Detection via Voltage Drop Analysis
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Solution Overview
Problem
Existing methods for determining contactor failures in battery packs of electric vehicles are inefficient, leading to prolonged activation and deactivation times, which inconvenience drivers and hinder quick power input/output during vehicle use.
Innovation Solution
A contactor failure determining method that involves outputting control signals to switch contactors and determining failure states based on voltage drops or rises in the load, using predetermined values to assess the presence of fixing or melting in contactors, allowing for rapid identification of failures without requiring unnecessary contactor operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contactor failure determination is performed by opening and closing contactors during activation and deactivation of electric vehicle, then failure detection capability is improved, but activation and deactivation time increases causing driver inconvenience
Solution Approach 1:
The patent applies preliminary action by determining contactor failure at the end of power supply before the vehicle fully deactivates. The control device outputs a control signal to open the positive-side contactor, then immediately determines failure based on voltage drop characteristics before proceeding with full deactivation. This allows failure detection to be embedded within the existing power supply cutoff process rather than requiring separate contactor operations.
Solution Approach 2:
The system uses the voltage drop that naturally occurs when the positive-side contactor opens to determine contactor failure. Instead of requiring additional test signals or separate diagnostic operations, the system self-diagnoses by monitoring the inherent electrical characteristics during the power supply cutoff process. The voltage drop serves both as a normal operational effect and as a diagnostic indicator.
2Stability of the object's composition
If contactor failure determination is performed at activation and deactivation only, then power stability during traveling is maintained, but failure determination speed is reduced
Solution Approach 1:
The patent performs failure determination at the end of power supply as a preliminary action before the vehicle completes deactivation. By embedding the diagnostic check within the existing power cutoff sequence, the system achieves faster failure determination without requiring separate test operations that would extend activation or deactivation time.
3Measurement precision
If additional contactor operations are performed for failure determination, then diagnostic accuracy is improved, but operational complexity and time consumption increase
Solution Approach 1:
The system uses the voltage drop that naturally occurs when the positive-side contactor opens to determine contactor failure. Instead of requiring additional test signals or separate diagnostic operations, the system self-diagnoses by monitoring the inherent electrical characteristics during the power supply cutoff process. The voltage drop serves both as a normal operational effect and as a diagnostic indicator.
Solution Approach 2:
The control device performs multiple functions simultaneously: it opens the positive-side contactor to cut power supply, monitors the resulting voltage drop to determine contactor failure, and uses the same voltage information for both operational control and diagnostic purposes. This multi-functionality eliminates the need for separate diagnostic hardware or additional contactor operations.
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 method enables quick determination of contactor failures, reducing the time required for activation and deactivation, ensuring stable power supply and minimizing driver inconvenience by identifying failures during inevitable operations, thus enhancing the efficiency of electric vehicle power management.
Implementation Method 1
determining a presence of fixing of the precharge contactor based on a degree of voltage drop of a voltage applied to the load after the control signal for switching the positive-side contactor to the open state is output
Data Source
AI summary
A contactor failure determining method in includes outputting a control signal for switching a positive-side contactor provided between a positive electrode of a multi-cell battery and a positive electrode of a load to which the multi-cell battery supplies electric power to an open state from a state in which a control signal for controlling the positive-side contactor and a negative-side contactor provided between a negative electrode of the multi-cell battery and a negative electrode of the load to a closed state and a precharge contactor provided between the multi-cell battery and the load to an open state is output, and as a first fixing determining step, determining a presence of fixing of the precharge contactor based on a degree of voltage drop of a voltage applied to the load after the control signal for switching the positive-side contactor to the open state is output.