DC Charging Contactor Fault Detection Using Internal Reference Voltage
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Solution Overview
Problem
Existing diagnostic methods for DC charging contactors in electric vehicles often fail to reliably distinguish between fault and no fault states due to disruptive influences from load conditions, vehicle architecture, and the need for precharging, which can lead to uncontrolled voltage application and potential destruction of the contactors.
Innovation Solution
A method involving applying a charging voltage with positive and negative poles between two contactors, driving them into different states, and measuring voltage potentials to identify malfunctions using an internal reference DC voltage, allowing for safe and efficient diagnosis without additional wiring or expensive auxiliary contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If voltage measurement is performed to detect contactor switching state, then diagnostic capability is improved, but measurement reliability deteriorates due to load conditions, vehicle architecture constraints, and precharging requirements
Solution Approach 1:
The patent introduces auxiliary contacts as intermediary elements that provide a dedicated signal path for monitoring contactor switching state. These auxiliary contacts are mechanically linked to the main contactors and provide a reliable indication of the actual switching state independent of the complex voltage measurements affected by load conditions and vehicle architecture.
Solution Approach 2:
The patent replaces the electrical measurement system (voltage measurement affected by electrical load conditions) with a mechanical indication system (auxiliary contacts that physically reflect the contactor position). This mechanical-to-electrical signal conversion provides more reliable fault detection by eliminating the influence of electrical load variations.
2Reliability
If additional auxiliary contacts are added to contactors for monitoring, then diagnostic reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the monitoring function with the existing contactor structure by integrating auxiliary contacts into the same mechanical assembly. The auxiliary contacts share the same actuation mechanism and mounting structure as the main contactors, thereby providing additional diagnostic capability without requiring separate actuators or complex additional mechanisms.
Solution Approach 2:
The auxiliary contacts serve multiple functions: they provide fault detection capability, indicate switching state, and can be used for diagnostic signaling. This multi-functionality allows a single additional component to address multiple diagnostic needs, reducing the overall complexity compared to implementing separate monitoring systems for each function.
3Strength
If precharging is performed before switching to avoid contactor destruction, then contactor protection is improved, but charging time increases
Solution Approach 1:
The patent performs preliminary diagnostic actions (voltage measurement and auxiliary contact monitoring) before the main switching operation to identify potential faults. By detecting stuck contactors in advance through the auxiliary contacts, the system can prevent unnecessary precharging delays while still protecting against contactor destruction by identifying faults that would prevent proper switching.
Solution Approach 2:
The auxiliary contacts provide real-time feedback on the actual switching state of the contactors. This feedback mechanism allows the control system to verify successful switching and adjust the precharging timing accordingly, reducing unnecessary delays while maintaining contactor protection by detecting faults that would prevent proper operation.
Data Source
AI summary
Various embodiments include methods for identifying a malfunction of a DC voltage charging connection in an electric vehicle. An example includes: driving two contactors into an open or closed state without applying a charging voltage; applying an internal reference DC voltage of the electric vehicle between both contactors, including applying a positive pole of the reference DC voltage at the first contactor and a negative pole at the second; measuring a first voltage potential between the contactors on a respective output side; measuring a second voltage potential between the contactors on a respective input side of the contactors; and identifying a malfunction of the two contactors based at least in part on the first voltage potential and the second voltage potential.