Main Contactor Weld Detection Using Inrush Voltage Thresholds
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Solution Overview
Problem
In electrified vehicles, contactor welding can occur due to high inrush currents, leading to potential electrical arcs and terminal melting, which existing systems fail to effectively detect and prevent.
Innovation Solution
A system and method involving a controller that monitors inrush currents through the main contactor, commanding it to sequentially open and close based on sensed voltage thresholds to prevent welding, utilizing a precharge circuit to reduce voltage differences and a current sensor to detect excessive currents, thereby preventing contactor welds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the main contactor is commanded to open and close during normal operation, then the vehicle can be driven, but contactor welding may occur due to high inrush currents causing electrical arcs and terminal melting
Solution Approach 1:
The system performs a preliminary weld detection test by commanding the main contactor to open and close before allowing normal vehicle operation. This preliminary action detects potential welding issues before they occur during actual driving, preventing contactor failure while enabling vehicle drivability.
Solution Approach 2:
The controller monitors inrush current through the main contactor and provides feedback to determine if welding has occurred. Based on this feedback, the controller commands the contactor to open and close in a controlled manner, adjusting operation to prevent welding while maintaining vehicle drivability.
2Reliability
If the controller commands the main contactor to sequentially open and close for weld detection, then contactor welding is prevented, but vehicle operation is inhibited until the test is complete
Solution Approach 1:
The weld detection test is performed as a preliminary action before normal vehicle operation. By completing the contactor open-close sequence beforehand, the system ensures contactor reliability is verified while minimizing impact on vehicle operation availability.
Solution Approach 2:
The controller dynamically adjusts vehicle operation based on the weld detection test results. If the contactor successfully completes the open-close sequence without welding, vehicle operation is permitted. This dynamic response balances weld prevention with maintaining vehicle availability.
3Measurement precision
If the controller monitors inrush current voltage to detect welding, then accurate weld detection is achieved, but complex voltage threshold monitoring is required
Solution Approach 1:
The controller monitors voltage parameters (comparing first and second voltage thresholds) during contactor operation to detect welding. By changing and comparing voltage parameters rather than using complex physical sensors, the system achieves accurate weld detection while minimizing added device complexity.
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
Effectively prevents contactor welding by accurately detecting high inrush currents and controlling the main contactor to avoid electrical arcs and terminal damage, ensuring safe and reliable vehicle operation.
Implementation Method 1
A vehicle includes a traction battery, an electric machine, a main contactor electrically connected between the traction battery and the electric machine, and a controller. The controller, responsive to data indicating a voltage associated with an inrush current through the main contactor exceeds a first threshold, commands the main contactor to open and inhibit the vehicle from being driven.
Implementation Method 2
utilizing a precharge circuit to reduce voltage differences and a current sensor to detect excessive currents, thereby preventing contactor welds
Data Source
AI summary
A vehicle includes a controller that, responsive to data indicating a voltage associated with an inrush current through a main contactor exceeds a first threshold, commands the main contactor to open and inhibits the vehicle from being driven, and responsive to data indicating the voltage exceeds a second threshold less than the first threshold, commands the main contactor to sequentially open and then close.