High Voltage Contactor Fault Detection via Active Discharge
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Solution Overview
Problem
In multi-bus systems of electric and hybrid vehicles, fault detection is challenging due to the risk of contactor welding, which can occur when a contactor connects a bus with residual voltage, leading to incomplete discharge and potential electrical issues.
Innovation Solution
A system with a controller that actively discharges one electrical bus until the voltage magnitudes of both buses are within a predefined range, using a shared positive contactor and respective negative contactors, to prevent contactor welding and ensure complete discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contactor connects a bus with residual voltage, then the contactor may weld due to electrical arcing, but preventing connection requires ensuring complete discharge which increases system complexity
Solution Approach 1:
The system performs preliminary discharge of the electrical bus before closing the contactor by activating discharge resistors to reduce voltage below a threshold level. This preliminary action prevents contactor welding by ensuring the bus is sufficiently discharged before contactor operation, resolving the contradiction between reliability and complexity.
Solution Approach 2:
Discharge resistors are introduced as intermediary components between the electrical bus and ground. These resistors provide a controlled path for discharge current, enabling safe voltage reduction without requiring direct short-circuiting. The intermediary resistors protect the contactor while adding manageable complexity to the system.
2Reliability
If the system waits for complete natural discharge of the bus, then contactor welding is prevented, but the process takes excessive time affecting system productivity
Solution Approach 1:
Instead of waiting for natural discharge, the system performs preliminary active discharge using resistors before contactor operation. This accelerates the discharge process from potentially minutes to seconds, maintaining reliability while dramatically improving productivity and system response time.
Solution Approach 2:
The discharge process is implemented as a periodic controlled action rather than a continuous wait state. The controller activates discharge resistors in controlled intervals to achieve target voltage levels, then deactivates them when discharge is sufficient. This periodic control maintains reliability while minimizing time loss and improving overall system productivity.
3Reliability
If the system uses multiple negative contactors for different buses, then fault isolation is improved, but the risk of welding increases due to multiple contactor operations
Solution Approach 1:
The harmful factor of residual voltage is extracted and removed from the system before contactor operation by routing it through discharge resistors to ground. This extraction of energy prevents the welding condition while maintaining the benefits of multiple contactors for fault isolation, resolving the contradiction between reliability and harmful factors.
Solution Approach 2:
The system applies preliminary anti-action by discharging the bus voltage before the contactor closes. This pre-empts the harmful welding effect by eliminating the voltage differential that would cause arcing. The preliminary discharge action counteracts the potential harm before it can occur, protecting the multiple contactors while maintaining fault isolation capabilities.
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 solution effectively prevents contactor welding and ensures complete discharge of the traction battery, enhancing fault detection and reducing the risk of electrical faults in the multi-bus architecture.
Implementation Method 1
A system with a controller that actively discharges one electrical bus until the voltage magnitudes of both buses are within a predefined range
Data Source
AI summary
A system for a vehicle includes a pair of electrical buses connected to terminals of a traction battery via a shared positive contactor and a pair of negative contactors. The system further includes a controller configured to, responsive to a request to close the contactors and a difference between voltage magnitudes of the buses being greater than a predefined threshold, actively discharge one of the buses to reduce the difference.