High-Voltage Bus Impedance Measurement for Welded Contactor Detection
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Solution Overview
Problem
Existing methods for detecting fault conditions in high-voltage vehicles, such as welded contactors, are inadequate, particularly in isolating faults and detecting single welded contactors on the negative rail, and require communication-intensive processes that are not optimal for all scenarios.
Innovation Solution
A method involving impedance measurement between the high-voltage bus and the vehicle chassis, comparing closed and open states of contactors, and using a look-up table to determine fault conditions based on impedance levels, with a threshold ratio to set error codes for maintenance responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage drop measurement method is used to detect welded contactors, then detection capability is improved, but system complexity and communication requirements increase
Solution Approach 1:
The patent extracts the fault detection function from complex communication-intensive diagnostic systems and implements it through simple impedance measurement circuitry integrated into the ESS controller. This allows welded contactor detection without requiring other control modules to be active or communicate, thereby reducing system complexity while maintaining detection precision.
Solution Approach 2:
The ESS controller performs self-diagnosis by measuring impedance values internally without requiring external diagnostic equipment or communication with other control modules. The controller autonomously determines fault conditions based on measured impedance values, enabling the system to service itself and reducing overall system complexity.
2Loss of information
If communication-intensive messaging processes are used to detect fault conditions, then diagnostic information is obtained, but response time and system efficiency deteriorate
Solution Approach 1:
The patent implements preliminary fault detection by continuously monitoring impedance values during normal operation and immediately upon contactor opening. The controller is pre-programmed with threshold values and detection algorithms, allowing instant fault identification without requiring post-fault communication cycles or diagnostic sequences, thereby eliminating diagnostic response time delays.
3Measurement precision
If traditional voltage drop diagnostics are used, then welded contactor detection is possible, but single welded contactors on negative rail cannot be detected
Solution Approach 1:
The patent transitions from single-point voltage drop measurement to multi-point impedance measurement across different circuit configurations. By measuring impedance with contactors in both closed and open states, and comparing values across positive and negative rails, the system detects single welded contactors that traditional methods miss, thereby expanding fault condition coverage while maintaining measurement precision.
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 detects high-voltage fault conditions, including welded contactors and disconnected components, enabling timely maintenance responses and improving the reliability of high-voltage system operation.
Implementation Method 1
measuring an electrical impedance value between the high-voltage bus and the vehicle chassis
Data Source
AI summary
A method includes detecting high-voltage faults, such as welded contactors or disconnected components, in a vehicle by measuring the total electrical impedance between positive and negative rails of a high-voltage bus and a ground or chassis, comparing the impedance before and after opening the contactors, and executing a maintenance response. The response includes setting an error code when the open impedance level is less than a threshold multiple of the closed impedance level. A vehicle includes a chassis, energy storage system (ESS), motor/generator, and a high-voltage bus conducting electrical current from the ESS to the motor/generator. Contactors are positioned along each of the rails of the bus, a device for measuring a total electrical impedance level between the chassis and each of the rails, and a controller for determining a welded contactor condition of at least one of the contactors based on the measured total electrical impedance level.