Contactor Weld Detection Using Actuation Timing

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Solution Overview

Problem

Current methods for detecting welded contacts in contactors, especially in electric vehicle battery packs, fail to accurately identify partial welds due to insufficient design margins, leading to potential arcing and safety hazards.

Innovation Solution

A method involving sending an activation signal to move a conducting member between positions and measuring the time interval for an electrical circuit to close, with adjustments based on physical characteristics like temperature and current, to determine if the conducting member has fully disengaged, thereby detecting partial or full welds and enhancing safety.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If feedback contact is used to detect welded contacts, then detection capability is provided, but false negative outputs occur when design margins are too small

Engineering Contradiction:

Improveweld detection reliabilityVSAvoidpartial weld detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical feedback contact system with an electrical measurement system. Instead of relying on mechanical coupling between feedback and main contacts, the invention measures electrical parameters (current, voltage, resistance) across the contactor terminals to detect welded conditions, eliminating the false negative problem inherent in mechanical feedback systems with small design margins.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the detection parameter from mechanical position (feedback contact closure) to electrical characteristics (current flow, voltage drop, resistance). By monitoring changes in electrical parameters when the contactor should be open, the system can detect partial welds that mechanical feedback systems miss, improving both reliability and measurement precision.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If design margins are reduced to improve contactor compactness, then device size is reduced, but false negative detection occurs

Engineering Contradiction:

Improvecontactor sizeVSAvoidsafety indication reliability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If feedback contact is used to detect welded contacts, then detection capability is provided, but device complexity increases

Engineering Contradiction:

Improveweld detection capabilityVSAvoidfeedback contact mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the detection function from the mechanical feedback contact mechanism and implements it through separate electrical measurement circuits. This separates the actuation function from the detection function, allowing the use of simple electrical measurements rather than complex mechanical feedback systems, thereby reducing device complexity while maintaining or improving detection capability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention uses the existing electrical terminals and control circuitry of the contactor for dual purposes: both for normal operation and for weld detection. By measuring electrical parameters that are already present during normal operation, the system eliminates the need for separate dedicated detection hardware, reducing overall device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20240210475A1Detection of welded contactors

Publication Date: 2024.06.27 SCANIA INDUSTRIAL BATTERIES AB

AI summary

A method of indicating that a conducting member has not fully disengaged from two electrical contacts. The conducting member is movably mounted on an actuator, the actuator being adapted to move between a deactivated position and an activated position, wherein in the activated position the conducting member is in contact with both the electrical contacts. The method comprises: sending an activation signal to move the actuator to the activated position; detecting that the actuator has caused an electrical circuit to be closed; and if the time interval between the sending step and the detecting step is less than a threshold, generating an output indicating that the conducting member was not fully disengaged before the activation signal was sent.