Contactor Weld Detection Using Open-Circuit Voltage Measurement

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Solution Overview

Problem

Contactors in electrical energy storage systems can weld together due to high power arcs or excessive currents, leading to operational delays and wear, necessitating a fast and reliable method to detect welding without active control or closing/opening the contactors.

Innovation Solution

A computer system using processing circuitry to measure voltages across open contactors and evaluate these measurements against a voltage criterion to determine welding, without requiring the contactors to be closed or opened, thereby reducing wear and downtime.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional weld testing methods are used requiring closing and opening of contactors, then welding detection can be performed, but contactor wear increases and operational downtime increases

Engineering Contradiction:

Improvewelding detection accuracyVSAvoidcontactor lifetime

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent replaces mechanical contactor operation (closing and opening) with an electrical measurement system. By measuring voltages at terminals during normal operation and calculating contactor voltages through circuit analysis, the system detects welding without mechanical actuation, thereby eliminating wear from repeated contactor operation while maintaining reliable welding detection capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces voltage measurements as an intermediary to detect welding indirectly. Instead of directly testing contactor closure through mechanical operation, the system measures voltages at accessible terminals and uses circuit analysis to infer contactor voltage and detect welding, serving as a non-intrusive intermediary detection method

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If traditional weld testing methods requiring contactor closure are used, then welding can be detected, but equipment downtime increases

Engineering Contradiction:

Improvewelding detection capabilityVSAvoidequipment downtime

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent performs welding detection continuously during normal operation rather than requiring separate testing procedures. By measuring voltages during regular system operation and continuously evaluating contactor voltage, the system detects welding in real-time without interrupting equipment operation, eliminating the need for scheduled downtime for weld testing

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent enables continuous welding detection during normal system operation. The voltage measurement and evaluation process runs continuously alongside normal equipment operation, maintaining uninterrupted monitoring of contactor health without requiring the equipment to be taken offline for testing, thus preserving continuous useful action

Inventive Principle:

Principle #20Continuity of useful action

3Reliability

If repeated contactor closing and opening is performed for weld testing, then welding detection is achieved, but contactor wear increases

Engineering Contradiction:

Improveweld testing accuracyVSAvoidcontactor wear

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent enables the system to self-diagnose welding conditions during normal operation without requiring external testing procedures. The continuous voltage measurement and evaluation system allows the equipment to monitor its own contactor health in real-time, eliminating the need for external personnel to perform repeated contactor operations for testing purposes

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS20250277876A1System and method for weld check of contactors

Publication Date: 2025.09.04 VOLVO TRUCK CORP

AI summary

A computer system has processing circuitry to request opening of a positive contactor and a negative contactor, acquire measurements of a first voltage, a second voltage, a third voltage, and a fourth voltage between a positive pole and a negative pole, and ground, calculate a first contactor voltage across one of the negative contactor and the positive contactor and a second contactor voltage across the other one of the negative contactor and the positive contactor, determine that one or more of the positive contactor and the negative contactor is welded when the respective one of the first contactor voltage and the second contactor voltage fulfill the voltage criterion.