Charger Contactor Double Weld Detection

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Solution Overview

Problem

Electrified vehicles face issues with contactors becoming welded closed due to high voltage stress, leading to improper operation and failure to isolate high-voltage components, which can result in safety hazards and operational failures.

Innovation Solution

A controller is programmed to manage charger contactors and a precharge contactor to detect and prevent double-welded contactor conditions by monitoring voltage changes across terminals and the high-voltage bus, commanding contactors to open or close based on predetermined voltage thresholds, and outputting diagnostic codes for faulty conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If charger contactors are used to selectively electrically couple charger terminals to high-voltage bus terminals, then electrical connection is enabled, but contactors may become welded closed due to high voltage stress

Engineering Contradiction:

Improvecontactor operation reliabilityVSAvoidhigh voltage stress causing weld

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system performs a preliminary weld detection check by monitoring voltage across charger terminals before closing the main contactor. If voltage is detected above a threshold when it should be near zero, the system prevents contactor closure, avoiding the harmful high-voltage stress that causes welding.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors voltage across charger terminals and provides feedback to the controller. This feedback enables real-time detection of abnormal voltage conditions that indicate potential welds, allowing the system to respond by preventing contactor closure and inhibiting vehicle operation.

Inventive Principle:

Principle #23Feedback

2Object-affected harmful factors

If selective isolation elements are used to isolate high-voltage components, then safety is improved, but under abnormal conditions the isolation elements may fail to properly isolate

Engineering Contradiction:

Improveprotection from high voltage hazardsVSAvoidisolation element performance

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

Before enabling high-voltage operation, the system performs preliminary checks to ensure isolation elements are functioning correctly. By detecting voltage conditions that would indicate welds before they occur, the system prevents isolation element failure and maintains safety.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The voltage monitoring system provides continuous feedback on the state of isolation elements. When abnormal voltage conditions are detected, the system responds by preventing contactor closure and inhibiting vehicle operation, ensuring isolation elements maintain their protective function.

Inventive Principle:

Principle #23Feedback

3Reliability

If the precharge contactor is closed to charge the high-voltage bus, then bus voltage is established, but if charger contactors are welded, voltage will be present across charger terminals indicating a fault

Engineering Contradiction:

Improvesafe vehicle operationVSAvoidvoltage monitoring and control logic

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system monitors voltage across charger terminals during the precharge sequence and uses this feedback to detect weld conditions. If voltage is detected when it should be near zero, the system responds by preventing main contactor closure and inhibiting vehicle operation, maintaining safety despite the added monitoring complexity.

Inventive Principle:

Principle #23Feedback

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 and prevents double-welded contactor conditions, ensuring safe operation by inhibiting vehicle operation and preventing battery connection to the high-voltage bus when faulty conditions are detected, thereby maintaining electrical isolation and preventing potential hazards.

Implementation Method 1

monitoring voltage changes across terminals and the high-voltage bus

Methodology Applied

Scientific EffectVoltage measurement: Ohm's Law

Implementation Method 2

command the precharge contactor to close for charging the high-voltage bus to a predetermined bus voltage

Methodology Applied

Scientific EffectElectrical charging: Capacitance

Data Source

PatentUS11299056B2System and method for charger contactor double weld detection

Publication Date: 2022.04.12 FORD GLOBAL TECH LLC

AI summary

A vehicle includes charger contactors configured to selectively electrically couple terminals for connecting to a charger to corresponding terminals of a high-voltage bus. The vehicle includes a precharge contactor configured to selectively couple a terminal of a battery to the high-voltage bus through an impedance element. The vehicle includes a controller programmed to command the charger contactors to an open state for a drive cycle and command the precharge contactor to close at a start of the drive cycle and, responsive to a voltage across the terminals for connecting to the charger changing from being less than a first predetermined voltage immediately prior to the precharge contactor being closed to being greater than a second predetermined voltage at a completion of precharging, inhibit vehicle operation and disconnect the battery from the high-voltage bus.