Relay Coil Voltage Monitoring for Welded Contact Detection

Solution Overview

Problem

Switching devices used in industrial and commercial settings often experience contact welding due to excessive start-up current or bouncing, leading to electrical and mechanical issues such as failure to disconnect power from loads, which can cause safety hazards and operational inefficiencies.

Innovation Solution

A system and method that includes a control system to detect whether contacts of a switching device are at least partially welded by measuring voltage responses when a fixed current or voltage profile is applied to the relay coil, allowing for non-intrusive detection without powering the relay coil or relying on sensors, and subsequently controlling the power supply to prevent welding issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If voltage measurements are taken during the period the coil is powered to detect welded contacts, then detection accuracy is improved, but energy consumption increases and contact welding risk increases

Engineering Contradiction:

Improvewelded contact detection accuracyVSAvoidcontact welding risk

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The system performs welded contact detection during the period when the coil is already powered, before the armature actually closes the contacts. This preliminary detection allows the control system to identify welded contacts early and prevent further damage by disconnecting power before the harmful welding effect occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control system continuously monitors voltage measurements across the coil during operation and uses this feedback to detect welded contacts. When the voltage pattern indicates a welded contact, the system responds by disconnecting power to the coil, creating a closed-loop control system that prevents damage.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If voltage measurements are taken during the period the coil is powered to detect welded contacts, then detection accuracy is improved, but energy consumption increases

Engineering Contradiction:

Improvewelded contact detection accuracyVSAvoidcoil power consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The system performs welded contact detection during the period when the coil is already powered, before the armature actually closes the contacts. This preliminary detection allows the control system to identify welded contacts early and prevent further damage by disconnecting power before the harmful welding effect occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control system continuously monitors voltage measurements across the coil during operation and uses this feedback to detect welded contacts. When the voltage pattern indicates a welded contact, the system responds by disconnecting power to the coil, creating a closed-loop control system that prevents damage.

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

Enables the detection of welded contacts in a non-intrusive manner, reducing electrical and mechanical safety issues and improving switching device performance without adding complexity, allowing for safe and reliable operation by preventing welding of contacts.

Implementation Method 1

The switching device may also include a coil that may receive a current from a second power source, thereby causing the armature to electrically couple the movable contacts to the contacts of the electric circuit or electrically disconnect the movable contacts form the contacts

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11901145B2Systems and methods for detecting welded contacts in an electromagnetic switch system

Publication Date: 2024.02.13 ROCKWELL AUTOMATION TECH INC

AI summary

A non-transitory, computer-readable medium may include instructions executable by at least one processor in a computing device to cause the processor to perform operations that include transmitting, to a first power source, a command to provide power to a coil of a switching device with a fixed current profile. The operations also include receiving one or more voltage measurements associated with the coil during a period of time, determining whether the voltage measurements associated with the coil indicate that one or more movable contacts of the switching device are at least partially welded to one or more contacts of an electric circuit, and transmitting an additional command to a second power source to disconnect a current to the coil in response to determining that the voltage measurements indicate that the movable contacts of the switching device are at least partially welded to the contacts of the electric circuit.