Relay Contact Arc Inducing Apparatus for Cleaning
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Solution Overview
Problem
In power relays, especially those used in induction motors, currents above the predefined arc current can cause contact arcing, which cleans the contacts but in applications where currents are below this threshold, sulfidation, oxidation, and contaminants form, leading to circuit malfunctions due to lack of arcing.
Innovation Solution
A resistor-capacitor (RC) circuit is coupled to the relay contacts to store energy and provide a current greater than the arc current during a contact bounce, inducing arcing even when the relay current is below the defined arc current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the relay current is kept below the predefined arc current to avoid excessive arcing, then energy loss and contact erosion are reduced, but sulfidation, oxidation, and contaminants form on the contact surfaces leading to circuit malfunction
Solution Approach 1:
The patent applies periodic action by introducing arc cleaning pulses at specific intervals during relay operation. The controller periodically generates high current pulses that exceed the arc current threshold, creating controlled arcing events that clean the contact surfaces. This periodic cleaning action removes sulfidation and oxidation buildup without requiring the relay to operate continuously at high currents, thus resolving the contradiction between energy efficiency and contact reliability.
Solution Approach 2:
The patent implements preliminary action by proactively cleaning the relay contacts before contamination reaches a critical level that would cause malfunction. The controller monitors contact resistance or operates on a predetermined schedule to trigger arc cleaning pulses in advance, preventing the formation of insulating contaminant layers. This preliminary cleaning maintains circuit continuity without requiring excessive current during normal operation.
2Reliability
If contact arcing is induced to clean relay contacts, then sulfidation and oxidation are removed, but the relay may experience excessive wear and reduced lifespan
Solution Approach 1:
The patent applies partial action by using controlled arcing pulses that exceed the minimum current needed for cleaning but are limited in duration and frequency. The controller generates high current pulses only for brief periods during contact bounce or on a scheduled basis, rather than maintaining continuous high current. This partial application of excessive current achieves thorough contact cleaning while limiting cumulative thermal and mechanical stress on the contacts, thereby extending relay lifespan.
3Reliability
If the relay operates with high current to ensure arcing for contact cleaning, then contact surfaces remain clean, but energy consumption increases and the relay cannot be used in low-power applications
Solution Approach 1:
The patent resolves this contradiction by implementing periodic arc cleaning instead of continuous high-current operation. The controller activates high current pulses only periodically—either during contact bounce events or on a predetermined schedule—to clean the contacts. During normal operation, the relay functions at low current levels appropriate for the application. This periodic intervention maintains contact cleanliness without sustaining high energy consumption.
Solution Approach 2:
The patent enables self-service by utilizing the relay's own contact bounce phenomenon to trigger cleaning arcs. When contacts open and close, the natural bounce creates brief moments where the contacts separate and re-connect. The controller detects these bounce events and activates high current pulses during the separation phase, using the existing mechanical motion to facilitate the cleaning action. This eliminates the need for separate high-power cleaning mechanisms.
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
This method effectively cleans relay contacts by generating arcing conditions, preventing the formation of sulfidation, oxidation, and contaminants, thus maintaining circuit continuity and preventing relay malfunctions.
Implementation Method 1
coupling a resistor-capacitor (RC) circuit to a contact of the relay, the RC circuit comprising at least one resistive device and at least one capacitor. The method also includes configuring the RC circuit to store energy when the contacts are closed and to provide current to the relay during a contact bounce
Implementation Method 2
An electric discharge, referred to herein as contact arcing, occurs between contacts within a mechanical power relay when a voltage and a current present at the contacts are above predefined levels and the contacts are switched between a closed position and an open position. Arcing can be beneficial as it removes sulfidation, oxidation, and/or contaminates from surfaces of the relay contacts
Data Source
AI summary
An electric motor that includes a contact arc inducing apparatus is described. The electric motor includes an input terminal configured for coupling with a relay that includes contacts that are electrically coupled when closed and separated by an air gap when open. The input terminal configured to receive power from the relay when the contacts are closed, wherein a predefined arc voltage and arc current facilitate an electric discharge across the contacts when the contacts are transitioned from closed to open. The contact arc inducing apparatus is coupled to the input terminal and configured to provide to the input terminal a current greater than the arc current of the relay and a voltage greater than the arc voltage of the relay during a contact bounce.