Magnetically Latched Relays for Automatic Transfer Switches
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Solution Overview
Problem
Standard relays in automatic transfer switches face issues of reduced longevity due to continuous energization, which leads to heat generation and premature failure, and produce unacceptable on-off voltage waveforms that can disrupt sensitive electronic loads.
Innovation Solution
The use of magnetically latched relays that are held in open or closed states by permanent magnets, eliminating the need for continuous energization and reducing contact bounce by requiring coil energization only for state changes, thus minimizing exposure to heat and eliminating multiple voltage crossings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard relays are continuously energized to maintain relay operation, then the relay can maintain its switching state, but the relay coil generates heat leading to premature failure and reduced reliability
Solution Approach 1:
The patent employs magnetically latched relays that use periodic pulsing of the coil instead of continuous energization. The coil is energized only momentarily to change the state of the relay contacts, after which a permanent magnet maintains the contact position without requiring continuous electrical power. This periodic action eliminates continuous heat generation while maintaining relay functionality.
Solution Approach 2:
The patent introduces a permanent magnet as an intermediary element that takes over the holding function from the electromagnetic coil. Once the coil energizes the armature to change contact state, the permanent magnet provides the continuous holding force, allowing the coil to be de-energized. This intermediary mechanism separates the switching function (electromagnetic) from the holding function (magnetic latching).
2Ease of operation
If standard relays are used for transfer switching, then the relay can switch between power sources, but the relay produces multiple on-off voltage waveforms that disrupt sensitive electronic loads
Solution Approach 1:
The magnetically latched relay uses controlled periodic energization of the coil only when state changes are required, rather than continuous operation. This results in clean, single-transition voltage waveforms instead of multiple on-off fluctuations, because the contacts move decisively in one direction only when energized, and remain stable when de-energized under permanent magnet influence.
Solution Approach 2:
The patent replaces the continuous electromagnetic mechanical system with a magnetic latching system that uses permanent magnets for holding. This substitution eliminates the continuous electromagnetic attraction and release cycles that cause contact bounce and multiple voltage transitions, providing cleaner switching with fewer voltage waveform disruptions.
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 solution enhances the reliability and durability of automatic transfer switches by preventing continuous coil energization and reducing contact bounce, ensuring stable operation of critical electronic loads without premature relay failure or voltage disruptions.
Implementation Method 1
magnetically latched relays that are held in open or closed states by permanent magnets
Implementation Method 2
requiring coil energization only for state changes
Data Source
AI summary
An automatic transfer switch includes first and second magnetically latched relays that respectively connect first and second voltage sources to a critical load. The first and second relays are magnetically latched in their respective opened or closed positions by a permanent magnet so that no holding current is supplied to the relays after switching is completed. As such, no holding current is required for either relay in the non-transferred or the transferred state of the automatic transfer switch, which reduces heat generated by the relays which can lead to relay failure. A switching method uses the automatic transfer switch to switch voltage sources without requiring relay holding currents in either the non-transferred or transferred state. A method of reducing contact bounce is also disclosed.