Electromechanical Relay Coil Circuit for Fast Closing
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Solution Overview
Problem
Electro-mechanical relays in protective relays for power distribution systems have a delayed turn-on time and significant contact bounce, which is not sufficient for applications requiring faster responses, such as arc flash protection.
Innovation Solution
A circuit structure is introduced that includes a coil with first and second resistors in series, where a first switch is used to short out the second resistor and provide a high current to quickly close the relay contact, and then a second switch turns off the first switch to maintain the contact in the closed position with a reduced current, utilizing MOSFETs and a timing circuit to control the current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high current is applied to the coil to reduce closing time, then the closing speed is improved, but contact bounce increases
Solution Approach 1:
The patent applies periodic action by using a two-stage current waveform: first a high current pulse to quickly close the contact, then a reduced maintenance current to hold the contact closed. This time-varying current approach allows the system to achieve fast closing without continuously applying high current that would exacerbate bounce
Solution Approach 2:
The patent implements dynamics by making the coil current variable rather than static. The current dynamically changes from a high initial value to a lower maintenance value, allowing the magnetic force to be sufficiently high only during the critical closing transition period, thereby reducing contact bounce while maintaining fast closing speed
2Force
If more turns or more current is applied to the coil to increase magnetic force, then the magnetic force is improved, but the turn-on time increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the current parameter through a two-stage waveform. The first stage uses high current to generate sufficient magnetic force for fast actuation, while the second stage uses reduced current to maintain the magnetic force at a lower level, thereby achieving both strong magnetic force and fast response without the trade-off of increased turn-on time
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 reduces the closing time of electro-mechanical relays to approximately 1 mS while maintaining a similar bouncing time of 2 mS, addressing the need for faster response without increasing contact bounce.
Implementation Method 1
When current is applied to the coil of the relay, a magnetic force is developed. This magnetic force is determined by the amps multiplied by the turns of the coil.
Implementation Method 2
A first resistor and a second resistor are each in series with the coil, with the second resistor being in parallel with a first switch. A voltage is provided to the first switch, with the first switch being ON, thereby shorting out the second resistor and providing a first current through the first resistor and to the coil
Implementation Method 3
This magnetic force then pulls a lever, which is inside of the relay, to the coil. The lever, in turn, moves output contacts of the relay to either open, close (or both open and close), depending on the construction of the relay.
Data Source
AI summary
A method of increasing speed of an electro-mechanical relay provides an electro-mechanical relay having a coil and at least one contact. A first resistor and a second resistor are each in series with the coil, with the second resistor being in parallel with a first switch. A voltage is provided to the first switch, with the first switch being ON, thereby shorting out the second resistor and providing a first current through the first resistor and to the coil, to move the contact to a closed position. After a certain amount of time, the first switch is turned OFF so that a second current is provided through the first and second resistors and to the coil, maintaining the contact in the closed position.