In this note, we are going to learn about a topic called “What is Electromagnetic Relay?“, also about its construction, types, working principle, and many more topics. Welcome to Poly Notes Hub, a leading destination for polytechnic notes for diploma engineering students.
Author Name: Arun Paul.
What is Electromagnetic Relay?
An Electromagnetic Relay is an electrical switch powered by an electromagnet. It is made up of a wire coil that, when energized, produces a magnetic field that attracts a movable armature or contact. This movement of the armature or contact activates the relay contacts, opening or closing an electrical circuit.
Electromagnetic relays are widely utilized in a variety of applications, including control systems, automation, telecommunications, and power distribution, to manage high-power circuits using low-power signals. They provide advantages such as quick switching, high reliability, and electrical isolation between the input and output circuits.
There are two types of Electromagnetic Relay –
- Electromagnetic Attraction Type Relay
- Electromagnetic Induction Type Relay
Construction of Electromagnetic Relay
Below we listed some important parts of electromagnetic relays –
📌 Noted: At the above diagram, we are displaying Hinged Armature Type Electromagnetic Attraction Relay.
- Coil: The coil is typically composed of copper wire twisted around a core made of a ferromagnetic substance. When an electrical current flows through a coil, it produces a magnetic field.
- Moving Armature: The moving armature is a movable component often made of ferromagnetic material like iron or steel. When the coil is energized, the magnetic field generated attracts it to the core.
- Core: The core is usually formed of a ferromagnetic material like iron or steel, and it serves to concentrate the magnetic field generated by the coil, boosting its strength.
- Moving Contact: The moving contact is connected to the moving armature. When the armature is attracted to the core, it pushes the moving contact closer to or further away from the fixed contact, depending on the relay’s configuration.
- Fixed Contact: The fixed contact is stationary and typically constructed of a conductive substance like silver or copper. It serves as a point of contact for the moving contact when the relay is triggered.
- Control Spring: The control spring is a spring device that restores the moving armature after the coil is de-energized. It aids in the return of the armature to its original position after the electrical current through the coil is interrupted.
- Stop: The stop is a mechanical component that restricts the armature’s mobility and prevents it from hitting the core or other sections of the relay when powered.
Working Principle of Electromagnetic Relay
When an electrical current is given to the coil, it creates a magnetic field that draws the moving armature to the core. This movement puts the moving contact into contact with the stationary contact, thus completing the electrical circuit. When the electrical current through the coil is turned off, the control spring restores the armature to its original position, breaking the contact between the moving and fixed contacts and opening the circuit.
This technique enables electromagnetic relays to turn electrical circuits on and off in response to changes in electrical current via the coil, making them useful components in a variety of applications.
Advantages of Electromagnetic Relay
Below we listed some important merits of these relays –
- Suitable for a variety of circuits and applications.
- The simple and durable design assures reliable functioning.
- These relays are able to swiftly turn on and off circuits.
- When powered, it consumes relatively little electricity.
- Easily integrated into current systems with minimal adjustments.
Applications of Electromagnetic Relay
Below we listed some applications of these relays –
- Controls motors, pumps, conveyors, and other machinery in manufacturing operations.
- Used in switchgear and distribution panels to regulate the flow of energy in power networks and substations.
- Found in vehicle circuits that regulate lights, fans, wipers, and other electrical components.