What Is an Electromagnetic Relay?
An electromagnetic relay is an electrically operated switch that is used to control a circuit by an electromagnetic mechanism. It consists of a coil of wire, a movable armature, and one or more sets of contacts. When a current flows through the coil, it creates a magnetic field that activates the armature and moves it to open or close the contacts, allowing or interrupting the flow of current in the circuit. Electromagnetic relays are commonly used in control systems and electrical circuits to isolate, amplify, and switch electrical signals.
What Are the Uses of Electromagnetic Relay?
Electromagnetic relays are used in a wide variety of applications, including electrical and electronic circuits. Some of the most common uses of electromagnetic relays include the following:
Control circuits: Electromagnetic relays are often used in control circuits, where they are used to switch electrical signals on and off in response to a control signal. For example, an electromagnetic relay might be used to control the flow of electricity to a motor, allowing it to start and stop in response to a signal from a controller.
Protection circuits: Electromagnetic relays are also used in protection circuits, where they are used to interrupt the flow of electricity in the event of an overcurrent or other fault condition. This helps to prevent damage to electrical equipment and prevent accidents.
Amplification: Electromagnetic relays can be used to amplify electrical signals by switching them on and off rapidly. This is often used in radio and other communication systems, where the relay can be used to switch between different antennae or transmitters.
Timing: Electromagnetic relays can be used in timing circuits, where they are used to switch circuits on and off at specific intervals. This can be used in a variety of applications, such as controlling the timing of streetlights or other electrical devices.
Overall, electromagnetic relays are an important component in many different electrical and electronic systems and are used in a wide range of applications.
What Are the Types of Electromagnetic Relay?
There are multiple electromagnetic relay types, but they can primarily be divided into two main types –
Electromagnetic Induction Relay
Electromagnetic Attraction Relay
Electromagnetic Induction Relay
The electromagnetic relay functions similarly to an induction motor with split phases. On the moving element, which might be a disc or another type of rotor of the non-magnetic moving element, the initial force is created. Eddy current, which is induced in the rotor by the electromagnetic fluxes, interacts with the fluxes to create the force.
To determine the phase difference in the fluxes, various types of structures have been used. These buildings are
- Shaded pole structure
- Watt-hour Meter Structure
- Induction Cup Relay
Shaded Pole Structure
Typically, this coil is powered by the current passing through the single coil coiled on a magnetic construction with an air gap. The initializing current splits the air-gap fluxes into two fluxes that are displaced in time and space by a shaded ring. The copper ring that surrounds a portion of each pole's pole face forms the darkened ring.
Aluminum makes up the disc. The aluminum disc has relatively little inertia. Therefore, they require less deflecting torque to move. The electromagnetic flux's alternating flow induces a current in the two rings. The flux in the area of the iron ring that is encircled by the ring lags in phase by 40° to 50° behind the flux in the region of the pole that is not shadowed by the ring due to the magnetic field that forms from the current.
Watt-hour Meter Structure
A disc free to rotate is sandwiched between an electromagnet in the E shape and an electromagnet in the U shape that make up this construction. The flux created by the two magnets with varied resistance and inductance for the two circuits is used to determine the phase displacement between the electromagnet's fluxes.The primary and secondary windings are carried by the E-shaped electromagnet. The relay current I1 was carried by the primary current, and the secondary winding was connected to the U-shaped electromagnet's windings.
Relay current I1 is carried by the primary winding, and I2 is circulated in the secondary winding as a result of the secondary current's induction of an emf. Both flux 1 and the flux induced in the U-shaped magnet and the E shed magnet, respectively. These fluxes, which are induced in the upper and lower magnetic layers, are phase-differentiated by an angle, and this causes a driving force on the disc that is proportional to 1 sin. The relay's ability to open or close the secondary winding circuit and control operation is its most crucial function. By opening the secondary winding, no torque will be created, rendering the relay inoperable.
Induction Cup Relay
The induction cup relay is a type of relay that operates on the electromagnetic induction theory. Two or more electromagnets in the relay are powered by the relay coil. Between the electromagnet is where the static iron core is located.
The spinning magnetic field is produced by the coil that is wound on the electromagnet. The current in the cup induces due to the revolving magnetic field. The cup so begins to rotate. The cup rotates in the same direction as the current does. In comparison to shaded and watt meter type relays, the induction cup relay produces more torque. The relay operates quickly and has a very short operating time of only 0.01 seconds.
Electromagnetic Attraction Relay
The armature of this relay is drawn to the magnet's pole. The moving element is subjected to an electromagnetic force that is proportional to the square of the current flowing through the coil. Both the alternating and direct currents are handled by this relay.
The aforementioned equation demonstrates that the electromagnetic relay is made up of two parts: a constant component that is independent of time, and a second component that depends on time and pulses at a double supply frequency. Due to the noise that this double supply frequency generates, the relay contacts are harmed.
By dividing the flux that is growing in the electromagnetic relay, the challenge of a double-frequency supply is overcome. Although occurring simultaneously, these fluxes have different temporal phases. As a result, the deflecting force that results is always positive and steady. By employing an electromagnet with a phase-shifting network or by attaching shading rings to an electromagnet's poles, flux splitting can be accomplished.
The simplest sort of relay is the electromagnetic attraction relay, which consists of a movable iron polarized relay, a hinged armature, a rotating armature, and a plunger (or solenoid). These relays are all displayed below.
Balanced Beam Relay
By comparing two values because the electromagnetic force it develops changes with the square of the ampere-turn. Such relays have a low operating current ratio. The relay will tend to overshoot on a quick operation if it is configured for fast operation.
Hinged Armature Relay
By including a permanent magnet, the sensitivity of the relay can be raised for DC operation. The polarized moving relay is another name for this relay.
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