Understanding Electromagnetic Relays: Types and Applications

Electromagnetic relays are fundamental components in the world of electrical engineering, playing a crucial role in controlling circuits by utilizing a small electrical signal to switch on or off a larger load. This blog post will delve into what electromagnetic relays are, how they work, and the different types available.

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 types of electromagnetic relays are there?

There are several types of electromagnetic relays, but they can be divided into two main types:

Electromagnetic Induction Relay

Electromagnetic Attraction Relay

Electromagnetic induction relay Electromagnetic relays work similarly to a split induction motor. In stages. An initial force is generated on the moving element, which can be a non-magnetic moving element of a disk or other rotor type. The eddy currents induced in the rotor by the electromagnetic flux interact with the magnetic flux to generate a force. Various types of constructions have been used to determine the phase difference of the magnetic flux.

These buildings are –

Shade Pole Construction

Power Meter Construction

Induction Cup Relay

 

 

1.Shaded pole structure

 

Typically, this coil is driven by current through a single coil wound around an air-gapped magnetic structure. The initial flow splits the air-gap flow into two flows, which are shifted in time and space by the shaded rings. A copper ring surrounding part of the pole face of each pole forms the dark ring.

2. Watt-hour meter construction

The construction consists of a freely rotating disk sandwiched between an E-shaped and a U-shaped electromagnet. The magnetic flux produced by the two magnets, which have different resistance and inductance for the two circuits, is used to determine the phase shift between the magnetic fluxes of the electromagnets. The primary and secondary windings are supported by the E-shaped electromagnet. A relay current I1 flows due to the primary current and the secondary winding is connected to the winding of the U-shaped electromagnet.

3.Induction Cup Relay

An induction cup relay is a type of relay based on the theory of electromagnetic induction. Two or more electromagnets in the relay are powered by a relay coil. A stationary iron core is located between the electromagnets.

A rotating magnetic field is generated by a coil wound around the electromagnets. A current in the cup is induced by the rotating magnetic field. The cup will start to spin. The cup will rotate in the same direction as the water flow. Compared to a relay with a shield or wattmeter, the induction cup relay produces more torque. The relay acts quickly and has a very short operating time of just 0.01 seconds.

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Electromagnetic Attraction Relay

The armature of this relay is attracted to the poles of a magnet. The moving element is subjected to an electromagnetic force proportional to the square of the current flowing through the coil. This relay handles both AC and DC currents.

The above equation shows that an electromagnetic relay consists of two parts: a constant component that is time independent and a second component that is time dependent and pulsates at twice the supply frequency. Noise generated by this double the supply frequency will damage the relay contacts.

The challenge of dual frequency supply is overcome by splitting the increasing magnetic flux in an electromagnetic relay. These flows occur simultaneously but with different time phases. As a result, the resulting deflection force is always positive and constant. Flux sharing can be achieved by using electromagnets with a phase-shifting network or by attaching shielding rings to the poles of the electromagnets.

 

 

 

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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The simplest type of relay is the electromagnetic attraction relay, which consists of a moving polarized iron relay, a hinged armature, a rotating armature, and a piston (or solenoid). All these relays are shown below.

Conclusion

Electromagnetic relays are versatile and essential components in many electrical and electronic systems. Understanding the various types of relays and their specific applications can help in selecting the right relay for a given task, ensuring efficient and reliable circuit control. Whether for simple switching, motor control, or complex industrial automation, there's a relay designed to meet the requirements.