Electromagnetic induction and alternating current class 12. What is the difference between elctromechanical relay and. Jun, ding, fan, li, qipe ng, and da, jing, nove l high speed. Electromagnetic relay working types of electromagnetic. Electromagnetic induction theory, application, advantage. Electromagnetic induction was discovered independently by michael faraday in 1831 and joseph henry in 1832. Wind pushes the blades of the turbine, spinning a shaft attached to magnets. Induction cup relay working principle construction and types.
However, the magnitude of the voltage induced is proportional to the inverse of the coil radius. It consist of an electromagnetic system which operates on moving conductors generally in the form of disc or cup function through the interaction of electromagnetic flux. Basic relays electromagnetic attraction and induction relays. The electromechanical relay can be defined as an electrically operated switch that completes or interrupts a circuit by physical movement of electrical contacts into contact with each other. Induction relays electromagnetic induction relays operate on. Electromagneticinduction relays use the principle of the induction motor where torque is developed by induction in a rotor. Electromagnetic attraction relays working,construction. A timevarying electric field can act as source of magnetic field. When a relay coil is deenergized, its electromagnetic field collapses, which induces a brief voltage spike into the coils wire.
When the electromagnetic force is strong enough for the contact to move then it will connect with another cont. When the operating current becomes large, the magnetic field produced by an electromagnet is so high that it attracts the armature or plunger, making contact with the trip circuit contacts. Electromagnetic induction is a process in which an electromotive force voltage is produced across an electrical conductor with varying magnetic fields or magnetic flux. The working principle of electromagnetic relays is not complicated, and it operates mainly according to the principle of electromagnetic induction. Faraday was the first to publish the results of his experiments in 1831 august 29. The force is developed by the interaction of electromagnetic fluxes with eddy current, that is induced in the rotor by these. The basis construction of this relay is just like four poles or eight pole induction motor. An induction type relay is a splitphase induction motor with contacts. An induction relay works only with the alternating current. Electromagnetic induction was discovered by michael faraday in 1831 and james clerk maxwell mathematically described it as faradays law of induction electromagnetic induction is a current produced because of voltage production electromotive force due to a changing magnetic field. It consists of an electromagnetic system which operates on a moving conductor, generally in the form of a disc or cup, and functions through. Switching on the power in the lowvoltage control circuit, the current goes through the coil of the electromagnet to generate a magnetic field. Electromagnetic induction notes for iit jee, download pdf.
The working principle of the mechanical relay is the principle of electromagnetic induction. Here, an aluminum or copper disc is placed between the poles of an ac magnet which produces an alternating flux. Build something learning to analyze relay circuits requires much study and practice. The relay operates when the operating force is greater than the restraining force. Basic electromagnetic relays basic electricity pdf version.
The electromagnetic relay is mainly classified into two types they are electromagnetic attraction relay and electromagnetic induction relay. Electromagnetic induction also known as faradays law of electromagnetic induction or just induction, but not to be confused with inductive reasoning, is a process where a conductor placed in a changing magnetic field or a conductor moving through a stationary magnetic field causes the production of a voltage across the conductor. Electromagnetic attraction relays operate by virtue of an armature being attracted to the poles of an electromagnet or a plunger being drawn into a solenoid. In induction relay the deflecting torque is produced by the eddy currents in an aluminium or copper disc by the flux of an ac electromagnet. Lenzs law describes the direction of the induced field. Almost 200 years ago, faraday looked for evidence that a magnetic field would induce an electric current with this. Principle of induction type relays electrical concepts. The electromagnetic relay operates largely as per the principle of electromagnetic induction, which also means that as the electric current is passed on the conductor, the conductor behaves like a magnet so, as you switch on the power in the lowvoltage control circuit, the. Part of the utility of electromagnetic induction is in its ability to produce a thin build. In these relays, the actuating force is developed by the moving contact which can be a disc or cup through the interaction of two alternating magnetic fluxes on a magnetic element. Electromechanical relays are not the best choice in high frequency switching applications and do have a limited life due to wear on the contacts inside the relay. Electromagnetic induction and faradays law key points induced emf faradays law of induction. A timevarying magnetic field can act as source of electric field. The important types of electromagnetic attraction relays are.
The induction disc type relay is based on the same principle as that of an ammeter or a volt meter, or a wattmeter or a watt hour mater. In this article, we bring you the detailed ncert solutions for class 12 physics prepared by the expert academicians at embibe. It will take much longer time to be replaced the all electromagnetic relays by micro processor based static relays. Modern electrical protection relays are mainly micro processor based, but still electromagnetic relay holds its place. In electromagnetic attraction relays, there is a coil which energises an electromagnet. Thus this topic breaks the misconception of the separate electric and magnetic field and shows that both fields are related to each other in some way. Basic electromagnetic relays worksheet basic electricity. Faradays law electromagnetic induction electrical4u. The two fluxes have the same frequency but are displaced in time and space. An induction relay works only with alternating current. A relay uses an electromagnet to pull a contact against the force of a retaining spring. The number of poles in the protective relay depends upon the number of winding to be accommodated.
Electromechanical relay circuit working with applications. Induction type relays are working on the principle of electromagnetic induction. Maxwell an induced current and emf is generated when. The theory of electromagnetic induction was discovered by michael faraday in the year 1830. When the relay is activated they open, replacing a conductor by a resistor and all the induction current will be dissipated through this resistor. The electrical protective relay can be broad, classified into two categories i electromagnetic relay and ii static relay. The shaded pole structure the watthourmeter structure the induction cup and double induction loop structures the single induction loop structure. The different types of structure that have been used for an induction type relay are commonly called. Ncert solutions for class 12 physics chapter 6 pdf. Electromagnetic relay working types of electromagnetic relays. The conventional types of electromagnetic relays electromechanical relay has one or more coils, movable elements, contact system etc and its operation depends on whether the operating torque or force is greater than the restraining torque or force. This process of electromagnetic induction, in turn, causes. The relay is an electromechanical switch used as a protecting device and also as a controlling device for various circuits, equipments, and electrical networks in a power system.
Since the control variable of this kind of actuator is the electric current fed by the power converter drives, so these can be easily controllable. Induction experiments faraday henry if the magnetic flux through a circuit changes, an emf and a current are induced. As the interaction of alternating fluxes is the base of operation of induction relays, these are not used for the d. These two fluxes which are mutually displaced both in angle and in position. According to the principle of operation and construction, the relay may be classified such as the electromagnetic attraction type, electromagnetic induction type, electrodynamic type, moving coil type, electrothermal. A relay is an electromechanical switch, operated by passing current through a coil of wire wound around a steel core, which acts as an electromagnet, pulling the switch contact down to make or break a circuit. Magnetic flux through a surface of area a placed in a uniform magnetic field b is defined as cos. Electromagnetic or magnetic induction is the production of an electromotive force i. Actuating force is developed in a movable element that may be a disc or other form of rotor of nonmagnetic currentconducting material by the interaction of electromagnetic fluxes with eddy currents that are induced in the rotor by these fluxes.
The shadedpole structure as shown in figure below is generally actuated by current flowing. Practically, a relay is an amplifier, since it is able to control a high power output through a low power input. The fundamental principles that govern electromagnetic actuators are faradays laws of electromagnetic induction, lorenz force of electromagnetic forces and biotsavart law. Class 12 physics revision notes for chapter 6 electromagnetic induction free pdf download. Among other applications, electromagnetic induction has also been used for generating heat in modern stove range tops. This relay in nothing but one version of induction disc relay. Electromagnetic induction electromagnetic transducers convert mechanical motion as produced by, e. So before going through detail of protection relay. Induction cup relay work in same principle of induction disc relay. The electromagnetic relay operates largely as per the principle of electromagnetic induction, which also means that as the electric current is passed on the. The initial force is developed on the moving element that may be disc or another form of the rotor of the nonmagnetic moving element. Download as pptx, pdf, txt or read online from scribd. Electromagneticinduction relays use the principle of the induction motor whereby torque is developed by induction in a rotor. What are the differences between electromechanical relays.
Electromagnetic relays are those relays which are operated by electromagnetic action. Typically, students practice by working through lots of sample problems and checking their answers against those provided by the textbook or the instructor. If you are searching for electromagnetic induction class 12 ncert pdf, then you have landed at the right place. The main presentation is a powerpoint with animated sequences showing the workings and purpose of electromagnetic relays. It is used in a variety of applications, including alarms and sensors, signal switching, and the detection and control of faults on electrical distribution lines. These types of relays are used only with ac source. Michael faraday, was an english physicist who gave, one of the most basic laws of electromagnetism called. Electromechanical relays are an excellent solution to separate electronic control circuitry and power circuitry. The electromagnetic relay operates on the principle of a splitphase induction motor.
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