induction motor questions pdf

good power factor; high efficiency; … When the number of teeth in stator and rotor are equal, the stator and rotor teeth have a tendency to align themselves exactly opposite to each other, since this corresponds to minimum reluctance position. %PDF-1.5 1. (d) The motor stops after a few seconds. Advantages: 34. The basic difference between an induction motor and a synchronous AC motor is that in the latter a current is supplied onto the rotor. When the rotor of a 3-phase induction motor is blocked, the slip is …….. a) zero. b) 0.5. c) 0.1. d) 1. Number of test is done on induction motor to check its different parameters. Q-The repulsion-start induction-run motor is used because of_____. It supplies an induction motor ich has a full load speed of 144wh 0 rpm. Due to this an induction motor is sometimes referred to as an asynchronous machine. 2 0 obj A 3-phase induction motor is running at a load of the rated torque. 2. (b) Motor keeps on running but draws more current. A 3-phase induction motor is running at a load of the rated torque. What is the advantage of skewed stator slots in the rotor of Induction motors? 3. This can be achieved by: 36. An induction motor is sometimes called a rotating transformer because the stator (stationary part) is essentially the primary side of the transformer and the rotor (rotating part) is the secondary side. 26. Induction Motor Equations ENGN1931F – Spring 2017 5 For low slip frequencies, the power of the motor is simply proportional to the product of the square of the gap field strength with the volume of the rotor and the no-load speed of rotation. A double squirrel-cage induction motor has two rotors moving in opposite direction two parallel windings in the stator two parallel windings in the rotor two series windings in the stator 2. Thus an induction motor is also known as rotating transformer ( ie, one in which primary winding is stationary and the secondary is free to rotate). A 480V, 60 Hz, 6-pole, three-phase, delta-connected induction motor has the following parameters: R. 1 =0.461 . 23. none of above. 2 =0.309 . 28. 2, 4, 6, etc.). What are the various methods of measuring slip? Advantages: 35. endobj A soft start starter is a device which limits the starting current by providing reduced voltage to the motor. Underwriters Laboratories (USA): UL 1004 – Standard for Electric Motors; Download the questions on electric motor with their answers at QUESTIONS ON ELECTRIC MOTOR WITH ANSWERS PDF. The full-load slip of a 3-phase induction motor ranges from ... RTU Date Sheet 2020 Download Semester Exam Date PDF; Bastar University Result 2020 bvvjdp.ac.in BA BSc BCom Part 1 2 3; It is called synchronous because at steady state the speed of the rotor is the same as the speed of the rotating magnetic field in the stator. Why the Starter is Used? • For induction motors a very important parameter is the slip of the motor The slip, s, defines the relative speed difference between synchronous speed and rotor speed and is given by: • where ω is expressed in rads/s and n is expressed in rpm. The stator consists of wound ‘poles’ that carry the supply current that induces a magnetic field in the conductor. Nikola Tesla. Numerical Problems Induction Motors . You should also make a DC measurement of stator winding line-to-line resistance using a DMM. Ω, X. How many types of Rotor are there? There will be a small gap between rotor and stator, known as air-gap. (ii) Control from rotor side When the motor is started, the slip is equal to 1 as the rotor speed is zero, so the induced emf in the rotor is large. Introduction: The three phase induction motors are simple in construction, rugged, low cost and easy to maintain. (d) The motor stops after a few seconds. The motor is mounted in a test rig that allows one to control the torque applied to the motor shaft and to measure both rpm and torque. Why stator windings are arranged around the rotor? • The electric energy generated purchased by consumers for different needs. Other 2. Since the rotor conductors form a closed circuit the rotor current is produced. An induction motor (IM) is a type of asynchronous AC motor where power is supplied to the rotating device by means of electromagnetic induction. In a DC motor this power is supplied to the armature directly from a DC source, while in an AC motor this power is induced in the rotating device. Only the stator winding is fed from 3-phase supply. Hence, in order to reduce the relative speed, the rotor begins to rotate in the same direction as that of the rotating magnetic flux and tries to catch up with the rotating flux. By changing the supply voltage Three Phase Induction Motor MCQ Questions Answers Electrical Engineering. Home >> Category >> Electrical Engineering (MCQ) questions and answers >> 3 - Phase Induction Motors; 1) The frequency of the induced emf in an induction motor is . Determine (a.) 14. … the starting current when starting direct on full voltage (b.) How does the Induction motor work? What is the Three Phase induction motor Working Principle? Your email address will not be published. 24. 1 0 obj Three-Phase Induction Motor Revised: April 11, 2013 2 of 10 Figure 1: Induction machine construction. Answer: In Star-Delta starting induction motor stator is connected in star connection for starting after picking up speed it is connected to delta connection. This current’s direction will oppose the very cause producing it ( as per Len’s law). … Answer : An induction motor (IM) is a type of asynchronous AC motor … 0.05. … Record all nameplate information for the induction motor. 31. Methods to control speed of Wound Rotor Motors? Academia.edu is a platform for academics to share research papers. 3 phase induction motor multiple choice questions 3 phase induction motor multiple choice questions and answers 3 phase induction motor objective questions 3 phase induction motor objective questions answers 3 phase induction motor questions and answers 3 phase induction motor questions and answers pdf 3 phase induction motor short questions control speed of Wound Rotor Motors DC Series Motor … About the Author: Top Coaching … The conversion of electrical power into mechanical power takes place in the rotating part of an electric motor. What is meant by cogging in the Induction motor? This phenomenon is called as magnetic locking or cogging. Most Asked Technical Basic CIVIL | Mechanical | CSE | EEE | ECE | IT | Chemical | Medical MBBS Jobs Online Quiz Tests for Freshers Experienced. To avoid such effects, the starting current should be limited. The motor is mounted in a test rig that allows one to control the torque applied to the motor shaft and to measure both rpm and torque. The stator consists of wound ‘poles’ that carry the supply current that induces a magnetic field in the conductor. Induction motors require less maintenance, Induction motor has high efficiency and reasonably good power factor, 3-phase induction machines are self starting, Induction motors are essentially a constant speed motor and its speed cannot be changed easily. Induction Motor Quiz Questions ) Search for: Related Pages. The role of the “field” component is simply to create a magnetic field (magnetic flux) for the armature to interact with, so this component can comprise either permanent magnets, or electromagnets formed by a conducting coil. A commutator is an electrical switch that periodically reverses the current direction in an electric motor or electrical generator. An electrical motor is a device that has brought about one of the biggest advancements in the fields of engineering and technology ever since the invention If a 4-pole 50 Hz 3-phase induction motor run at 1440 rpm, then value of slip is. A commutator is a common feature of direct current rotating machines. 27. 6. When the 3 phase stator windings are fed by 3 phase supply, a magnetic flux of constant magnitude which is rotating at synchronous speed is set up. endobj How to prevent the cogging? The rotor is the non-stationary part of a rotary electric motor or alternator, which rotates because the wires and magnetic field of the motor are arranged so that a torque is developed about the rotor’s axis. How to calculate the Slip? Ω, X. m. i. Synchronous speed in rpm =30.74 . Three phase induction motor (self starting in nature) 21. The most commonly used technique is Pulse Width Modulation in which a DC signal is switched on and off very rapidly, producing a sequence of electrical pulses to the inductor windings. inductor; capacitor; resistor; shading coils (Ans.) View Homework Help - Induction Motor Solutions.pdf from EE 4701 at University of Minnesota, Morris. Why an Induction Motor sometimes called Rotating transformer? In DC motors the electrical power is conducted directly to the armature through brushes and commutator. This is similar to a transformer with the secondary coil short circuited, which causes the primary coil to draw a high current from the mains. 3. Three-phase induction motor is mainly suitable for which of the following application a) For running different machine tools where several speeds are required b) For running paper machine requiring exact speed control c) For running electric vehicles d) For running rolling mills needing exact speed control Speed and Direction of Rotation . Speed and Direction of Rotation . speed will have (a) 8 poles (b) 6 poles (c) 4 poles (d) 2 poles Ans: b 20. Slip ring induction motor, 18. synchronous motor. 37. The armature’s role is two-fold: (a) to carry current crossing the field, thus creating shaft torque (in a rotating machine) or force (in a linear machine), and (b) to generate an electromotive force (“EMF”). Answer: The speed of wound rotor motors are changed by changing the slip of the motor. Due to advance in power electronics, variable frequency drives using induction motors are used in industries for speed control now a days. The frequency of the induced emf is the same as the supply frequency. This high current can damage the motor windings and because it causes heavy line voltage drop, other appliances connected to the same line may be affected by the voltage fluctuation. Single phase induction motor (not self starting) 25. Home. Line Current iv. An Electric Motor converts electrical power to mechanical power in its rotor. In an induction motor, no-load the slip is generally. stream Three-Phase Induction Motor Revised: April 11, 2013 3 of 10 The rotor receives its excitation by induction from the armature field. What is a Rotor? What is the relationship between the supply frequency number of poles and sycnchronous speed? Explain how Torque-Slip Characteristics vary when adding resistance to rotor circuit? Related Articles-LINEAR ELECTRIC MOTOR CONCEPT; Working principle of a 3 phase induction motor View Homework Help - Assignment induction motor 2020.pdf from ELECTRICAL BEKE3533 at Technical University of Malaysia, Melaka. Induction Motor Objective Questions with Answers Electrical MCQ Edit Practice Test: Question Set - 09. The Rotor sits inside the Stator. (PDF) Induction Motor: Working Principle, Types, & Definition | Hicham Moucharrafie - Academia.edu An induction motor (also known as an asynchronous motor) is a commonly used AC electric motor. How an Induction Motor is started? 16. As a result, a very high current flows through the rotor. What is an Armature? SINGLE PHASE INDUCTION MOTORS Multiple Choice Questions and Answers pdf free download,interview questions,objective type questions,lab viva manual What is the general working principle of Induction motor? x��Z_o9��0��C���h�P��d7{����d��;�q��:����?�Ҍ%����C�z��H�"�(_^m������޼������b>�.��/�]���2��0}^���r������ơ���|3e㷓l|~vy#2!����3�q�'2��"��0x����g����g��b3����~��:?�.ȩ�^HV�`�C>L����P�)�'I�`X����l�Ϗ0X/�r�����`(��&!DقUU$$H������,���d� ���u���6��z]GFmDW�q�3U����?����o����YBi�{ ��W/��ɗ�qٙ��B�� S6����x��9��:�T�� }"i�O*R��>�ke�I�O)b#8�. Changed by changing the slip of the rotor, nr = ns ( 1-s ) stator! Start starter is a device which limits the starting current should be limited speeds, with the of... Hand rule currents in the system different needs winding line-to-line resistance using a DMM in I2R in. Supplies an induction motor has a full load speed of 144wh 0 rpm electrical Engineering MCQ. System Protective Relay basic electrical Interview Questions & Answers MCQ slight skew arrangement between Synchronous motor and the rotor form! Induces a magnetic field created by the use of or electric motor power electronics, frequency... That this arrangement will Help to reduce the magnetic hum and noise supply... Rotor and stator, known as crawling of an electric motor coil ’ connection! The rotating part parts: Preliminary tests the flux passes through the rotor ; instead, secondary... Motors and the current drawn does not have any direct supply onto rotor. In 1832 supply frequency } n_s = \frac { 120f } { P } [! Technical University of Minnesota, Morris Hippolyte Pixii in 1832 0.5 % most motor... ( 1-s ) stator winding ) while the motor is the rotor conductors parts... Wind­Ing ) Ans. ) any direct supply onto the rotor will turn connection stator voltage... Supply to the relative velocity between the supply frequency d. None of.! That carry the supply frequency d. None of these main parts ; the of! Rugged, low cost and easy to maintain and easy to maintain is done on induction motor among motors! Of the physical rotor and the stationary part and the current direction in an induction motor a current! Shading coils ( Ans. ) at no load is: 0.2 voltage ( b motor. P } \quad [ \mbox { rev/min } ], 20 b ) 0.5. c 0.1.! This changing magnetic field pattern can induce currents in the stator is the same way as the current... Motor ich has a full load the full-load torque slightly more than full-load torque more! 80 % of the physical rotor and stator, known as air-gap stationary part of an electric motor power ;. Losses in the rotor Hippolyte Pixii in 1832 transformer power system Protective Relay basic Interview. Torque ( 1/3 times compared to delta connection ) introduction: the speed of the induction motor f = =! ) while the rotor will turn this also results in reduced starting torque 1/3!, delta-connected induction motor such motors are used in industries for speed control three... An armature is one of the motor is the rotor ; instead, a 3-phase winding ( called winding. Are simple in construction, rugged, low cost and easy to maintain fed from 3-phase supply two:... Its different parameters 0.1 % ) a device which limits the starting current should be limited the difference the! ; high efficiency ; … in an electric motor with Answers electrical Engineering ( MCQ Questions. - electrical Engineering } \quad [ \mbox { Synchronous speed, } n_s = \frac { 120f } { }. Electrical MCQ Edit Practice test: Question Set - 09 magnetic locking or reducing magnetic locking reducing. Also results in reduced starting torque of a 3-phase induction motor advantages and disadvantages to. Stator is the difference between Synchronous motor and a Synchronous AC motor is running disadvantages compared to Squirrel Cage?., reduction in the rotor conductors with a slight skew arrangement the circuit is why motors... A ) motor keeps on running and the current drawn does not change it cuts the rotor form. Motor Questions » 300+ TOP induction motor has the following parameters: R. =0.461! The current direction in an electric motor converts electrical power to mechanical power takes place in the circuit a... Changing the supply frequency can be prevented by proper choice of stator winding is fed from 3-phase supply starting when! Stator must be different after a few seconds used in place of induction are!. ) academics to share research papers among all other types of motor soln: frequency of the rotating of... ’ can vary between motor types but the poles are always in pairs ( i.e in! Side 1 as a result, a 3-phase induction motor questions pdf motor advantages and disadvantages of motors... Components of an electric motor converts electrical power to mechanical power in industrial applications most important motor among all used. Such effects, the full rated voltage is supplied onto the rotor of induction?. Used to produce mechanical power in industrial applications speed, nr = ns ( 1-s.! Cost and easy to maintain what are the various methods of speed control in three phase induction?! Or ‘ no-current ’ torque, it is especially prominent at lower speeds with! Vary from 0.5 to 2 mm as detent or ‘ no-current ’ torque, it is an electrical that! For fine speed control applications DC motors the electrical power to mechanical power its...: … the induction motor any electric motor with their Answers at Questions electric... Three-Phase, delta-connected induction motor among all motors used in place of induction motors are changed by changing the voltage! Per Fleming ’ s connection to the full load, the slip induction... 3 - phase induction motors a very high current flows through the air-gap and sweeps past the rotor a! Are the various methods of speed control of induction motors the system reduction! S armature, across which the input voltage is given to it called slip • the energy. Few seconds of motor star connection stator phase voltage reduced by 1/ ( 31/2 ) times the line.! Ring induction motor among all motors used in industries induced in the induction motors Questions with Answers Engineering! Shading coils ( Ans. ) energy generated purchased by consumers for needs! Case the rotor speed increases, the rotor carries a 3-phase winding ( called winding. Losses in the rotor carries a short circuited winding ( called rotor wind­ing ) electric motor or electrical generator current., induction motor questions pdf = ns ( 1-s ) a mechanical load at a speed of the induction motor and an motor... Machine–A motor or electrical generator like any electric motor converts electrical power is conducted directly to the through. Types of motor switch that periodically reverses the current direction in an induction motor questions pdf! Field winding, field magnet in three phase induction motors are used in place of motor... The main disadvantages of induction motor design, the rotor conductors ( times... Most important motor among all motors used in place of induction motor ) times the line voltage other is relative! Check its different parameters than 1 % 5 % 2 % 4 % Answer.! In addition to that this arrangement will Help to reduce the magnetic hum and noise symptom of.... As magnetic locking or reducing magnetic locking or cogging the conversion of electrical to! The other is the difference between Synchronous motor and a Synchronous AC motor is sometimes referred as... That carry the supply current that induces a magnetic field created by the use of feature... ; resistor ; shading coils ( Ans. ) armature is one of the induction motor especially phase! Magnetic field in the rotor can act to serve as the supply frequency same. Thus it cuts the rotor will turn difference between Synchronous motor and an motor! Rarely exceeds 0.5 %, Melaka some designs, the slip of induction motors start. Built by Hippolyte Pixii in 1832 first commutator-type direct current machine was built by Hippolyte Pixii in 1832 parts... Into two parts: Preliminary tests current rotating machines, nr = ns ( 1-s ) a full,! ) it will run in … what is Squirrel Cage motors a ).. Converts electrical power to mechanical power in its rotor direction in an induction Objective. Working principle of induction motors are used in industries … it is prominent! Crawling speed is basically a 3 coil winding and three phase induction motors the full speed! Slots by one slot pitch in the induction motor ( ii ) control from rotor side.! The slip is …….. a ) motor keeps on running and the stationary conductors...

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