Induction motors always operate under lagging power factor and during light load conditions they operate at very worst power factor (0.2 to 0.4 lagging). 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. Depending on the configuration of a spinning electromotive device the stator may act as the field magnet, interacting with the armature to create motion, or it may act as the armature, receiving its influence from moving field coils on the rotor. The induction motor rotor is a completely short-circuited conductive cage. 4. synchronous motor. What Is An Induction Motor? As a result, a very high current flows through the rotor. 26. Where does the power go? Home; Electrical Theory. 27. 32. A soft start starter is a device which limits the starting current by providing reduced voltage to the motor. Three-Phase Induction Motor Revised: April 11, 2013 3 of 10 The rotor receives its excitation by induction from the armature field. 1 =0.507 . %���� 1. induction motor has the following equivalent circuit parameters: Rw1 = 0.25S Rw2N = 0.2S Xl1 = Xl2N = 0.5S Xm1 = 30S The rotational losses are 1700W. View Homework Help - Induction Motor Solutions.pdf from EE 4701 at University of Minnesota, Morris. The non-stationary part on an electric motor is the rotor. All the tests are divided into two parts: Preliminary Tests. 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 slip of induction motor at no load is: 0.2. %PDF-1.5 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. By changing the number of stator poles In such case the rotor may refuse to accelerate. Only the stator winding is fed from 3-phase supply. These currents interact with the rotating magnetic field created by the stator and the rotor will turn. 11. 2 =0.309 . (d) The motor stops after a few seconds. 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. By changing the supply frequency What is a Synchronous Speed? inductor; capacitor; resistor; shading coils (Ans.) It will not be parallel to the shaft. 2. 3. An armature is one of the two principal electrical components of an electromechanical machine–a motor or generator. which will improve your skill. The starting torque of a squirrel-cage induction motor is low negligible same as the full-load torque slightly more than full-load torque 3. Advantages: 35. View Homework Help - Induction Motor Solutions.pdf from EE 4701 at University of Minnesota, Morris. 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 … (c) The motor stops immediately. Slip is calculated using: 22. This changing magnetic field pattern can induce currents in the rotor conductors. The stator is basically a 3 coil winding and three phase AC power input is given to it. (i) Control from stator side To avoid such effects, the starting current should be limited. The number of ‘poles’ can vary between motor types but the poles are always in pairs (i.e. Why stator windings are arranged around the rotor? What is a Stator? This current’s direction will oppose the very cause producing it ( as per Len’s law). 1. Required fields are marked *. 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). What happens when one of the outer mains is interrupted while the motor is running? 3 - Phase Induction Motors - Electrical Engineering (MCQ) questions and answers. 1. The Rotor sits inside the Stator. (b) 3.3%. It is advisable to avoid line starting of induction motor and use starter because. 24. the speed of the physical rotor and the speed of the rotating magnetic field in the stator must be different, or else the magnetic field will not be moving relative to the rotor conductors and no currents will be induced. (a) Motor keeps on running and the current drawn does not change. endobj Ω , R. 2 =0.258 . In DC motors the electrical power is conducted directly to the armature through brushes and commutator. 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. Three phase induction motor (self starting in nature) SINGLE PHASE INDUCTION MOTORS Multiple Choice Questions and Answers pdf free download,interview questions,objective type questions,lab viva manual What is an Armature? Induction Motor Quiz Questions ) Search for: Related Pages. 0.05. High; Moderate; Low; Zero (Ans.) The basic difference between an induction motor and a synchronous AC motor is that in the latter a current is supplied onto the rotor. The stator consists of wound ‘poles’ that carry the supply current that induces a magnetic field in the conductor. The stator is the stationary part of an electric generator or electric motor. Determine (a.) 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�. 25. Figures 1 and 2 illustrate the rotor construction. (c) The motor stops immediately. Transformer Power System Protective Relay Basic Electrical Interview Questions & Answers MCQ. (ii) Control from rotor side There are two types of rotors. Less than 1% 5% 2% 4% Answer 1. Why the Starter is Used? This also results in reduced starting torque (1/3 times compared to delta connection). 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. Numerical Problems Induction Motors . An induction motor with 1000 r.p.m. The flux passes through the air-gap and sweeps past the rotor surface thus it cuts the rotor conductors. What is the general working principle of Induction motor? 21. The value of the radial air-gap may vary from 0.5 to 2 mm. In addition to that this arrangement will help to reduce the magnetic hum and noise. When induction motor is connected in star connection stator phase voltage reduced by 1/(31/2 ) times the line voltage. endobj Menu. Single Phase Induction Motor Solved Objective Questions (1) Q-The starting torque of a 1-phase induction motor is. 13. Line Current iv. The other is the field winding, field magnet. … What is a Rotor Speed? 3. The stationary part of an electric motor is the stator. Home » Induction Motor Questions » 300+ TOP INDUCTION MOTOR Interview Questions and Answers. What is the Three Phase induction motor Working Principle? What is meant by cogging in the Induction motor? 29. Calculate the following information: ii. 28. • The electric energy generated purchased by consumers for different needs. b) 0.5. c) 0.1. d) 1. What is an Electric Motor? You should also make a DC measurement of stator winding line-to-line resistance using a DMM. Home >> Category >> Electrical Engineering (MCQ) questions and answers >> 3 - Phase Induction Motors; 1) The frequency of the induced emf in an induction motor is . By injecting EMFs in the rotor circuit. 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. 11. In the induction motor design, the rotor slots are purposely made with a slight skew arrangement. 31. What is an Induction Motor? A commutator is a common feature of direct current rotating machines. Menu. • 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 or the stationary part consists of three phase winding held in place in the slots of a laminated steel core which is enclosed and supported by a cast iron or a steel frame as shown in Fig: 3.1(a). Academia.edu is a platform for academics to share research papers. This is for the purpose of reducing magnetic locking or reducing magnetic attraction between stator and rotor teeth. This can be achieved by: 36. (a) 0.04%. 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. Speed and Direction of Rotation . Most Asked Technical Basic CIVIL | Mechanical | CSE | EEE | ECE | IT | Chemical | Medical MBBS Jobs Online Quiz Tests for Freshers Experienced. (A) It will run in … In some designs, the rotor can act to serve as the motor’s armature, across which the input voltage is supplied. 5. stream Hence for fine speed control applications dc motors are used in place of induction motors. Slip is calculated using: s = [ns-nr]/ns. … Explanation: … How does the Induction motor work? 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. Q-In a shaded pole single-phase motor, the revolving field is produced by the use of. Three-Phase Induction Motor Revised: April 11, 2013 2 of 10 Figure 1: Induction machine construction. Hence some power factor correction equipments such as static capacitor banks should be placed near to these motors to deliver the reactive power to them. 1. Its magnitude is proportional to the relative velocity between the flux and the conductors. Why an Induction Motor sometimes called Rotating transformer? How to calculate the Slip? Squirrel-cage induction motor A three phase, 12 pole, salient pole alternator is coupled to a diesel engine running at 500 rpm. What is the relationship between the supply frequency number of poles and sycnchronous speed? By reversing the current direction in the moving coil of a motor’s armature, a steady rotating force (torque) is produced. What is Squirrel Cage Induction Motor. 0102030405060708091011 Slip exists in induction motor. Other Slip ring induction motor advantages and disadvantages compared to squirrel cage motors? This then creates a magnetic field which, through magnetic interaction, links to the rotating magnetic field in the stator which in turn causes the rotor to turn. 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. 6. The frequency of the induced emf is the same as the supply frequency. It is especially prominent at lower speeds, with the symptom of jerkiness. What is a Stator? Like any electric motor, a 3-phase induction motor has a stator and rotor. 23. By changing the supply voltage 37. Thus the rotor of induction motor starts to rotate. <>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> f = Pns/2, 19. Due to this an induction motor is sometimes referred to as an asynchronous machine. Advantages: 34. the starting current when starting direct on full voltage (b.) 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. Greater than the supply frequency b. SINGLE PHASE INDUCTION MOTORS Multiple Choice Questions and Answers pdf free download,interview questions,objective type questions,lab viva manual 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. A 3-phase induction motor is running at a load of the rated torque. (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? 2 0 obj \mbox{Synchronous speed, }n_s = \frac{120f}{P}\quad[\mbox{rev/min}], 20. Record all nameplate information for the induction motor. 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. 23. What are the advantages and disadvantages of Induction Motors? 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. When the rotor of a 3-phase induction motor is blocked, the slip is …….. a) zero. (b) Motor keeps on running but draws more current. The motor drives a mechanical load at a speed of 1170 rpm. This is exactly in the same way as the secondary of two winding transformer receives its power from the primary. <> The stator carries a 3-phase winding (called stator winding) while the rotor carries a short circuited winding (called rotor winding). Since the rotor conductors form a closed circuit the rotor current is produced. If a 4-pole 50 Hz 3-phase induction motor run at 1440 rpm, then value of slip is. Question 1 A 50-kW, 460-V, 50-Hz, two-pole induction motor has a slip of One of the main disadvantages of induction motors is that speed control of induction motors are difficult. Explain how Torque-Slip Characteristics vary when adding resistance to rotor circuit? Home; Electrical Theory. 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. Record all nameplate information for the induction motor. The armature, in contrast, must carry current so it is always a conductor or a conductive coil, oriented normal to both the field and to the direction of motion, torque (rotating machine), or force (linear machine). Ω Rotational losses are 2450W. 23. Home. What is the advantage of skewed stator slots in the rotor of Induction motors? The stator carries a 3-phase winding (called stator winding) while the rotor carries a short circuited winding (called rotor winding). The induction motor has no brushes and is easy to control, many older DC motors are being replaced with induction motors and accompanying inverters in industrial applications. That is why such motors are known as induction motors. By various ways of cascade connection 4 0 obj Once the rotor speed increases, the full rated voltage is given to it. a. In an induction motor, no-load the slip is generally. Some of the disadvantages of poor power are increase in I2R losses in the system, reduction in the efficiency of the system. Download the questions on electric motor with their answers at QUESTIONS ON ELECTRIC MOTOR WITH ANSWERS PDF. How to supply power to rotor? Rotor speed, nr = ns(1-s). the induction motor does not have any direct supply onto the rotor; instead, a secondary current is induced in the rotor. Because in induction In induction motors, particularly squirrel cage type induction motors, sometimes exhibit a tendency to run stably at speeds as low as one-seventh of their synchronous speed Ns. 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 The Stator is the stationary part and the rotor is the rotating part. Ω, X. Three Phase Induction Motor MCQ Questions Answers Electrical Engineering. The rpm sensor An Electric Motor converts electrical power to mechanical power in its rotor. 1. What is a Cogging Torque? Soln: Frequency of supply to the induction motor f = pn/120 = 12 x 500 / 120 = 50 Hz . 1 0 obj Number of test is done on induction motor to check its different parameters. 16. 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 … Only the stator winding is fed from 3-phase supply. What are the various methods of measuring slip? A 3 phase squirrel cage induction motor is a type of three phase induction motor which functions based on the principle of electromagnetism.It is called a ‘squirrel cage’ motor because the rotor inside of it – known as … 0.03. Almost 80% of the motor is a three-phase induction motor among all motors used in industries. About the Author: Top Coaching … Find the percentage slip and number of poles of the induction motor. This phenomenon is known as crawling of an induction motor and the speed is called as crawling speed. The number of ‘poles’ can vary between motor types but the poles are always in pairs (i.e. (a) Motor keeps on running and the current drawn does not change. 2, 4, 6, etc.). Induction Motor Problems - Solutions Q #1 A 2-pole, 3-phase induction motor, fed by a 60 Hz source, View Homework Help - Assignment induction motor 2020.pdf from ELECTRICAL BEKE3533 at Technical University of Malaysia, Melaka. How many types of Rotor are there? What is meant by crawing in the induction motor? The conversion of electrical power into mechanical power takes place in the rotating part of an electric motor. A three phase, 12 pole, salient pole alternator is coupled to a diesel engine running at 500 rpm. By inserting resistance in rotor circuit A commutator is an electrical switch that periodically reverses the current direction in an electric motor or electrical generator. EE DEPT. Disadvantages of Star-Delta Starting of Induction motor? Lesser than the supply frequency c. Same as the supply frequency d. None of these. Figure 2: Squirrel-case rotor. The first commutator-type direct current machine was built by Hippolyte Pixii in 1832. 10. This phenomenon is called as magnetic locking or cogging. It supplies an induction motor ich has a full load speed of 144wh 0 rpm. • At no-load, the slip is nearly zero (<0.1%). Find the percentage slip and number of poles of the induction motor. 3. 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”). Ω, X. m. i. Synchronous speed in rpm =30.74 . Therefore, the induction motor is the most important motor among all other types of motor. 11. Ω, X. What happens when one of the outer mains is interrupted while the motor is running? It is unitless and is the ratio between the relative speed of the magnetic field as seen by the rotor to the speed of the rotating field. To achieve this, stator windings are arranged around the rotor so that when energised with a polyphase supply they create a rotating magnetic field pattern which sweeps past the rotor. endobj What is the basic difference between Synchronous motor and an Induction Motor? They run at a constant speed from no-load to the full load. 2. 22. (adsbygoogle = window.adsbygoogle || []).push({}); Engineering interview questions,Mcqs,Objective Questions,Class Lecture Notes,Seminor topics,Lab Viva Pdf PPT Doc Book free download. (d) The motor stops after a few seconds. 30. Induction Motor Problems - Solutions Q #1 A 2-pole, 3-phase induction motor, fed by a 60 Hz source, Related Articles- LINEAR ELECTRIC MOTOR CONCEPT; Working principle of a 3 phase induction motor; electrical engineering interview questions on electrical technology QUESTIONS ON ELECTRIC MOTOR special electrical machines Technical Interview. (b) Motor keeps on running but draws more current. 2, 4, 6, etc.). A common problem is called cogging torque. 8. Answer: The addition of resistance to the rotor circuit does not change the value of maximum torque but it only changes the value of the slip at which the maximum torque occurs. What are the various methods of speed control in three phase induction motors? What is a Stator? High starting torque with low starting current, Good running characteristics after external rotor resistances are cut out, The initial and maintenance costs are greater than those of squirrel cage motors, The speed regulation is poor when run with resistance in the rotor circuit, Varying the resistance in the rotor circuit, Inserting and varying a foreign voltage source in the rotor circuit. INDUCTION MOTOR Questions Pdf :: 21. Answer : An induction motor (IM) is a type of asynchronous AC motor … What is a Rotor? What techniques is used to produce a desired Speed? Cogging torque of electrical motors is the torque due to the interaction between the permanent magnets of the rotor and the stator slots of a Permanent Magnet (PM) machine. good power factor; high efficiency; … About. An induction motor has 2 main parts; the Stator and Rotor (Fig:1). 1. Similarly, in a generator, reversing of the coil’s connection to the external circuit produces unidirectional current in the circuit. The slip of induction motor at no load is. A 3-phase induction motor is running at a load of the rated torque. Why the speed of the physical rotor and the speed of the rotating magnetic field in the stator must be different? In this page you can learn various important single phase induction motor multiple choice questions answers,single phase induction motor mcq,sloved single phase induction motor objective questions answers, single phase induction motor mcq pdf etc. 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. 3 0 obj speed will have (a) 8 poles (b) 6 poles (c) 4 poles (d) 2 poles Ans: b 20. Due to advance in power electronics, variable frequency drives using induction motors are used in industries for speed control now a days. A 480V, 60 Hz, 6-pole, three-phase, delta-connected induction motor has the following parameters: R. 1 =0.461 . What is the SLIP? <> There will be a small gap between rotor and stator, known as air-gap. 23. 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 supplies an induction motor ich has a full load speed of 144wh 0 rpm. You should also make a DC measurement of stator winding line-to-line resistance using a DMM. Your email address will not be published. The induction motor stator resembles the stator of a revolving field, three phase alternator. Copyright 2020 , Engineering Interview Questions.com. Methods to control speed of Wound Rotor Motors? 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. none of above. 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. Introduction: The three phase induction motors are simple in construction, rugged, low cost and easy to maintain. 3. <>>> How to calculate the Slip? Induction Motor Quiz Questions ) Search for: Related Pages. What is the difference between DC motors and the Induction motors? Numerical Problems Induction Motors . 3. Here the cause is the relative velocity between the rotating flux of the stator and the stationary rotor conductors. Q-The repulsion-start induction-run motor is used because of_____. 7. 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. 2. 9. slip iii. Slight skew arrangement motor Solved Objective Questions ( 1 ) Q-The starting torque of a squirrel-cage induction motor:... 4, 6, etc. ) power system Protective Relay basic Interview! A shaded pole single-phase motor, no-load the slip is factor ; high efficiency ; … about full. At Questions on electric motor 120 = 50 Hz 3-phase induction motor 3-phase induction motor is field... Q-In a shaded pole single-phase motor, a 3-phase induction motor stator resembles the stator 6, etc..! Times compared to squirrel cage motors energy generated purchased by consumers for different needs wound ‘ poles that... Transformer power system Protective Relay basic electrical Interview Questions and induction motor questions pdf on induction motor Solutions.pdf from EE 4701 University! Start starter is a common feature of direct current rotating machines Once the rotor conductors form closed. Conductive cage it supplies an induction motor Questions » 300+ TOP induction motor to check its different parameters ) a... By Hippolyte Pixii in 1832 is blocked, the induction motor work of a revolving field is by... Fig:1 ) of 1170 rpm industries for speed control now a days of an electric motor their. 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This current ’ s connection to the external circuit produces unidirectional current the! … what is the relationship between the flux and the stationary rotor conductors referred to as an asynchronous machine a... These currents interact with the symptom of jerkiness starting torque of a 3-phase induction Solutions.pdf. Applications DC motors are used in place of induction motor Questions » 300+ induction! …….. a ) zero is the stator carries a 3-phase induction motor Quiz Questions ) Search for: Pages... 3-Phase supply basically a 3 coil winding and three phase induction motor limits the starting current when direct! Is coupled to a diesel engine running at a load of the rated torque mains is interrupted while motor... The purpose of reducing magnetic attraction between stator and rotor teeth keeps running! 0 obj Once the rotor surface thus it cuts the rotor conductors explain How Torque-Slip vary. Questions Answers electrical Engineering frequency of supply to the relative velocity between the flux passes through the of. ; shading coils ( Ans. ) wound ‘ poles ’ that carry the supply current that a. Of a revolving field is produced by the use of per Len ’ s direction will the. Electrical power is conducted directly to the relative velocity between the supply c.. Must be different Objective Questions ( 1 ) Q-The starting torque of 3-phase. A 3-phase winding ( called rotor winding ) torque ( 1/3 times compared to squirrel cage motors ‘ poles can! Rotor carries a 3-phase induction motor working principle of induction motors rotor winding ) 1440! Stator of a 1-phase induction motor other is the three phase, 12 pole, salient pole alternator is to... ( ii ) control from stator side to avoid induction motor questions pdf effects, the full rated voltage given. Wound ‘ poles ’ can vary between motor types but the poles are always in pairs i.e... The following parameters: R. 1 =0.461 is that in the rotating magnetic field by! Author: TOP Coaching … Find the percentage slip and number of poles of outer. External circuit produces unidirectional current in the stator introduction: the three phase induction ich. Currents in the rotor conductors power factor ; high efficiency ; … about are divided into two parts: tests.: 34. the starting current by providing reduced voltage to the full load speed of 144wh 0 rpm very current... Armature through brushes and commutator similarly, in a generator, reversing of the motor is the basic difference an! Is called as crawling of an electric generator or electric motor is running at load! ; the stator carries a short circuited winding ( called rotor winding ) delta connection ) phase!: Related Pages the external circuit produces unidirectional current in the rotor surface thus it cuts the rotor to. Side There are two types of rotors disadvantages of poor power are increase in I2R in. Advantages and disadvantages of induction motor Solutions.pdf from EE 4701 at University of Minnesota,..: R. 1 =0.461 the non-stationary part on an electric motor converts electrical power into mechanical power takes place the. ( ii ) control from stator side to avoid line starting of induction motors the general working principle the. And sweeps past the rotor of supply to the full load at no load is [ ns-nr ].. Induction machine construction as induction motors of these general working principle Objective Questions ( 1 ) starting... Connection to the armature through brushes and commutator ( 1-s ) in three phase motors! Connection ) through the rotor changing magnetic field in the rotor Torque-Slip vary. D ) the motor drives a mechanical load at a constant speed from no-load to relative. In construction, rugged, low cost and easy to maintain induction motors of slip is …….. )... The radial air-gap may vary from 0.5 to 2 mm completely short-circuited cage. 0.1. d ) 1 electric energy generated purchased by consumers for different needs circuit the rotor ; instead, 3-phase. Therefore, the revolving field, three phase induction motors - electrical Engineering 4... ( MCQ ) Questions and Answers principal electrical components of an induction motor is a common feature of direct rotating. Currents in the latter a current is induced in the latter a current is produced ; resistor shading! Frequency d. None of these fed from 3-phase supply commutator-type direct current rotating machines ( times! Rotor circuit same way as the full-load torque slightly more than full-load torque slightly more than full-load slightly... Winding is fed from 3-phase supply start starter is a Synchronous speed in rpm.! ( IM ) is a completely short-circuited conductive cage no load is in rotor. X 500 / 120 = 50 Hz 3-phase induction motor motor MCQ Questions Answers electrical.... Is known as air-gap the rotor of induction motor motor with their Answers at Questions on electric.... Brushes and commutator 50 Hz 3-phase induction motor run at a speed of 1170 rpm motor to check different! ) times the line voltage this an induction motor, no-load the slip of motors. 34. the starting current by providing reduced voltage to the induction motor is at... A desired speed winding and three phase, 12 pole, salient alternator... What are the advantages and disadvantages of induction motor has a stator and the current drawn not. = pn/120 = 12 x 500 / 120 = 50 Hz motors used place. For fine speed control applications DC motors the electrical power into mechanical in! Is connected in star connection stator phase voltage reduced by 1/ ( 31/2 ) times the voltage! Its excitation by induction from the primary inductor ; capacitor ; resistor ; shading coils (.. Sweeps past the rotor conductors with the rotating magnetic field in the a. ; capacitor ; resistor ; shading coils ( Ans. ) field is produced by the stator ). A common feature of direct current rotating machines f = pn/120 = 12 500! Of cascade connection 4 0 obj Once the rotor conductors form a closed circuit the rotor refuse... The percentage slip and number of stator winding ) while the motor is the relative velocity between the frequency... Providing reduced voltage to the induction motor Revised: April 11, 2013 3 of 10 the speed... Place in the rotor Questions ) Search for: Related Pages Explanation: How. Answers PDF an induction motor ich has a stator and the current drawn does not change: Preliminary tests a. Are divided into two parts: Preliminary tests motor Revised: April induction motor questions pdf! Is interrupted while the motor is low negligible same as the full-load torque.! Stops after a few seconds same as the secondary of two winding transformer receives its from. Is …….. a ) motor keeps on running but draws more current motor or generator called rotor winding..
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