Do AC induction motors have back EMF?

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asked Mar 15, 2018 by anonymous

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asked Mar 20, 2018 by anonymous

In case of D.C. shunt motors the speed is dependent on back e.m.f. only because?

Last answer: In case of D.C. shunt motors the speed is dependent on back e.m.f. only because flux is practically constant in D:C. shunt motors.

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145 views 1 answer

asked Apr 27, 2020 by anonymous

What is back emf?

Last answer: Back EMF: When a current carrying conductor is placed in a magnetic field it experiences a force; when it moves due to the force it (conductor) cuts the magnetic field due to which an emf is ... (hence the applied armature voltage) is opposed by the induced emf which is therefore called as Back emf.

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61 views 1 answer

asked Mar 15, 2018 by anonymous

What is back EMF of synchronous motor?

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asked Mar 15, 2018 by anonymous

What is back EMF in inductor?

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126 views 0 answers

asked Mar 15, 2018 by anonymous

What is the back EMF in Transformers?

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59 views 0 answers

asked Mar 15, 2018 by anonymous

What is the back EMF of a dc motor?

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2.5k views 0 answers

asked Mar 15, 2018 by anonymous

What is the back EMF of the motor?

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asked Mar 15, 2018 by anonymous

What is the back EMF?

Last answer: When the armature of a d.c. motor rotates under the influence of the driving torque, the armature conductors move through the magnetic field and hence e.m.f. is induced in them as in a generator. The ... that energy conversion in a d.c. motor is only possible due to the production of back emf.

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66 views 1 answer

asked Mar 18, 2018 by anonymous

The back emf of synchronous motor depends on?

Last answer: The back emf of synchronous motor depends on load angle.

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47 views 1 answer

asked Mar 20, 2018 by anonymous

The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is?

Last answer: The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is 0.5.

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144 views 1 answer

asked Mar 20, 2018 by anonymous

What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?

Last answer: The armature may burn if the back e.m.f. of a D.C. motor vanishes suddenly.

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374 views 1 answer

asked Sep 3, 2019 by anonymous

Why are DC motors used in trains and not AC motors ?

Last answer: The reason is torque. torque is inversely proportional to speed..i.e when th knowe train comes to rest position to motion.. initial speed is zero..so it requires high starting torque for ... current will flow through field and armature coils then maximum torque is available at the intial condition.

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138 views 1 answer

asked Apr 29, 2018 by anonymous

Which of the following motors can run on both AC and DC?

Which of the following motors can run on both AC and DC? A) Universal motor B) Dual wattage motor C) Flexible motor D) All the above

Last answer: Which of the following motors can run on both AC and DC? A) Universal motor B) Dual wattage motor C) Flexible motor D) All the above

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113 views 1 answer

asked Apr 28, 2018 by anonymous

Slot harmonics are reduced in induction motors by using

Slot harmonics are reduced in induction motors by using (A) fractional-pitch windings (B) fractional-slot windings (C) integral-slot windings (D) distributed windings

Last answer: Slot harmonics are reduced in induction motors by using fractional-slot windings

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61 views 1 answer

asked Apr 28, 2018 by anonymous

Generally, Crawling in squirrel cage induction motors is tendency to run stably at speeds as low as

Generally, Crawling in squirrel cage induction motors is tendency to run stably at speeds as low as (A) One-third of their synchronous speed (B) One-fifth of their synchronous speed (C) One-seventh of their synchronous speed (D) One-ninth of their synchronous speed

Last answer: Generally, Crawling in squirrel cage induction motors is tendency to run stably at speeds as low as One-seventh of their synchronous speed

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77 views 1 answer

asked Sep 9, 2017 by anonymous

is induction motor ac or dc?

Last answer: Induction motor is a AC motor it is also known as asynchronous motor .

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73 views 1 answer

asked Mar 20, 2018 by anonymous

The capacitors used in single-phase capacitor motors have no?

Last answer: The capacitors used in single-phase capacitor motors have no polarity marking.

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105 views 1 answer

asked Mar 20, 2018 by anonymous

Most of the fractional horsepower motors have either?

Last answer: Most of the fractional horsepower motors have either plain or sleeve bearings.

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59 views 1 answer

asked Aug 17, 2019 by anonymous

Self induced emf and Mutually induced emf

Last answer: (i) Self-induced e.m.f.: The e.m.f. induced in a coil due to the change of its own flux linked with it, is called self-induced e.m.f. (ii) Mutually induced e.m.f.: The e.m.f. induced in a coil due to the changing current in the neighbouring coil, is called mutually induced e.m.f.

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38 views 1 answer

asked Sep 7, 2018 by anonymous

What is Phase sequence? Draw waveforms of 3 phase emf.

Last answer: Phase sequence: It is the order in which the three phases reach their peak or maximum values. It is shown in below fig. the phase sequence is A-B-C (or R-Y-B). In the following waveforms, it is ... 120º, B- phase voltage attains its positive maximum value. So the phase sequence is R-Y-B.

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67 views 1 answer

asked Sep 4, 2018 by anonymous

Compare statically induced emf with dynamically induced emf on any four points.

Last answer: Statically induced emf Dynamically induced emf Emf is induced without any relative motion between conductor and magnetic field. Emf is induced due to relative motion between conductor ... induced in transformer windings e.g emf induced in Generator, Alternator armature windings

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113 views 2 answers

asked Aug 8, 2018 by anonymous

Explain the term self induced EMF with a neat diagram.

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asked Aug 8, 2018 by anonymous

Define: 1) statically induced EMF 2) dynamically induced EMF

Define: 1) statically induced EMF 2) dynamically induced EMF Write the names of equipments in which these two types of EMF get induced

Last answer: Concept of statically induced emf: The emf induced in coil or conductors without any relative motion between it and magnetic field is called statically induced emf. When conductor is stationary and flux ... it. This emf is dynamically induced emf. e.g. Emf induced in generators, alternator.

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370 views 3 answers

asked Aug 8, 2018 by anonymous

List the two types of induced EMF.

Last answer: There are two types of EMF one is statically induced EMF and second is dynamically induced EMF.

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71 views 1 answer

asked Mar 14, 2018 by anonymous

Do cell phones use AC or DC current?

Last answer: DC of course.

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177 views 2 answers

asked Mar 11, 2018 by anonymous

Why do we use AC current in our homes?

Last answer: We used it for cooking rice, For washing clothes and for lights in the house.

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174 views 3 answers

asked Mar 15, 2018 by anonymous

Why does induction motor have high starting current?

Last answer: In induction motor , the flux produce is quadrature to the applied voltage. Since when we are going to start motor , there is no flux present inside . So in order to lets say compensate it ... times of current to further increase flux. So that is reason for high starting current in induction motor

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115 views 2 answers

asked Apr 27, 2020 by anonymous

Explain dynamic and static induced emf with neat diagram.

Last answer: Dynamically Induced EMF:- In this case, either coil moves or magnet moves, so that there is relative motion between coil & magnetic field. Thus magnetic field is cut by coil & emf is induced in it. The emf ... The expression for induced EMF is e= -L(di/dt) or = -N(dϕ/dt).

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93 views 1 answer

asked Dec 13, 2019 by UMESH y

Emf definition

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asked Apr 29, 2018 by anonymous

The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors

The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is (1) 1000V (2) 100V (3) 600V (4) 10,000V

Last answer: The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is 1000V

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161 views 1 answer

asked Apr 28, 2018 by anonymous

The fractional-pitch used for eliminating 7th harmonic from the emf wave of an alternator is

The fractional-pitch used for eliminating 7th harmonic from the emf wave of an alternator is (A) 2/3 (B) 5/6 (C) 7/8 (D) 6/7

Last answer: The fractional-pitch used for eliminating 7th harmonic from the emf wave of an alternator is 6/7

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289 views 1 answer

asked Dec 22, 2017 by anonymous

What is the EMF equation of the transformer?

Last answer: E1 =2(3.142)fN1 (flux)1E2 =2(3.142)fN2(flux)2

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123 views 1 answer

asked Aug 17, 2019 by anonymous

Suggest electric motors for i) traction ii) crane iii) lathe machine iv) domestic fan.

Last answer: i) Traction :- DC Series motor ii) Crane :- DC Series motor iii) Lathe machine :- 3 phase Induction motor or DC shunt motor iv) Domestic fan :- 1 phase induction motor

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36 views 1 answer

asked Aug 17, 2019 by anonymous

State which electric motors are generally used in electro agro systems with reason.

Last answer: 1) 3 phase induction motor is used in electro agro system for water pumping from wells as 3 phase ac supply is easily available, cost of induction motor is less, maintenance free being rugged ... as 1 phase ac supply is easily available for domestic purpose, repair is simple and easily available.

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66 views 1 answer

asked Aug 17, 2019 by anonymous

State factors for selection of motors as drive.

Last answer: Following Factors governing / or are considered while selecting electric drive (Motor) for particular application: Factors to be considered for selection of Electrical Drives: 1) Nature of Supply:- ... level, load equalization 7) Cost: - Capital, Running and maintenance cost should be less.

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1.2k views 2 answers

asked Jul 30, 2019 by anonymous

Compare variable reluctance and permanent magnet motors.

Last answer: Variable reluctance Motor Permanent magnet motors The rotor is not magnetised The rotor is magnetised High torque to inertia ratio Low torque to inertia ratio ... rotor has salient pole construction The rotor has mostly smooth cylindrical type of construction.

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2.4k views 1 answer

asked Jul 30, 2019 by anonymous

What are the factors to be considered while selection of motors for different drives?

Last answer: Following Factors are considered while selecting electric drive (Motor) for particular application: Factors to be considered for selection of Electrical Drives: 1) Nature of Supply:- Whether supply ... , load equalization 7) Cost: - Capital, Running and maintenance cost should be less.

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66 views 1 answer

asked Jul 24, 2019 by ZAHID

3 phase motor 42 hp same ratting two motors but pole change 2 and 4 pole tell me difference amp of both motors

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2.5k views 0 answers

asked Mar 11, 2018 by anonymous

How do induction heaters work?

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31 views 0 answers

asked Mar 18, 2018 by anonymous

Which motor have more efficiency, synchronous motor or induction motor?

Last answer: Synchronous motor has more efficiency.

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61 views 1 answer

asked May 8, 2018 by anonymous

A relay used for protection of motors against overload is :

A relay used for protection of motors against overload is : (A) Impedance relay (B) Electromagnetic attraction type (C) Thermal relay (D) Buchholz's relay

Last answer: A relay used for protection of motors against overload is : Thermal relay

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232 views 1 answer

asked Apr 29, 2018 by anonymous

Damper winding is provided in 3 phase synchronous motors to :

Last answer: Damper winding is provided in 3 phase synchronous motors to : provide starting torque and prevent hunting

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69 views 1 answer

asked Apr 29, 2018 by anonymous

Stepper motors are used in

Stepper motors are used in (1) printers (2) lifts (3) amplifiers (4) oscillators

Last answer: Stepper motors are used in printers

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46 views 1 answer

asked Apr 28, 2018 by anonymous

Which of the following test is usually conducted to determine the efficiency of traction motors ?

Which of the following test is usually conducted to determine the efficiency of traction motors ? (A) Field’s test (B) Swinburne’s test (C) Hopkinson’s test (D) Retardation test.

Last answer: Which of the following test is usually conducted to determine the efficiency of traction motors ? (A) Field’s test (B) Swinburne’s test (C) Hopkinson’s test (D) Retardation test.

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205 views 1 answer

asked Apr 26, 2018 by anonymous

Which of the following motors is being extensively used in servo applications ?

Which of the following motors is being extensively used in servo applications ? A. AC motor B. Field controlled dc motor C. Armature controlled dc motor D. None of these

Last answer: Which of the following motors is being extensively used in servo applications ? A. AC motor B. Field controlled dc motor C. Armature controlled dc motor D. None of these

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146 views 1 answer

asked Mar 20, 2018 by anonymous

During rheostat braking of D.C. series motors?

Last answer: During rheostat braking of D.C. series motors motor is run as a generator.

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62 views 1 answer

asked Mar 20, 2018 by anonymous

D.C. shunt motors are used for driving?

Last answer: D.C. shunt motors are used for driving machine tools.

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68 views 1 answer

asked Mar 20, 2018 by anonymous

Why are the D.C. motors preferred for traction applications?

Last answer: The D.C. motors preferred for traction applications beacuse the speed is inversely proportional to the torque and the torque is proportional to square of armature current.

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96 views 1 answer

asked Mar 20, 2018 by anonymous

In case of conductively compensated D.C. series motors, the compensating winding is provided?

Last answer: In case of conductively compensated D.C. series motors, the compensating winding is provided in series with armature winding.

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71 views 1 answer

asked Mar 20, 2018 by anonymous

A direct online starter is used for starting motors?

Last answer: A direct online starter is used for starting motors up to 5 H.P.

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59 views 1 answer

Do AC induction motors have back EMF?

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