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AC motor

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AC motor

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•AC motor have two types one is Induction motor and second is synchronous motor.

•Induction motor have two types one is single phase induction motor and second is three phase induction motor.

•Single phase induction motor is not self starting and three phase induction motor is self starting.

•Based on starting method single phase induction motor is further divided into four types one is Split phase induction motor second is shaded pole induction motor and third is capacitor start induction motor and fourth is capacitor start capacitor run induction motor.

•Three phase induction motor have two types of rotor one is slipring type and second is squirrel cage type.

•Synchronous means rotating magnetic field and rotor rotation speed is same.

•Synchronous motor have both AC and DC supply stator have three phase AC supply and rotor have DC supply.

•Synchronous motor is use for constant speed.

•Synchronous motor have two types of rotor one is salient pole (low speed) and second is non salient pole (high speed) rotor.

•Synchronous motor is use for constant speed motor purpose and it is also use for power factor improvement device (called synchronous condenser).

•Synchronous motor is not self starting motor so using  external motor or we have to start it as induction motor.

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Related questions

Description : What are the parts of AC motor?

Description : What is the principle of AC motor?

Description :

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

Description : State the modification to be done in dc series motor to work satisfactorily as ac series motor. State applications of ac series motor.

Answer : Modifications are necessary in a dc series motor so that it operates satisfactorily on ac supply. The modifications are as follows:  1) AC series motor is built with a few field turns as ... and grinders 5) High speed vacuum cleaners 6) Sewing machines 7) Food processors 8) Drilling machine 

Description : The direction of rotation of an inverter fed 3-phase ac motor is reversed by (A) a mechanical reversing switch (B) reversing the input dc link voltage (C) operating the inverter as a rectifier (D) changing the sequence of switching

Answer : The direction of rotation of an inverter fed 3-phase ac motor is reversed by changing the sequence of switching

Description :

Answer : If a D.C. motor is connected across the A.C. supply it will burn due to heat produced in the field winding by eddy currents.

Description :

Answer : A.C. series motor as compared to D.C. series motor has smaller brush width, less number of field turns, more number of armature turns, less air gap.

Description :

Answer : If a D.C. series motor is operated on A.C. supply, it will spark excessively, have poor efficiency, have poor power factor.

Description :

Answer : In a A.C. series motor armature coils are usually connected to commutator through resistance.

Description :

Answer : In A.C. series motor compensating winding is employed to reduce sparking at the brushes.

Description : What is the difference between an AC and DC generator?

Answer : The generator which generates DC voltage is called DC generator and generator which generates AC voltage is called AC generator (or) Alternator. In DC generator armature is rotated and field winding ... generator. A DC generator can generate low voltages but an AC generator can generate upto 11kv.

Description : A three-phase synchronous motor connected to ac mains is running at full load and unity power factor. lf its shaft load is reduced by half and field current is held constant then its new power factor will be

Answer : Leading

Description :

UNIT 1 fundamentals of AC rotating machine


Contents

1.1 Introduction

1.2 Advantages

1.3 Parts of AC machines

1.4 Synchronous speed

1.5 AC winding

1.6 Winding factor (Coil pitch and distributed winding)

1.7 Distribution factor

1.8 EMF equation of alternator or generator

1.9 Numericals

1.10 Harmonic

1.11 Slot harmonics

1.12 Harmonics minimization

Answer : 1.2 Advantages: In practices most of alternator have rotating magnetic field type construction with stationary armature due to following reason. The generation level of AC voltage may be in the range ... at high speed. Only two Slip rings are required to excited the field by AC supply.

Description : What would happen if a DC motor was supplied with AC ?

Answer : With three phase induction motor, humming and not rotate, but if single phase universal motor like air blower, home mixture, motor run on constant speed..speed variation not possible...

Description :

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

Description :

Answer : Centrifugal switch disconnects the auxiliary winding of the motor at about 70 to 80 percent of synchronous speed.

Description : What is the definition of induction motor?

Answer : its working on magnetic base made by coils and its work with 1 phase or 3 phase ac or dc supply

Description : What is the function of induction motor?

Answer : while you give supply to motor its motor run on magnet base 

Description : What will happen if you increase the current in the motor?

Answer : Increasing current means increasing frequency of the motor because current is directly proportional to rotations of the motor rotor

Description :

What is the principle of synchronous motor?

Description : What is the use of synchronous motor?

Description : What is the RPM of a DC motor?

Description :

What is mean by plugging in three phase induction motor?

Answer : Plugging in three-phase induction motor means interchanging of any two phases of a stator for quick stopping.

Description : What are the speed control methods of dc motor?

Answer : Field control of DC motor Armature control of DC motor

Description : what is the difference between synchronous and asynchronous motor?

Answer : Asynchronous motors and syncrouns motor are called as dc machines.  and also syncrouns motor called as induction motor. Asynonymous motor as are rotates with constant speed we not able to operate . ... It is able to operate. These are a small difference between syncrouns and asynchronous motors. 

Description :

What is the advantage of AC over DC electrical transmission?

Description : What is the conversion between. AC to AC ? DC to DC? AC to DC? DC to AC ?

Answer : 1.ac to ac is regulation 2.dc to dc is chopper 3.ac to dc is rectifier 4.dc to ac is inverter

Description : What is the need of polarity marking in polyphase AC circuits?

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Description : What is the direction of an AC current?

Answer : The magnitude and direction of alternating current is changes with respect to time. So for half cycle it is positive and for next half cycle it is negative.

Description : What is the symbol for AC power?

Answer : If you need to measure alternating current in a circuit, different multimeters have different symbols to measure it (and the corresponding voltage), usually "ACA" and "ACV," or "A" and "V" with a squiggly line (~) next to or above them.

Description : What is the difference between AC and DC drive?

Answer : AC means alternating current It's Frequency is 50hz Dc means direct current ItsI Frequency is 0Hz

Description : What is the use of AC and DC drives?

Description : What is the purpose of a capacitor in an AC circuit?

Answer : Every AC supply is not ideal AC it contains DC component so to provide restriction to DC component in supply we have to use Capacitor

Description :

Split phase induction motor

Answer : Split phase induction motor : There are two windings used in split phase induction motor. It is a type of single-phase induction motor. There are two winding one is called main winding and ... motor have low starting torque it is used for small fans, blowers, centrifugal pumps, grinders etc.

Description :

Describe the reason of using dc series motor for electric trains.

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Answer : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be 474 V

Description : Damper winding in a synchronous motor

Answer : Damper winding in a synchronous motor Serves to start the motor.

Description : In a double squirrel cage induction motor, good starting torque is produced as (A) Large current flows through the outer high resistance winding. (B) Large current flows through the inner high resistance winding. (C) Small current flows through the outer high resistance winding. (D) Large current flows through the inner low resistance winding.

Answer : In a double squirrel cage induction motor, good starting torque is produced as Large current flows through the outer high resistance winding.

Description : A change of 4% in the supply voltage to an induction motor will produce a change of approximately

Answer : A change of 4% in the supply voltage to an induction motor will produce a change of approximately 8% in the rotor torque

Description : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is

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Description : In an induction motor if the flux density is reduced to one-half, of its normal value then the torque will  (1) reduce to one-half (2) reduce to one-fourth (3) remain unchanged (4) increase four times

Answer : In an induction motor if the flux density is reduced.to one-half, of its normal value then the torque will reduce to one-fourth

Description : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque  (1) Decreases (2) Increases (3) Remains constant (4) None of the above

Answer : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque Increases 

Description : The number of poles of 8/6 stepper motor can be :

Answer : The number of poles of 8/6 stepper motor can be : 4

Description : In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is :

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Description : For using regenerative breaking, the most suitable motor is :  (A) DC series motor  (B) Slip ring induction motor  (C) Squirrel cage induction motor  (D) Synchronous motor

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Answer : The slip of 400 V, three phase, 4 -pole induction motor when rotating at 1440 rpm is 4 percent

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Answer : The speed of a 2-pole, 3-phase stepper motor operated by 1200 pulses/min 200 rpm

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