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What is the principle of DC generator?

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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 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is

Answer : A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is 0.87

Description : The fall in speed of a dc generator due to increase in load can be corrected by  (1) cooling the armature.. (2) increasing the excitation. (3) reducing the load voltage. (4) increasing the input to the prime mover

Answer : It   can  be  corrected  by  increasing  the  input  to  the  prime  mover.

Description : In a DC generator the windings of interpoles are connected :  (A) in series with main field winding, to create a pole,of same polarity as the main pole ahead in the direction of rotation.  ... winding, to create a pole of opposite polarity as the main pole ahead in the direction of rotation.

Answer : In a DC generator the windings of interpoles are connected :  in series with the armature winding, to create a pole of same polarity as the main pole ahead in the direction of rotation. 

Description : From which material field coils of DC generator are made of?

Answer : Field coils of DC generator are usually made of copper.

Description : Why is the armature of DC generator laminated?

Answer : The armature of DC generator is laminated to reduce eddy current losses.

Description : What is the principle of DC motor?

Description : State the function of commutator in DC generator and name the material used for commutator.

Answer : Function of Commutator: Commutator converts AC induced in armature winding into DC for external load. Material: i) Commutator segments are made up of Copper. ii) Commutator segments are insulated from each other by Mica.

Description : The eddy current loss in a dc generator is 400 W at 40 Hz frequency of reversal and constant flux density. When frequency is increased to 50 Hz., eddy current loss is :  (A) 256 W (B) 320 W (C) 500 W (D) 625 W

Answer : The eddy current loss in a dc generator is 400 W at 40 Hz frequency of reversal and constant flux density. When frequency is increased to 50 Hz., eddy current loss is : 625 W

Description : The terminal characteristics of a dc generator suitable for electric welders is (A) separately excited generator (B) shunt generator (C) series generator (D) differentially compounded generator

Answer : The terminal characteristics of a dc generator suitable for electric welders is differentially compounded generator

Answer : The critical resistance of the D.C. generator is the resistance of field.

Description : If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be?

Answer : If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be zero.

Answer : A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be about 2 V.

Answer : In a level compounded D.C. generator, full load terminal voltage is equal to no-load terminal voltage.

Answer : In a D.C. generator in case the resistance of the field winding is increased, then output voltage will decrease.

Answer : A D.C. generator can be considered as rotating amplifier.

Answer : In a D.C. generator, the critical resistance refers to the resistance of field.

Answer : Flashing the field of D.C. generator means creating residual magnetism by a D.C. source.

Answer : If a D.C. generator fails to build up the probable cause could not be field resistance less than the critical resistance.

Answer : In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when there is no load on|he generator.

Answer : The e.m.f. generated in a D.C. generator is directly proportional to speed of armature.

Answer : In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when number of poles is 2.

Answer : D.C. generator generally preferred for charging automobile batteries is long shunt compound generator.

Answer : The armature core of a D.C. generator is usually made of silicon steel.

Answer : In a D.C. generator the ripples in the direct e.m.f. generated are reduced by using carbon brushes of superior quality.

Answer : Magnetic field in a D.C. generator is produced by electromagnets.

Answer : The demagnetising component of armature reaction in a D.C. generator reduces generator e.m.f.

Answer : If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be crossmagnetisation as well as demagnetising.

Answer : In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be 8.

Description : For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f. ?

Answer : Wave winding

Answer : In a D.C. generator, the iron losses mainly take place in armature rotor.

Answer : The condition for maximum efficiency for a D.C. generator is variable losses equal to constant losses.

Answer : The total losses in a well designed D.C. generator of 10 kW will be nearly 500 W.

Description : What is the principle of synchronous motor?

Description : What is the principle of AC motor?

Description : Describe the working principle of photoelectric pickup type tacho-generator.

Answer : Working: Working principle: The light passes through the holes available on the rotating disc with a specific interval, depends on the angular speed of disc having equidistant holes. The frequency of this light pulses ... by N=f/HS  N=speed  f=frequency  Hs=holes on the disc

Description : What is the difference between synchronous and asynchronous generator?

Description : What are the main parts of a generator?

Answer : the main parts of the generator are as follows yoke Armature Poles field winding Prime mover  Commutator Shaft Bearings Brushes

Description : A _________ is used to measure the stator % winding temperature of the generator.  (A) Thermocouple (B) Pyrometer (C) Resistance thermometer (D) Thermometer

Answer : A Resistance thermometer is used to measure the stator % winding temperature of the generator. 

Description : In a synchronous generator if the excitation increased from a low value to normal value, with a fixed load  (A) The armature current increases and the power factor decreases  (B) The armature ... but is lagging  (D) The armature current decreases and the power factor increases and is leading

Answer : In a synchronous generator if the excitation increased from a low value to normal value, with a fixed load The armature current decreases and the power factor increases and is leading

Description : In a synchronous generator delivering lagging power factor load  (1) the excitation emf leads terminal voltage by the power angle (2) the excitation emf lags terminal voltage by the power angle (3) ... by the power factor angle (4) excitation emf lags the terminal voltage by the power factor angle

Answer : In a synchronous generator delivering lagging power factor load the excitation emf leads terminal voltage by the power angle

Description : The armature reaction in a synchronous generator supplying leading power factor load is (A) magnetizing (B) demagnetizing (C) demagnetizing and cross-magnetizing (D) magnetizing and cross-magnetizing

Answer : The armature reaction in a synchronous generator supplying leading power factor load is magnetizing and cross-magnetizing

Answer : if induction motor rotates exceed than its synchronous speed, it acts as a generator.

Answer : In D.C. generators on no-load, the air gap flux distribution in space is flat topped.

Description : What is the working principle of pressure transmitter?

Description : What is the RPM of a DC motor?

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

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

Description : State working principle of alternator. State the meaning self and separate excitation. 

Answer : Working principle of alternator: When a conductor is moved in magnetic field or a magnetic field moved with respect to conductor, according to Faraday's law of electromagnetic induction, the conductor ... like battery or shaft-mounted exciter, then the excitation is said to be separate excitation.

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