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Answer :

Open circuited armature coil of a D.C. machine is identified by the scarring of the commutator segment to which open circuited coil is connected and indicated by a spark completely around the commutator.

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Answer :

In a D.C. machine stray loss is the sum of iron loss and mechanical loss.

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Answer :

To avoid formation of grooves in the commutator of a D.C. machine the brushes of opposite polarity should track each other.

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Answer :

Iron losses in a D.C. machine are independent of variations in load.

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Answer :

In a four-pole D.C. machine alternate poles are north and south.

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Answer :

In case of D.C. machine winding, number of commutator segments is equal to number of armature coils.

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423 views 1 answer
Description :

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

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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228 views 1 answer
Description :

In a dc machine, interpoles are used to  (1) neutralize the effect of armature reaction in the interpolar region (2) generate more induced emf in the armature (3) avoid interference of the armature flux with the main -field flux (4) reduce the demagnetizing effect of armature reaction

Answer :

In a dc machine, interpoles are used to neutralize the effect of armature reaction in the interpolar region

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Description :

The magnetic neutral plane shifts in a dc machine (A) in the direction of motion of motor (B) in the direction of motion of generator (C) due to increase in the field flux (D) cause reduction of flash over between commutator segments

Answer :

The magnetic neutral plane shifts in a dc machine in the direction of motion of generator

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104 views 1 answer
Description :

Answer :

Copper losses,iron losses,variable losses , constant losees

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159 views 1 answer
Description :

Explain concept of back emf in DC machine. State how it governs armature current. 

Answer :

Back emf: When the armature of DC machine rotates under the influence of driving torque, the armature conductors move in the magnetic field and cut it and hence emf is induced in them. The ... flow of armature current i.e. it automatically changes the armature current to meet load requirements.

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155 views 1 answer
Description :

What is the percentage of stray losses in DC machine?

Answer :

Percentage of stray losses in DC machine is about 1 % .

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Description :

Answer :

Iron loss, copper loss and mechanical losses these are the losses in DC machine.

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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

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Description :

A 36 slot, 4 -pole, dc machine has a simplex lap winding with two conductors per slot. The back pitch and front pitch adopted could be respectively

Answer :

A 36 slot, 4 -pole, dc machine has a simplex lap winding with two conductors per slot. The back pitch and front pitch adopted could be respectively 19,17

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337 views 1 answer
Description :

Aluminium is not used as winding wire for the armature of a dc machine because  (1) aluminium has low resistivity (2) a large winding space is taken by aluminium conductors and creates jointing problems (3) the thermal conductivity of aluminium is low (4) aluminium has low conductivity as compared to copper

Answer :

Aluminium is not used as winding wire for the armature of a dc machine because  (2) a large winding space is taken by aluminium conductors and creates jointing problems (3) the thermal conductivity of aluminium is low (4) aluminium has low conductivity as compared to copper

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Description :

Why poles of dc machine are laminated?

Answer :

Poles of DC machines are laminated to reduce the eddy current losses in the poles.

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Description :

Brushes of DC machine are made up of ?

Answer :

Brushes of DC machine are made up of carbon.

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Description :

Answer :

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

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Description :

Answer :

In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called armature.

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Description :

Answer :

Armature coil is short circuited by brushes when it lies along neutral axis.

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Description :

The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole)  (A) has q -axis current only (B) has d -axis current only (C) has both d and q axis currents (D) cannot be divided between q and d axis currents

Answer :

The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) has d -axis current only

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Description :

Answer :

A synchronous machine with low value of short-circuit ratio has lower stability limit.

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Description :

In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as  (1) synchronous motor (2) synchronous generator (3) asynchronous motor (4) asynchronous generator

Answer :

In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as synchronous generator 

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Description :

Answer :

Eddy currents are induced in the pole shoes of a D.C. machine due to relative rotation between field and armature.

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Description :

Answer :

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

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Description :

Answer :

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

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Description :

Answer :

The wattage of motor for driving domestic sewing machine will be around 100 to 150 W.

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Description :

If we change the excitation of synchronous machine will it affect on power factor?

Answer :

Yes, If we change the excitation of synchronous machine it will affect on power factor. If the synchronous motor is overexcited then it will have leading power factor and if the motor is underexcited then it will have lagging power factor.

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Description :

If we change the excitation of synchronous machine will it affect on motor speed?

Answer :

No, If we change the excitation of synchronous machine it will not affect on motor speed.

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79 views 1 answer
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.

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226 views 1 answer
Description :

Answer :

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

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Description :

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.

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Description :

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.

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Description :

Answer :

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

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Description :

Answer :

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

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Description :

What is fuzzy logic in a washing machine?

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Description :

Define Feed and speed in shaping machine

Answer :

1) Feed: Feed (S) is the relative movement of the work or tool in a direction perpendicular to the axis of reciprocation of the ram per double stroke. It is expressed in mm per stroke. 2) Speed: ... speed is the speed at which the metal is removed by the cutting tool in a period of one minute.

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Description :

function of exposer in photocopier machine.

Answer :

A bright lamp illuminates the original document, and the whitws areas of the original document reflect the light onto the surface of the photoconductive drum. The areas of the drum that are exposed ... discharge to the ground. The areas of the drum not exposed to light remains negatively charged

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Description :

In 8085 microprocessor, how many T-states does OPCODE FETCH machine cycle normally require (i.e., when HOLD and WAIT signals are NOT forced)? A) 4 to 6 B) 3 to 8 C) 2 to 3 D) 8 to 12 

Answer :

In 8085 microprocessor, how many T-states does OPCODE FETCH machine cycle normally require (i.e., when HOLD and WAIT signals are NOT forced)? A) 4 to 6 B) 3 to 8 C) 2 to 3 D) 8 to 12 

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Description :

A cumulatively compounded d.c. generator is supplying 20 A at 200 V. If the series field winding is short circuited, the terminal voltage will (a) remain unaltered (b) rise to 220 V (c) shoot up to a very high value (d) become less than 200 V 

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75 views 0 answers
Description :

Explain the basic parts of a slotting machine with neat sketch. 

Answer :

Base or Bed The base is rigidly built to take up all the cutting forces and the entire load of the machine. The top of the bed is accurately finished to provide guideways on which ... return mechanism. 2. Variable speed reversible motor drive mechanism. 3. Hydraulic drive mechanism.

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Description :

Write down the basic parts of a lathe machine with their proper functions. 

Answer :

Important Parts of Lathe and their Functions 1. Bed It is the main body of the machine. All main components are bolted on it. It is usually made by cast iron due to its high compressive strength and ... carriage on bed. 12. Spindle: It is the main part of lathe which holds and rotates the chuck.

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Description :

The 'Equal area criterion' for the determination of transient stability of a synchronous machine connected to an infinite bus  (1) ignores line as well as synchronous machine resistance and shunt capacitances.  (2) assumes accelerating power acting on the rotor as constant.  (3) ignores the effect of voltage ... inherent damping present in the machine.  (4) takes into consideration the possibility of machine losing synchronism after it has survived during the first swing.

Answer :

1

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Description :

During a disturbance on a synchronous machine, the rotor swings form A to B before finally setting down to steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at point(s)

Answer :

During a disturbance on a synchronous machine, the rotor swings form A to B before finally setting down to steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at point(s) only at C

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Description :

Answer :

Synchronsizing power of a synchronous machine is inversely proportional to the synchronous reactance.

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Description :

Answer :

Sparking at the commutator of a D.C. motor may result in damage to commutator segments, damage to commutator insulation, increased power consumption.

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142 views 1 answer
Description :

Write down the steps involved for internal thread cutting on lathe machine.

Answer :

Steps involved for internal thread cutting on lathe machine  1) Hole is first bored to the root diameter of the thread. 2) Tool is fixed on the tool post or on the boring bar adjusted the angle of ... the start. 10) Keep going until the calculated depth of cut has been reached on the top slide.

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Description :

Types of slotting machine

Answer :

1. Puncher slotter 2. Precision slotter 3. Production slotter  Working Principle of Slotting machine:- The slotting machine is a reciprocating machine tool in which, The vertical slide holding the cutting ... longitudinal and cross feeds, a rotary feed motion is also provided in the work table. 

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