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Answer :

Armature reaction of an unsaturated D.C. machine is crossmagnetising.

Related questions

Last Answer : Armature reaction in a generator results in demagnetisation of leading pole tip and magnetisation of trailing pole tip.

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

Description : Define armature reaction in an alternator. Explain the effect of armature reaction at various P.F. of loads of alternator.

Last Answer : Armature Reaction: The effect of armature flux on main flux is called as armature reaction.  Armature Reaction at Various Power Factors: When armature is loaded, the armature flux modifies ... lagging p.f. For capacitive loads the effect of flux is partly distorting and partly strengthening.

Description : In a 3 -phase alternator, if there is only magnetizing armature reaction, the load is :  (A) capacitive (B) inductive (C) resistive (D) inductive and resistive

Last Answer : In a 3 -phase alternator, if there is only magnetizing armature reaction, the load is : capacitive 

Description : What is the effect of armature reaction? A) Demagnetization of the main field B) Demagnetization of the brushes C) Cross-magnetization of the brushes D) None of these

Last Answer : What is the effect of armature reaction? A) Demagnetization of the main field B) Demagnetization of the brushes C) Cross-magnetization of the brushes D) None of these

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

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

Last 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.

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

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

Last Answer : The commutator segments are connected to the armature conductors by means of copper lugs.

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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

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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

Last 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 

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

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

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

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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 ... ) the thermal conductivity of aluminium is low (4) aluminium has low conductivity as compared to copper

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Last Answer : It is the wire wound around a aluminium metal it is found commonly in transformers or motors

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Last Answer : 3  Commutation

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Last Answer : The induced e.m.f. in the armature conductors of a d.c. motor is sinusoidal.

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Last Answer : The normal value of the armature resistance of a d.c. motor is 0.5.

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Last Answer : The armature voltage control of D.C. motor provides constant torque drive.

Last Answer : The armature torque of the D.C. shunt motor is proportional to armature current.

Last Answer : In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be more than full-load current.

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

Last Answer : In a synchronous motor, the armature current has large values for high and low excitation.

Last Answer : The armature current of the synchronous motor has large values for low and high excitation.

Description : Why is the armature of DC generator laminated?

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

Description : Armature control of DC motor

Last Answer : Armature control of DC motor

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Last Answer : In a separately excited generator supplying rated load the armature reaction is always present.

Description : A 8-pole, DC generator has a simplex wave-wound armature containing 32 coils of 6 turns each. Its flux per pole is 0.06 Wb. The machine is running at 250 rpm. The induced armature voltage is  (A) 96 V (B) 192 V (C) 384 V (D) 768 V

Last Answer : A 8-pole, DC generator has a simplex wave-wound armature containing 32 coils of 6 turns each. Its flux per pole is 0.06 Wb. The machine is running at 250 rpm. The induced armature voltage is 384 V

Description : A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave?

Last Answer : A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave will be of 5 Hz.

Description : The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be?

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Last Answer : Equilizer rings are required in case armature is lap wound.

Last Answer : In D.C. generators, current to the external circuit from armature is given through commutator commutator.

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. ?

Last Answer : Wave winding

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

Last 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.

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

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

Description : Eddy currents are induced in the pole shoes of a D.C. machine due to?

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

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

Last Answer : Copper brushes in D.C. machine are used where low voltage and high currents are involved.

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