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Answer :

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

Related questions

Description : What is the percentage of stray losses in DC machine?

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

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

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

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

Description : What arc the errors occurring in measuring devices due to stray magnetic field and temp '? Explain how to compensate them.

Last Answer : 1. Error due to stray magnetic fields-   Main magnetic field gets disturbed by external magnetic fields known as stray magnetic fields.  2. Compensation technique   To avoid this error, ... resistance alloy having a negligible resistance temp coefficient in the ratio of 1:10 for pressure coil 

Last Answer : To avoid the effect of stray magnetic field in A.C. bridges we can use magnetic screening.

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

Last 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 : Why poles of dc machine are laminated?

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

Last Answer : Copper losses,iron losses,variable losses , constant losees

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

Last 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.

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

Last 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 : 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

Last 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

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

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

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

Last 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

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

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

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

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

Description : Brushes of DC machine are made up of ?

Last Answer : Brushes of DC machine are made up of carbon.

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

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.

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.

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Last Answer : Have you tried a different method of approach? A way that she won’t be able to ignore?

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Last Answer : A good cry and a few beers.

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Last Answer : Corona is nothing but the ionization of surrounding air around the conductor which produces hissing noise,

Description : State the factors affecting hysteresis loss.

Last Answer : i) Flux density ii) Frequency iii) Volume of the magnetic material iv) Nature of magnetic material

Description : A 40 kVA transformer has a core loss of 400 W and a full load copper loss of 800 W. The proportion of full load at maximum efficiency is

Last Answer : A 40 kVA transformer has a core loss of 400 W and a full load copper loss of 800 W. The proportion of full load at maximum efficiency is 0.707

Description : At full -load of a transformer, the iron loss and copper loss are 3000 W and 4000 W respectively. Then total loss at maximum efficiency is :  (A) 7000 W (B) 6000 W (C) 8000 W (D) 4000 W

Last Answer : At full -load of a transformer, the iron loss and copper loss are 3000 W and 4000 W respectively. Then total loss at maximum efficiency is : 6000 W

Description : Corona loss in transmission lines can be reduced by (A) using small diameter conductors (B) using bundled conductors (C) using less spacing between conductors (D) increasing the transmission line voltage

Last Answer : Corona loss in transmission lines can be reduced by using bundled conductors

Description : Dielectric loss in a capacitor is best measured by (A) Wien Bridge (B) Schering Bridge (C) Anderson Bridge (D) Heaviside-Campbell Equal Ratio Bridge

Last Answer : Dielectric loss in a capacitor is best measured by Schering Bridge

Description : A ferrite core has less eddy current loss than an iron core because?

Last Answer : A ferrite core has less eddy current loss than an iron core because ferrites have high hysteresis.

Description : In a magnetic material hysteresis loss takes place primarily due to?

Last Answer : In a magnetic material hysteresis loss takes place primarily due to it high retentivity.

Description : In a circuit containing R, L and C, power loss can take place in?

Last Answer : In a circuit containing R, L and C, power loss can take place in R only.

Description : In a loss-free R-L-C circuit the transient current is?

Last Answer : In a loss-free R-L-C circuit the transient current is sinusoidal.

Last Answer : If the current in a capacitor leads the voltage by 80°, the loss angle of the capacitor is 10°.

Last Answer : If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then the stator current will be zero.

Last Answer : The power loss is an important factor for the design of transmission line.

Description : In an actual transformer the iron loss remains practically constant from no load to full load because?

Last Answer : In an actual transformer the iron loss remains practically constant from no load to full load because core flux remains practically constant.

Last Answer : If the supply frequency to the transformer is increased, the iron loss will increase.

Last Answer : Iron loss of a transformer can be measured by low power factor wattmeter.

Description : What is the difference between eddy current and hysteresis loss?

Last Answer : Loss occurred by magnetising and demagnetising process is called histerisis loss and the current flowed due to the magnetic field produced by the electric field applied is called eddy current losses