menu search
person
thumb_up_alt 0 like thumb_down_alt 0 dislike
2.9k views

1 Answer

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
← Prev Question Next Question →

Related questions

Description :

Answer :

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
412 views 1 answer
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.

thumb_up_alt 0 like thumb_down_alt 0 dislike
141 views 1 answer
Description :

Answer :

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
111 views 1 answer
thumb_up_alt 0 like thumb_down_alt 0 dislike
70 views 0 answers
Description :

Answer :

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
121 views 1 answer
Description :

Answer :

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
69 views 1 answer
Description :

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.

thumb_up_alt 0 like thumb_down_alt 0 dislike
139 views 1 answer
Description :

The function of a brush and commutator arrangement in a dc motor is to  (1) produce unidirectional torque (2) produce unidirectional current in the armature (3) help in changing the direction of rotation of the armature (4) reduce sparking

Answer :

The function of a brush and commutator arrangement in a dc motor is to produce unidirectional torque

thumb_up_alt 0 like thumb_down_alt 0 dislike
1.7k views 1 answer
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.

thumb_up_alt 0 like thumb_down_alt 0 dislike
168 views 1 answer
Description :

Answer :

The number of brushes in a commutator depends on amount of current to be collected.

thumb_up_alt 0 like thumb_down_alt 0 dislike
139 views 1 answer
Description :

Answer :

In a commutator mica is harder than copper.

thumb_up_alt 0 like thumb_down_alt 0 dislike
50 views 1 answer
Description :

Answer :

The insulating material used between the commutator segments is normally mica.

thumb_up_alt 0 like thumb_down_alt 0 dislike
217 views 1 answer
Description :

Answer :

The material for commutator brushes is generally carbon.

thumb_up_alt 0 like thumb_down_alt 0 dislike
108 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

thumb_up_alt 0 like thumb_down_alt 0 dislike
89 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

thumb_up_alt 0 like thumb_down_alt 0 dislike
222 views 1 answer
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

thumb_up_alt 0 like thumb_down_alt 0 dislike
102 views 1 answer
Description :

Answer :

Copper losses,iron losses,variable losses , constant losees

thumb_up_alt 0 like thumb_down_alt 0 dislike
158 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.

thumb_up_alt 0 like thumb_down_alt 0 dislike
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 % .

thumb_up_alt 0 like thumb_down_alt 0 dislike
99 views 1 answer
Description :

Answer :

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

thumb_up_alt 1 like thumb_down_alt 0 dislike
91 views 1 answer
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

thumb_up_alt 0 like thumb_down_alt 0 dislike
81 views 1 answer
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

thumb_up_alt 0 like thumb_down_alt 0 dislike
327 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

thumb_up_alt 0 like thumb_down_alt 0 dislike
529 views 1 answer
Description :

Why poles of dc machine are laminated?

Answer :

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
54 views 1 answer
Description :

Brushes of DC machine are made up of ?

Answer :

Brushes of DC machine are made up of carbon.

thumb_up_alt 0 like thumb_down_alt 0 dislike
136 views 1 answer
Description :

Answer :

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
111 views 1 answer
Description :

Answer :

In D.C. generators, the brushes on commutator remain in contact with conductors which lie under interpolar region.

thumb_up_alt 0 like thumb_down_alt 0 dislike
197 views 1 answer
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.

thumb_up_alt 0 like thumb_down_alt 0 dislike
116 views 1 answer
Description :

Which of the following does not have a commutator? A) Dynamo B) Induction motor C) Universal motor D) None of these

Answer :

Which of the following does not have a commutator? A) Dynamo B) Induction motor C) Universal motor D) None of these

thumb_up_alt 0 like thumb_down_alt 0 dislike
169 views 1 answer
Description :

Number of commutator bars for a 4-pole, 2-layer, DC lap winding with 24 slots and one conductor per layer is (A) 48 (B) 24 (C) 192 (D) 96

Answer :

Number of commutator bars for a 4-pole, 2-layer, DC lap winding with 24 slots and one conductor per layer is 24

thumb_up_alt 0 like thumb_down_alt 0 dislike
760 views 1 answer
Description :

Answer :

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
154 views 1 answer
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

thumb_up_alt 1 like thumb_down_alt 0 dislike
260 views 2 answers
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

thumb_up_alt 0 like thumb_down_alt 0 dislike
172 views 1 answer
Description :

Answer :

To limit the operating temperature an electrical machine should have proper current rating.

thumb_up_alt 0 like thumb_down_alt 0 dislike
68 views 1 answer
Description :

Answer :

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
96 views 1 answer
Description :

Answer :

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
384 views 1 answer
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.

thumb_up_alt 0 like thumb_down_alt 0 dislike
103 views 1 answer
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 

thumb_up_alt 0 like thumb_down_alt 0 dislike
365 views 1 answer
Description :

What is fuzzy logic in a washing machine?

thumb_up_alt 0 like thumb_down_alt 0 dislike
73 views 0 answers
Description :

Answer :

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
142 views 1 answer
Description :

Answer :

In D.C. generators the pole shoes are fastened to the pole core by counter sunk screws.

thumb_up_alt 0 like thumb_down_alt 0 dislike
156 views 1 answer
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.

thumb_up_alt 0 like thumb_down_alt 0 dislike
49 views 1 answer
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

thumb_up_alt 0 like thumb_down_alt 0 dislike
43 views 1 answer
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 

thumb_up_alt 0 like thumb_down_alt 0 dislike
122 views 1 answer
Description :

Answer :

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
75 views 1 answer
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.

thumb_up_alt 0 like thumb_down_alt 0 dislike
18 views 1 answer
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.

thumb_up_alt 0 like thumb_down_alt 0 dislike
12 views 1 answer
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

thumb_up_alt 0 like thumb_down_alt 0 dislike
126 views 1 answer
Description :

Answer :

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

thumb_up_alt 0 like thumb_down_alt 0 dislike
72 views 1 answer
editAsk a Question
...