# Brushes of DC machine are made up of ?

Brushes of DC machine are made up of ?

Brushes of DC machine are made up of carbon.

## Related questions

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

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

Description : In a DC motor, it is important to place the brushes along ______ A) Magnetic Neutral Axis B) Normal Geometric Axis C) Nominal Geometric Axis D) None of these

Answer : In a DC motor, it is important to place the brushes along Magnetic Neutral Axis

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

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 : 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

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

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

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 : Why poles of dc machine are laminated?

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

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

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

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.

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

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

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

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

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

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

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

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.

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

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

Answer : The rotor of a hysteresis motor is made of chrome steel.

Answer : The rapid wear of brushes takes place due to abrasion from dust, excessive spring pressure, rough commutator bars, high mica insulation between com-mutation bars.

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

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

Answer : The material for commutator brushes is generally carbon.

Answer : In lap winding, the number of brushes is always same as the number of poles.

Description : In DC generators lamination core are generally made of?

Answer : In DC generators lamination core are generally made of silicon steel.

Description :  Analyze the differences of FOC and DTC. The switching frequency of FOC is 1.3 kHz and the average switching frequency of DTC is the same.

Description : D.C. shunt relays are made of?

Answer : D.C. shunt relays are made of many turns of thin wire.

Description : UNIT 1 fundamentals of AC rotating machine Contents 1.1 Introduction 1.2 Advantages 1.3 Parts of AC machines 1.4 Synchronous speed 1.5 AC winding 1.6 Winding factor ( ... alternator or generator 1.9 Numericals 1.10 Harmonic 1.11 Slot harmonics 1.12 Harmonics minimization

Answer : 1.2 Advantages: In practices most of alternator have rotating magnetic field type construction with stationary armature due to following reason. The generation level of AC voltage may be in the range ... at high speed. Only two Slip rings are required to excited the field by AC supply.

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

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

Description : Torque angle for the synchronous machine is the angle between (A) stator magnetic field and rotor magnetic field (B) stator magnetic field and net magnetic field in the air gap (C) rotor magnetic field and net magnetic field in the air gap (D) excitation voltage and impedance voltage drop

Answer : Torque angle for the synchronous machine is the angle between rotor magnetic field and net magnetic field in the air gap

Description : The IC chips, used in computers, is made of  (1) Iron oxide (2) Silicon (3) Graphite (4) Silica

Answer : 2 These are made on silicon wafers which is aa semi conductor. ...

Description : A switch tail ring counter is made by using a single D-FF. The resulting circuit is (A) T-FF (B) D-FF (C) SR-FF (D) JK-FF

Answer : A switch tail ring counter is made by using a single D-FF. The resulting circuit is T-FF

Description : A synchronous motor can be made self starting by providing?

Answer : A synchronous motor can be made self-starting by providing damper bar.

Description : I got some grapic drawing questions guys and I need to see the answers immediately.Stator voltage curve for each four different start up methods.

Description : The number of brushes in a 6-pole double-layer lap wound dc machine is (A) 8 (B) 6 (C) 4 (D) 2

Description : In dc machines, the armature windings are placed on the rotor because of the necessity for  (1) electromechanical energy conversion (2) generation of voltage (3) commutation (4) development of torque

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 : What are the speed control methods of dc motor?

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

Description : Capsule coffee machine. What are the advantages?

Answer : Having a coffee maker in the house helps us to easily cheer up and brighten up the beginning of the upcoming day in the morning, especially if the weather is unpleasant. A cup of hot ... favor is the fact that the profile of this manufacturer is precisely capsule coffee makers and coffee capsules.

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.

Description : Describe the reason of using dc series motor for electric trains.

Answer : Electric trains require an inverse torque speed characteristics for proper operation. That is a higher torque is required at start (when speed is nil or low) and as the train picks up ... torque - speed characteristics of DC series motors match, these motors are suitable for electric trains

Description : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be

Answer : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be 474 V

Description : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is

Answer : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is 36 Ohm

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.

← Prev Question Next Question →