Open circuited armature coil of a D.C. machine is?

by

1 Answer

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.

by

Related questions

Armature coil is short circuited by brushes when it lies?

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

If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will?

Last Answer : If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will stop.

A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2

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

The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors

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

Aluminium is not used as winding wire for the armature of a dc machine because

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

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

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 

The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole)

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

The armature core of a D.C. generator is usually made of?

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

The demagnetising component of armature reaction in a D.C. generator?

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

In a D.C. machine stray loss is the sum of?

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

To avoid formation of grooves in the commutator of a D.C. machine?

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

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

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

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

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

In a four-pole D.C. machine?

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

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

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.

A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance

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

Last 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

In dc machines, the armature windings are placed on the rotor because of the necessity for

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

Last Answer : 3  Commutation

The normal value of the armature resistance of a d.c. motor is?

Description : The normal value of the armature resistance of a d.c. motor is?

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

When the armature of a D.C. motor rotates, e.m.f. induced is

Last Answer : When the armature of a D.C. motor rotates, e.m.f. induced is back e.m.f.

The armature voltage control of D.C. motor provides?

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

The armature torque of the D.C. shunt motor is proportional to?

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

In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be?

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.

Why is the armature of DC generator laminated?

Description : Why is the armature of DC generator laminated?

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

Armature control of DC motor

Description : Armature control of DC motor

Last Answer : Armature control of DC motor

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

Last Answer : Armature reaction of an unsaturated D.C. machine is crossmagnetising.

A d.c. source has an open circuit voltage of 30 V and an internal resistance of 1.5 Ohm. A resistive load is ...

Description : A d.c. source has an open circuit voltage of 30 V and an internal resistance of 1.5 Ohm. A resistive load is connected to the source. Maximum power dissipated in the load is (A) 300 W (B) 150 W (C) 45 W (D) 20 W

Last Answer : A d.c. source has an open circuit voltage of 30 V and an internal resistance of 1.5 Ohm. A resistive load is connected to the source. Maximum power dissipated in the load is 150 W

Armature reaction in a generator results in?

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

The commutator segments are connected to the armature conductors by means of?

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

The resistance of armature winding depends on?

Last Answer : The resistance of armature winding depends on length of conductor, cross-sectional area of the conductor, number of conductors.

Why poles of dc machine are laminated?

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.

Losses in dc machine..?

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

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

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

In a dc machine, interpoles are used to

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

The magnetic neutral plane shifts in a dc machine

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

What is the percentage of stray losses in DC machine?

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

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

Brushes of DC machine are made up of ?

Description : Brushes of DC machine are made up of ?

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

what are the losses in DC machine?

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