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
asked
May 3, 2018
by
anonymous
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
asked
Apr 29, 2018
by
anonymous
Answer :
To avoid formation of grooves in the commutator of a D.C. machine the brushes of opposite polarity should track each other.
asked
Mar 21, 2018
by
anonymous
Answer :
In a D.C. machine stray loss is the sum of iron loss and mechanical loss.
asked
Mar 21, 2018
by
anonymous
asked
Mar 20, 2018
by
anonymous
Answer :
Iron losses in a D.C. machine are independent of variations in load.
asked
Mar 20, 2018
by
anonymous
Answer :
In a four-pole D.C. machine alternate poles are north and south.
asked
Mar 20, 2018
by
anonymous
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.
asked
Mar 20, 2018
by
anonymous
Answer :
In D.C. machines fractional pitch winding is used to reduce the sparking.
asked
Mar 20, 2018
by
anonymous
Answer :
In the case of lap winding resultant pitch is difference of front and back pitches.
asked
Mar 20, 2018
by
anonymous
Answer :
In lap winding, the number of brushes is always same as the number of poles.
asked
Mar 20, 2018
by
anonymous
Answer :
In a D.C. generator in case the resistance of the field winding is increased, then output voltage will decrease.
asked
Mar 21, 2018
by
anonymous
Answer :
In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be 8.
asked
Mar 20, 2018
by
anonymous
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
asked
Apr 29, 2018
by
anonymous
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
asked
May 3, 2018
by
anonymous
Answer :
In D.C. generators, lap winding is used for low voltage, high current.
asked
Mar 20, 2018
by
anonymous
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.
asked
Jul 27, 2019
by
anonymous
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
asked
Apr 29, 2018
by
anonymous
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
asked
Apr 28, 2018
by
anonymous
Description : What is the percentage of stray losses in DC machine?
Answer :
Percentage of stray losses in DC machine is about 1 % .
asked
Mar 8, 2018
by
anonymous
Answer :
Iron loss, copper loss and mechanical losses these are the losses in DC machine.
asked
Sep 27, 2017
by
anonymous
Description : Why poles of dc machine are laminated?
Answer :
Poles of DC machines are laminated to reduce the eddy current losses in the poles.
asked
Apr 27, 2020
by
anonymous
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
asked
May 8, 2018
by
anonymous
Description : Brushes of DC machine are made up of ?
Answer :
Brushes of DC machine are made up of carbon.
asked
Mar 3, 2018
by
anonymous
Answer :
In D.C. generators, the brushes on commutator remain in contact with conductors which lie under interpolar region.
asked
Mar 20, 2018
by
anonymous
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.
asked
Mar 21, 2018
by
anonymous
Answer :
Wave winding is composed of that even number which is exact multiple of poles + 2.
asked
Mar 21, 2018
by
anonymous
Answer :
Lap winding is composed of any even number of conductors.
asked
Mar 21, 2018
by
anonymous
Answer :
The resistance of armature winding depends on length of conductor, cross-sectional area of the conductor, number of conductors.
asked
Mar 20, 2018
by
anonymous
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
asked
Apr 30, 2018
by
anonymous
Answer :
Eddy currents are induced in the pole shoes of a D.C. machine due to relative rotation between field and armature.
asked
Mar 20, 2018
by
anonymous
Answer :
In case of conductively compensated D.C. series motors, the compensating winding is provided in series with armature winding.
asked
Mar 20, 2018
by
anonymous
Answer :
The commutator segments are connected to the armature conductors by means of copper lugs.
asked
Mar 20, 2018
by
anonymous
Answer :
yes High Voltage side of Transformer winding have more number of turns. and low voltage side of Transformer winding have less number of turns.
asked
Sep 30, 2017
by
anonymous
Description : State the function of following parts of DC motor : i) Yoke ii) Poles iii) Field winding iv) Commutator.
Answer :
Function : i) Yoke: The yoke serves the following two purposes. i) It supports the other components such as poles and provides mechanical protection for whole machine. ii) It forms a part of ... one pole to another and thus to help the motor to develop a continuous and unidirectional torque
asked
Jul 30, 2019
by
anonymous
Answer :
The insulating material used between the commutator segments is normally mica.
asked
Mar 20, 2018
by
anonymous
Answer :
In A.C. series motor compensating winding is employed to reduce sparking at the brushes.
asked
Mar 20, 2018
by
anonymous
Answer :
In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when number of poles is 2.
asked
Mar 20, 2018
by
anonymous
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. ?
Answer :
Wave winding
asked
Mar 20, 2018
by
anonymous
Description : Damper winding is provided in 3 phase synchronous motors to :
Answer :
Damper winding is provided in 3 phase synchronous motors to : provide starting torque and prevent hunting
asked
Apr 29, 2018
by
anonymous
Answer :
The purpose of stator winding in the compensated repulsion motor is to improve power factor and provide better speed regulation.
asked
Mar 20, 2018
by
anonymous
Answer :
In a capacitor start and run motors the function of the running capacitor in series with the auxiliary winding is to improve power factor.
asked
Mar 20, 2018
by
anonymous
Description : The damping winding in synchronous motor is generally used to?
Answer :
The damping winding in synchronous motor is generally used to provide starting torque and prevent hunting.
asked
Mar 18, 2018
by
anonymous
Description : A _________ is used to measure the stator % winding temperature of the generator. (A) Thermocouple (B) Pyrometer (C) Resistance thermometer (D) Thermometer
Answer :
A Resistance thermometer is used to measure the stator % winding temperature of the generator.
asked
May 8, 2018
by
anonymous
Description : The running winding of a single phase motor on testing with meggar is found to be ground. Most probable location of the ground will be?
Answer :
The running winding of a single phase motor on testing with meggar is found to be ground. Most probable location of the ground will be at the slot edge where coil enters or comes out of the slot.
asked
Mar 20, 2018
by
anonymous
Answer :
A centrifugal switch is used to disconnect starting winding when motor has picked up about 50 to 70 per cent of rated speed.
asked
Mar 20, 2018
by
anonymous
Description : State advantages of short pitch winding over full pitch winding in alternators.
Answer :
Advantages of Short Pitch Winding over Full Pitch Winding in Alternators: 1) Short pitching reduces the amount of copper needed for end connection when compared with full pitched coil. 2) They ... reduced, thereby increasing the efficiency. 4) The power quality of generated emf is improved.
asked
May 7, 2020
by
anonymous
Description : Damper winding in a synchronous motor
Answer :
Damper winding in a synchronous motor Serves to start the motor.
asked
May 8, 2018
by
anonymous
Description : A certain transformer has 200 turns in the primary winding, 50 turns in the secondary winding and 120 volts applied to the primary. What is the voltage across the secondary? (A) 30 Volts (B) 480 Volts (C) 120 Volts (D) 60 Volts
Answer :
A certain transformer has 200 turns in the primary winding, 50 turns in the secondary winding and 120 volts applied to the primary. What is the voltage across the secondary? (A) 30 Volts (B) 480 Volts (C) 120 Volts (D) 60 Volts
asked
May 8, 2018
by
anonymous