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 :
It is the wire wound around a aluminium metal it is found commonly in transformers or motors
asked
Jul 27, 2019
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
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 : The normal value of the armature resistance of a d.c. motor is?
Answer :
The normal value of the armature resistance of a d.c. motor is 0.5.
asked
Mar 26, 2018
by
anonymous
Answer :
Armature reaction in a generator results in demagnetisation of leading pole tip and magnetisation of trailing pole tip.
asked
Mar 21, 2018
by
anonymous
Answer :
A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave will be of 5 Hz.
asked
Mar 21, 2018
by
anonymous
Answer :
Armature coil is short circuited by brushes when it lies along neutral axis.
asked
Mar 21, 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 :
The armature core of a D.C. generator is usually made of silicon steel.
asked
Mar 20, 2018
by
anonymous
Answer :
The demagnetising component of armature reaction in a D.C. generator reduces generator e.m.f.
asked
Mar 20, 2018
by
anonymous
Answer :
Armature reaction of an unsaturated D.C. machine is crossmagnetising.
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
asked
Mar 20, 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 :
In D.C. generators, lap winding is used for low voltage, high current.
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 case of D.C. machine winding, number of commutator segments is equal to number of armature coils.
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
Description : Write any two factors on which earth resistance depends.
Answer :
Factors on which earth resistance depends: (1) The shape and material used for the electrode (2) Depth of the electrode in the ground. (3) The specific resistance of the soil around the electrode (4) Moisture content in the soil. (5) Nature of soil
asked
Sep 6, 2018
by
anonymous
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
Answer :
3 Commutation
asked
May 1, 2018
by
anonymous
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
asked
Apr 29, 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 :
The critical resistance of the D.C. generator is the resistance of field.
asked
Mar 21, 2018
by
anonymous
Answer :
In a D.C. generator, the critical resistance refers to the resistance of field.
asked
Mar 21, 2018
by
anonymous
Description : Define armature reaction in an alternator. Explain the effect of armature reaction at various P.F. of loads of alternator.
Answer :
Armature Reaction: The effect of armature flux on main flux is called as armature reaction. Armature Reaction at Various Power Factors: When armature is loaded, the armature flux modifies ... lagging p.f. For capacitive loads the effect of flux is partly distorting and partly strengthening.
asked
May 7, 2020
by
anonymous
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
asked
May 1, 2018
by
anonymous
Description : In a 3 -phase alternator, if there is only magnetizing armature reaction, the load is : (A) capacitive (B) inductive (C) resistive (D) inductive and resistive
Answer :
In a 3 -phase alternator, if there is only magnetizing armature reaction, the load is : capacitive
asked
Apr 30, 2018
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 : What is the effect of armature reaction? A) Demagnetization of the main field B) Demagnetization of the brushes C) Cross-magnetization of the brushes D) None of these
Answer :
What is the effect of armature reaction? A) Demagnetization of the main field B) Demagnetization of the brushes C) Cross-magnetization of the brushes D) None of these
asked
Apr 29, 2018
by
anonymous
Description : The armature reaction in a synchronous generator supplying leading power factor load is (A) magnetizing (B) demagnetizing (C) demagnetizing and cross-magnetizing (D) magnetizing and cross-magnetizing
Answer :
The armature reaction in a synchronous generator supplying leading power factor load is magnetizing and cross-magnetizing
asked
Apr 28, 2018
by
anonymous
Description : The induced e.m.f. in the armature conductors of a d.c. motor is?
Answer :
The induced e.m.f. in the armature conductors of a d.c. motor is sinusoidal.
asked
Mar 26, 2018
by
anonymous
Answer :
When the armature of a D.C. motor rotates, e.m.f. induced is back e.m.f.
asked
Mar 20, 2018
by
anonymous
Answer :
The armature voltage control of D.C. motor provides constant torque drive.
asked
Mar 20, 2018
by
anonymous
Answer :
The armature torque of the D.C. shunt motor is proportional to armature current.
asked
Mar 20, 2018
by
anonymous
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.
asked
Mar 20, 2018
by
anonymous
Answer :
In a A.C. series motor armature coils are usually connected to commutator through resistance.
asked
Mar 20, 2018
by
anonymous
Answer :
In a synchronous motor, the armature current has large values for high and low excitation.
Answer :
The armature current of the synchronous motor has large values for low and high excitation.
asked
Mar 20, 2018
by
anonymous
Description : Why is the armature of DC generator laminated?
Answer :
The armature of DC generator is laminated to reduce eddy current losses.
asked
Mar 3, 2018
by
anonymous
Description : Armature control of DC motor
Answer :
Armature control of DC motor
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
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 : 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 : 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 :
In D.C. machines fractional pitch winding is used to reduce the sparking.
asked
Mar 20, 2018
by
anonymous
Answer :
The starting winding of a single-phase motor is placed in stator.
asked
Mar 20, 2018
by
anonymous