Armature of an electrical machine is the

Armature of an electrical machine is the (A) stator part of the machine (B) rotor part of the machine (C) yoke of the machine (D) none of these
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Answer :

Armature of an electrical machine is the rotor part of the machine

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Related questions

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

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 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

A pole pitch in electrical machine is:

Description : A pole pitch in electrical machine is: (1) Equal to 180° electrical (2) Equal to 180° mechanical (3) Less than 180° electrical (4) Greater Than 180° electrical

Last Answer : A pole pitch in electrical machine is: Equal to 180° electrical

A rotating electrical machine its self-inductances of both the stator and the rotor windings, independent of

Description : A rotating electrical machine its self-inductances of both the stator and the rotor windings, independent of the rotor position will be definitely not develop  (A) starting torque (B) synchronizing torque (C) hysteresis torque (D) reluctance torque

Last Answer : A rotating electrical machine its self-inductances of both the stator and the rotor windings, independent of the rotor position will be definitely not develop synchronizing torque

Total electrical degrees for a 4 pole AC machine is equal to

Description : Total electrical degrees for a 4 pole AC machine is equal to

Last Answer : Total electrical degrees for a 4 pole AC machine is equal to 720 ̊

If the current in the armature of do series motor is reduced to 5%, the torque of the motor will become:

Description : If the current in the armature of do series motor is reduced to 5%, the torque of the motor will become: (1) 50% of the previous value (2) 25% of the previous value (3) 150% of the previous value (4) 125% of the previous value

Last Answer : If the current in the armature of do series motor is reduced to 5%, the torque of the motor will become: 25% of the previous value

The armature resistance of a permanent magnet dc motor is 0.8 Ohm. At no load, the motor draws 1.5 A from

Description : The armature resistance of a permanent magnet dc motor is 0.8 Ohm. At no load, the motor draws 1.5 A from a supply voltage of 25 V and runs at 1500 rpm. The efficiency of the motor while it is operating on load at 1500 ... .5 A from the same source will be  (A) 48.0% (B) 57.1% (C) 59.2% (D) 88.8%

Last Answer : The armature resistance of a permanent magnet dc motor is 0.8 Ohm. At no load, the motor draws 1.5 A from a supply voltage of 25 V and runs at 1500 rpm. The efficiency of the motor while it is operating on load at 1500 rpm drawing a current of 3.5 A from the same source will be 48.0%

When running under no-load condition and with over excitation, armature current Ia drawn by a synchronous motor

Description : When running under no-load condition and with over excitation, armature current Ia drawn by a synchronous motor

Last Answer : When running under no-load condition and with over excitation, armature current Ia drawn by a synchronous motor Leads the applied voltage

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 armature reaction in a synchronous generator supplying leading power factor load is

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

Last Answer : The armature reaction in a synchronous generator supplying leading power factor load is magnetizing and cross-magnetizing

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.

The current drawn by the armature of D.C. motor is directly proportional to?

Last Answer : The current drawn by the armature of D.C. motor is directly proportional to the torque required.

In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to?

Last Answer : In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to 25% of the previous value.

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.

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

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

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

The electrical device shown in the illustration is a/an _____________. EL-0077 A. operating coil B. indicating lamp C. motor armature D. potentiometer

Description : The electrical device shown in the illustration is a/an _____________. EL-0077 A. operating coil B. indicating lamp C. motor armature D. potentiometer

Last Answer : Answer: D

The air gap in an induction motor should be checked periodically with a feeler gage to detect ____________. A. rotor contact with the laminations B. changes in armature magnetic strength C. excessive bearing wear D. electrical damage to the rotor

Description : The air gap in an induction motor should be checked periodically with a feeler gage to detect ____________. A. rotor contact with the laminations B. changes in armature magnetic strength C. excessive bearing wear D. electrical damage to the rotor

Last Answer : Answer: C

Basic electrical motor action depends on _______________. A. a conductor rotated within a magnetic field B. a current carrying conductor placed in a magnetic field C. the relative force of the commutator and commutating poles D. the relative force of the armature and interpoles

Description : Basic electrical motor action depends on _______________. A. a conductor rotated within a magnetic field B. a current carrying conductor placed in a magnetic field C. the relative force of the commutator and commutating poles D. the relative force of the armature and interpoles

Last Answer : Answer: B

An electrical device which employs a stationary armature and a rotating electromagnetic field is used aboard ship as a ____________. A. magnetic amplifier B. ship's service alternator C. three-wire DC generator D. saturable core reactor

Description : An electrical device which employs a stationary armature and a rotating electromagnetic field is used aboard ship as a ____________. A. magnetic amplifier B. ship's service alternator C. three-wire DC generator D. saturable core reactor

Last Answer : Answer: B

Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in armature reaction are compensated for by the __________ A. governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay

Description : Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in ... . governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay

Last Answer : Answer: B

Straight silicon steel (containing Si from 0.5 to 5%) because of their low hysteresis loss and high magnetic permeability are used for electrical appliances. Which of the following electrical appliances made of silicon steel contains maximum percentage of silicon (about 4%)? (A) Armature of small motors/generators (B) Generators and small motors (C) Induction motors (D) High frequency transformers

Description : Straight silicon steel (containing Si from 0.5 to 5%) because of their low hysteresis loss and high magnetic permeability are used for electrical appliances. Which of the following electrical ... /generators (B) Generators and small motors (C) Induction motors (D) High frequency transformers

Last Answer : (D) High frequency transformers

A flickering ground detection lamp on a DC system would indicate a _____________. A. multiple-ground condition in the distribution system B. ground in an armature coil of an operating machine C. ground in a motor accompanied with a short D. short between two adjacent bars of the generator commutator

Description : A flickering ground detection lamp on a DC system would indicate a _____________. A. multiple-ground condition in the distribution system B. ground in an armature coil of an operating machine C. ground in a motor accompanied with a short D. short between two adjacent bars of the generator commutator

Last Answer : Answer: B

In addition to undercutting the mica, proper maintenance of a D.C. motor's commutator includes _______________. A. side-cutting the copper segments and insulating the slots B. coating the copper surface with light machine oil for the first four hours of operation C. baking the armature in an oven at a maximum of 95°C for not over 8 hours D. all of the above

Description : In addition to undercutting the mica, proper maintenance of a D.C. motor's commutator includes _______________. A. side-cutting the copper segments and insulating the slots B. coating the copper surface with light machine ... in an oven at a maximum of 95°C for not over 8 hours D. all of the above

Last Answer : Answer: A

To carry out an insulation resistance test, one terminal of the megohmmeter should be connected to the winding, with the other terminal being connected to the ____________________. A. power supply B. variable resistor C. frame of the machine D. armature

Description : To carry out an insulation resistance test, one terminal of the megohmmeter should be connected to the winding, with the other terminal being connected to the ____________________. A. power supply B. variable resistor C. frame of the machine D. armature

Last Answer : Answer: C

Before testing insulation with a megohmmeter, the windings of large machines should be grounded for about 15 minutes just prior to the test, because the ___________. A. static charge of the machine may give a false reading B. armature will have a greater number of leakage paths C. insulation may be damaged D. insulation may be covered with moisture

Description : Before testing insulation with a megohmmeter, the windings of large machines should be grounded for about 15 minutes just prior to the test, because the ___________. A. static charge of the machine ... number of leakage paths C. insulation may be damaged D. insulation may be covered with moisture

Last Answer : Answer: A

Which one of the following statements for a dc machine which is provided with inter pole winding (IW) as well as compensating winding (CW) is correct a) Both IW and CW are connected in series with Armature winding b) Both IW and CW are connected in parallel with Armature winding c) IW connected in series but CW is connected in parallel with Armature winding d) CW connected in series but IW is connected in parallel with Armature winding

Description : Which one of the following statements for a dc machine which is provided with inter pole winding (IW) as well as compensating winding (CW) is correct a) Both IW and CW are connected in ... parallel with Armature winding d) CW connected in series but IW is connected in parallel with Armature winding

Last Answer : Ans: Both IW and CW are connected in series with Armature winding

The armature of a dc machine is laminated to reduce: (A) Eddy current loss (B) Hysteresis loss (C) copper losses (D) friction and windage losses

Description : The armature of a dc machine is laminated to reduce: (A) Eddy current loss (B) Hysteresis loss (C) copper losses (D) friction and windage losses

Last Answer : Ans: A Thinner the laminations, greater is the resistance offered to the induced e.m.f., smaller the current and hence lesser the I2R loss in the core.

A commutator in a d.c. machine (A) Reduces power loss in armature. (B) Reduces power loss in field circuit. (C) Converts the induced a.c armature voltage into direct voltage. (D) Is not necessary.

Description : A commutator in a d.c. machine (A) Reduces power loss in armature. (B) Reduces power loss in field circuit. (C) Converts the induced a.c armature voltage into direct voltage. (D) Is not necessary.

Last Answer : Ans: C As name suggests, it commutes ac into dc.

In a d.c. machine, the armature mmf is (A) stationary w.r.t. armature. (B) rotating w.r.t. field. (C) stationary w.r.t. field. (D) rotating w.r.t. brushes.

Description : In a d.c. machine, the armature mmf is (A) stationary w.r.t. armature. (B) rotating w.r.t. field. (C) stationary w.r.t. field. (D) rotating w.r.t. brushes.

Last Answer : (C) stationary w.r.t. field.

The laminations of the armature of a D.C. machine are usually _____ thick. (a) 0.1 to 0.2 mm (b) 0.2 to 0.3 mm (c) 0.3 to 0.4 mm (d) 0.4 to 0.5 mm

Description : The laminations of the armature of a D.C. machine are usually _____ thick. (a) 0.1 to 0.2 mm (b) 0.2 to 0.3 mm (c) 0.3 to 0.4 mm (d) 0.4 to 0.5 mm

Last Answer : (d) 0.4 to 0.5 mm

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.

State functions of the armature core in DC machine and name material used for armature core.

Last Answer : Functions of armature core: 1) Support the armature winding which is placed in its slots. 2) Rotate as driven by the prime mover (generator) or as per the torque produced (motor).  Hence ... magnetic path to increase the magnitude of induced emf for a certain MMF created by the field winding. 

Which of the following quantity maintains the same direction whether a D.C. machine runs as a generator or as a motor a. Induced e.m.f. b. Armature Current c. Field Current d. Supply Current

Description : Which of the following quantity maintains the same direction whether a D.C. machine runs as a generator or as a motor a. Induced e.m.f. b. Armature Current c. Field Current d. Supply Current  

Last Answer : Which of the following quantity maintains the same direction whether a D.C. machine runs as a generator or as a motor a. Induced e.m.f. b. Armature Current c. Field Current d. Supply Current  

The number of parallel paths in armature winding of four pole wave winding connected dc machine having...

Description : The number of parallel paths in armature winding of four pole wave winding connected dc machine having 22 coil sides is (1) 4 (2) 22 (3) 2 (4) 11 

Last Answer : Ans- Option (3) because wave winding always have 2 parallel paths

The number of parallel paths in the armature winding of a 4 -pole, wave connected d.c. machine having 28 coilside is : -

Description :  The number of parallel paths in the armature winding of a 4 -pole, wave connected d.c. machine having 28 coilside is : -  a) 28 b) 14 c) 4 d) 2

Last Answer : 2

A 220 V dc machine has an armature resistance o f 1-ohm. If the full load current is 20A, the difference...

Description : A 220 V dc machine has an armature resistance o f 1-ohm. If the full load current is 20A, the difference in the induced voltage when the machine is running as a motor, and as a generator is

Last Answer : A 220 V dc machine has an armature resistance o f 1-ohm. If the full load current is 20A, the difference in the induced voltage when the machine is running as a motor, and as a generator is 40 V.

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

Last 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.

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

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

UNIT 1 fundamentals of AC rotating machine

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

Last 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.

Equalizer rings are used in a dc machine to

Description : Equalizer rings are used in a dc machine to (A) provide mechanical balance (B) balance the flux produced by the poles (C) provide path for the circulating currents (D) overcome armature reaction 

Last Answer : Equaliser rings in dc machine is     Current flowing in machines to share equally during parcel operation of dc machines    In case of Equaliser rings are not connected to machine the load ... between two machines flowing not equally     Equaliser rings are use series and compound motors only

A 4-pole, 3-phase, double-layer winding is housed in a 36-slot stator for an ac machine with

Description : A 4-pole, 3-phase, double-layer winding is housed in a 36-slot stator for an ac machine with 60o phase spread. Coil span is 7 short pitches. Number of slots in which top and bottom layers belong to different phases is  (A) 24 (B) 18 (C) 12 (D) 0

Last Answer : A 4-pole, 3-phase, double-layer winding is housed in a 36-slot stator for an ac machine with 60o phase spread. Coil span is 7 short pitches. Number of slots in which top and bottom layers belong to different phases is 24 

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