Describe the reason of using dc series motor for electric trains.
Last 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
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142 views
1 answer
asked
Sep 18, 2018
by
anonymous
A 200 V dc motor takes a field current of 2 A to generate a back emf of 180 V. If the field winding resistance is 80 Ω, the resistance of the shunt field regulator is (A) 10 Ω (B) 20 Ω (C) 100 Ω (D) 180 Ω
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77 views
0 answers
asked
Jun 4, 2018
by
anonymous
As the speed increases, the torque developed by a dc servo motor (A) decrease with a negative slope (B) increases with a positive slope (C) remain constant (D) becomes unstable
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69 views
0 answers
asked
Jun 4, 2018
by
anonymous
Regenerative breaking of ac-dc converter fed dc motor is possible when firing delay angle of SCRs is (A) 30° (B) 60° (C ) 90° (D) 120°
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64 views
0 answers
asked
Jun 4, 2018
by
anonymous
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%
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502 views
1 answer
asked
May 17, 2018
by
anonymous
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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
Last 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
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489 views
1 answer
asked
May 8, 2018
by
anonymous
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
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343 views
1 answer
asked
May 3, 2018
by
anonymous
In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is :
Last Answer : In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is : 0.075
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112 views
1 answer
asked
Apr 29, 2018
by
anonymous
The function of a brush and commutator arrangement in a dc motor is to (1) produce unidirectional torque (2) produce unidirectional current in the armature (3) help in changing the direction of rotation of the armature (4) reduce sparking
Last Answer : The function of a brush and commutator arrangement in a dc motor is to produce unidirectional torque
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2.5k views
1 answer
asked
Apr 29, 2018
by
anonymous
What is the RPM of a DC motor?
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69 views
0 answers
asked
Mar 15, 2018
by
anonymous
What are the speed control methods of dc motor?
Last Answer : Field control of DC motor Armature control of DC motor
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263 views
2 answers
asked
Dec 16, 2017
by
anonymous
Last Answer : Induction motor is a AC motor it is also known as asynchronous motor .
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101 views
1 answer
asked
Sep 9, 2017
by
anonymous
Armature control of DC motor
Last Answer : Armature control of DC motor
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162 views
2 answers
asked
Aug 9, 2017
by
anonymous
Field control of DC motor
Last Answer : Field control of DC motor
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126 views
2 answers
asked
Aug 9, 2017
by
anonymous
Separately Excited DC motor
Last Answer : Separately Excited DC motor
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360 views
2 answers
asked
Aug 9, 2017
by
anonymous
Four Quadrant Operation Of DC Motor
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226 views
0 answers
asked
Aug 9, 2017
by
anonymous
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Types of three phase induction motor rotor
Last Answer : Types of three phase induction motor rotorSquirrel cage rotor : There are two types of three phase induction motor rotor one is squirrel cage rotor and second is wound rotor. About 80 to ... control of three phase induction motor via rotor resistance control method is possible with this rotor.
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148 views
1 answer
asked
Aug 9, 2017
by
anonymous
In a 6-pole wave wound dc machine the number of conductors is 70. The back pitch and commutator segments, respectively, are (A) 11and 35 (B) 12 and 34 (C) 13 and 35 (D) 14 and 34
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101 views
0 answers
asked
Jun 4, 2018
by
anonymous
The number of brushes in a 6-pole double-layer lap wound dc machine is (A) 8 (B) 6 (C) 4 (D) 2
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154 views
0 answers
asked
Jun 4, 2018
by
anonymous
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
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955 views
1 answer
asked
Jun 4, 2018
by
anonymous
The demagnetizing AT/pole of a 4-pole dc generator is 480. The number of conductors is 480 and the current in each conductor is 40 A. Then the required brush shift in mechanical degrees (A) 9° (B) 7° (C) 5° (D) 3°
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69 views
0 answers
asked
Jun 4, 2018
by
anonymous
In a dc shunt generator critical field circuit resistance line is the line drawn (A) above the OCC (B) below the OCC (C) tangent to the saturation curve (D) tangent to the linear portion of OCC
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113 views
0 answers
asked
Jun 4, 2018
by
anonymous
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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
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127 views
1 answer
asked
May 8, 2018
by
anonymous
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
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595 views
1 answer
asked
May 3, 2018
by
anonymous
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
Last Answer : It can be corrected by increasing the input to the prime mover.
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364 views
2 answers
asked
May 1, 2018
by
anonymous
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
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298 views
2 answers
asked
May 1, 2018
by
anonymous
Identify the increasing order of voltage regulation of the following dc generators a same load : (A) differential compound, shunt and under compound (B) shunt, differential compound and ... C) under compound, shunt and differential compound (D) shunt, under compound and differential compound
Last Answer : Identify the increasing order of voltage regulation of the following dc generators a same load : under compound, shunt and differential compound
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130 views
1 answer
asked
Apr 30, 2018
by
anonymous
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.
Last 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.
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127 views
1 answer
asked
Apr 29, 2018
by
anonymous
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
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378 views
1 answer
asked
Apr 29, 2018
by
anonymous
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
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621 views
1 answer
asked
Apr 29, 2018
by
anonymous
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
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182 views
1 answer
asked
Apr 29, 2018
by
anonymous
What is the difference between an AC and DC generator?
Last Answer : The generator which generates DC voltage is called DC generator and generator which generates AC voltage is called AC generator (or) Alternator. In DC generator armature is rotated and field winding ... generator. A DC generator can generate low voltages but an AC generator can generate upto 11kv.
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319 views
1 answer
asked
Mar 15, 2018
by
anonymous
What is the principle of DC generator?
Last Answer : principle
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81 views
1 answer
asked
Mar 15, 2018
by
anonymous
Brushes of DC machine are made up of ?
Last Answer : Brushes of DC machine are made up of carbon.
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165 views
1 answer
asked
Mar 3, 2018
by
anonymous
From which material field coils of DC generator are made of?
Last Answer : Field coils of DC generator are usually made of copper.
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118 views
1 answer
asked
Mar 3, 2018
by
anonymous
Why is the armature of DC generator laminated?
Last Answer : The armature of DC generator is laminated to reduce eddy current losses.
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176 views
1 answer
asked
Mar 3, 2018
by
anonymous
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In DC generators lamination core are generally made of?
Last Answer : In DC generators lamination core are generally made of silicon steel.
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264 views
1 answer
asked
Mar 3, 2018
by
anonymous
Last Answer : Ac motor required AC power supply while DC motor required DC power supply. AC motor do not have commutator and DC motor have commutator. Speed of Ac motor can be varied by ... or three phase but DC motor can only be single phase.
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83 views
1 answer
asked
Jan 8, 2018
by
Nani
The heating time constant of a totally enclosed motor is relatively Select one: a. higher b. lower c. independent of type of enclosure. d. small .
Last Answer : B
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301 views
1 answer
asked
Jul 2, 2020
by
medo
The efficiency of a 3-phase, star connected synchronous motor is 95% and it takes 24A at full load and unity power factor. What will be the induced e.m.f. if total mechanical power developed at full load and 0.9 power factor leading is 14620W. The synchronous impedance per phase is (0.2+j2) Ω.
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180 views
0 answers
Split phase induction motor
Last Answer : Split phase induction motor : There are two windings used in split phase induction motor. It is a type of single-phase induction motor. There are two winding one is called main winding and ... motor have low starting torque it is used for small fans, blowers, centrifugal pumps, grinders etc.
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233 views
1 answer
asked
Sep 20, 2018
by
anonymous
Which motor is generally used in Tap Recorders? A) universal motor B) reluctance motor C) split phase motor D) hysteresis motor
Last Answer : Which motor is generally used in Tap Recorders? A) universal motor B) reluctance motor C) split phase motor D) hysteresis motor
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71 views
1 answer
asked
Jun 17, 2018
by
anonymous
The starting torque of a V/f controlled inverter-fed 3-phase induction motor operating at 25 Hz as compared with the same motor operating at 50 Hz is (A) more (B) double (C) equal (D) less
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62 views
0 answers
asked
Jun 4, 2018
by
anonymous
In slip-energy recovery scheme of converter-fed 3-phase induction motor, super synchronous speeds are possible by (A) injecting voltage into the stator (B) injecting voltage into the rotor (C) extracting voltage from the stator (D) extracting voltage from the rotor.
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70 views
0 answers
asked
Jun 4, 2018
by
anonymous
Fast acceleration and high-speed cruising electric traction drive motor is (A) separately excited dc motor (B) DC series motor (C) AC series motor (D) 3-phase squirrel cage induction motor
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72 views
0 answers
asked
Jun 4, 2018
by
anonymous
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As compared to a split phase motor, a capacitor start motor has _____.
Last Answer : As compared to a split phase motor, a capacitor start motor has higher starting torque.
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147 views
1 answer
asked
May 29, 2018
by
anonymous
For very low speed and high power applications the best suited ac motor is:
Last Answer : For very low speed and high power applications the best suited ac motor is: synchronous motor
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139 views
1 answer
asked
May 22, 2018
by
anonymous
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
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1.2k views
1 answer
asked
May 22, 2018
by
anonymous
For a 1.8o, 2-phase bipolar stepper motor, the stepping rate is 100 steps/second. The rotational speed of the motor in rpm is (A) 15 (B) 30 (C) 60 (D) 90
Last Answer : For a 1.8o, 2-phase bipolar stepper motor, the stepping rate is 100 steps/second. The rotational speed of the motor in rpm is 30
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505 views
1 answer
asked
May 17, 2018
by
anonymous
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The following motor definitely has a permanent magnet rotor (A) DC commutator motor (B) Brushless dc motor (C) Stepper motor (D) Reluctance motor
Last Answer : The following motor definitely has a permanent magnet rotor Stepper motor
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304 views
1 answer
asked
May 17, 2018
by
anonymous
