Separately Excited DC motor
Last Answer : Separately Excited DC motor
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Aug 9, 2017
by
anonymous
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286 views
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Oct 14, 2020
by
anonymous
separately excited dc motor controlled by chopper with a frequency of 500hz and source voltage of 230v and rated value of motor is 220v 24A 100 rpm find its duty ratio at 1.2 times rated torgue and 500rpm
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A separately excited d.c. motor fed from single phase full converter with firing angle 60° runs at 1000 r.p.m. If motor is connected to single phase semiconverter with the same firing angle of 60°, it would run at (a) 2000 rpm (b) 1850 rpm (c) 1500 rpm (d) 1000 rpm
Last Answer : Ans =1500
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1.4k views
3 answers
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May 25, 2018
by
anonymous
A single-phase half-controlled rectifier is driving a separately excited dc motor. The dc motor has a back emf constant of 0.5 V/rpm. The armature current is 5 A without any ripple. The armature resistance is 2 Ohm. The ... of the motor will be (A) 339 rpm (B) 359 rpm (C) 366 rpm (D) 386 rpm
Last Answer : 359
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1.1k views
1 answer
asked
May 18, 2018
by
anonymous
A DC chopper is used for regenerative braking of a separately excited DC motor. The DC supply voltage is 400V. The armature current during regenerative braking is kept constant at 300 A with negligible ripple. For a duty cycle of 60% ... to the DC supply is (a) 78 kW (b) 58 kW (c) 38 kW (d) 48 kW
Last Answer : 48
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430 views
2 answers
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May 13, 2018
by
anonymous
A separately excited dc motor operating in first quadrant is fed from 3-phase semi -converter free -wheeling diode is open circuited, then the motor : (A) can be operated in first quadrant (B) ... in first & second quadrants (C) can be operated in first & fourth quadrants (D) cannot be operated
Last Answer : A separately excited dc motor operating in first quadrant is fed from 3-phase semi -converter free -wheeling diode is open circuited, then the motor : can be operated in first & fourth quadrants
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1 answer
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Apr 30, 2018
by
anonymous
The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a firing delay angle, α and flux, Φ (A) directly proportional to α and Φ (B) ... proportional to α and inversely proportional to Φ (D) directly proportional to Φ and inversely proportional to α
Last Answer : The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a firing delay angle, α and flux, Φ directly proportional to α and inversely proportional to Φ
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1 answer
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Apr 28, 2018
by
anonymous
A separately excited dc motor is required to be controlled, from a 3-phase supply, for its operation in the first quadrant only. The most preferred converter would be (a) 3-phase fully controlled ... converter with free wheel diode (c) 3-phase dual converter (d) 3-phase half wave converter
Last Answer : A
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1 answer
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Apr 10, 2018
by
anonymous
What is the difference between self-excited and separately excited DC generator?
Last Answer : Self-excited generator: In a self-excited generator the field winding is excited by an external DC source like a battery etc. Separately excited generator: In a separately excited generator the field poles ... is again fed to the field winding and goes on till the generator builds up voltage.
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A separately excited generator as compared to a self-excited generator (a) is amenable to better voltage con-trol (b) is more stable (c) has exciting current independent of load current (d) has all above features
Last Answer : Ans: d
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A separately excited d.c. machine is coupled to a 50 Hz, three-phase, 4-pole induction machine as shown in the figure. The Dc machine is energized first and the machines rotate at 1 600 ... three phase source, the phase sequence being consistent with the direction of rotation. In steady state
Last Answer : A separately excited d.c. machine is coupled to a 50 Hz, three-phase, 4-pole induction machine as shown in the figure. The Dc machine is energized first and the machines rotate at 1 600 1pm. ... rotation. In steady state DC machine acts as a motor and the induction machine acts as a generator
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1 answer
asked
May 20, 2018
by
anonymous
The supply both to field and armature circuits are disconnected simultaneously in a separately excited dc motor and it comes to a standstill in 5 sec. If the armature circuit of this motor is disconnected from supply with field ... rest in (1) 5 sec (2) 7 sec (3) 4 sec (4) A very long time
Last Answer : 5 sec only.standstill time doesn't depend upon field excitation
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1 answer
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Apr 11, 2018
by
anonymous
A separately excited dc generator is running at rated speed and at no load. If its field winding is suddenly connected to a dc source then rise in armature generated voltage is governed by (1) Armature time constant (2) Field time constant (3) Both (a) and (b) (4) Mechanical time constant
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asked
Apr 11, 2018
by
anonymous
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Last Answer : In a separately excited generator supplying rated load the armature reaction is always present.
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138 views
1 answer
asked
Mar 21, 2018
by
anonymous
Last Answer : A separately excited generator as compared to a self-excited generator is amenable to better voltage control, more stable, has exciting current independent of load current.
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1 answer
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Mar 20, 2018
by
anonymous
The basic type of D.C. motor speed control where a generator armature directly feeds the motor armature and the motor and generator fields are excited by a separate D.C. source is called ___________________. A. Burmeister-Wain B. Ward-Leonard C. Sperry-Rand D. Atlas-Copco
Last Answer : Answer: B
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1 answer
On some diesel-electric ships, the DC propulsion motor will only attain half speed when the generator fields are fully excited. Speeds above this are obtained by _____________. A. rotating brush ... B. raising the generator engine speed C. lowering the generator engine speed D. decreasing excitation
Last Answer : Answer: B
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1 answer
An a.c. tachometer is just a ________with one phase excited from the carrier frequency. (A) two-phase A.C. servomotor (B) two-phase induction motor (C) A.C. operated universal motor (D) hybrid stepper motor.
Last Answer : Ans: D This is a special purpose machine whose stator coil can be energized by electronically switched current.
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1 answer
The stator of a 415V, 50 Hz, 4-pole slip ring Induction Motor is excited by rated frequency with slip rings open circuited. The rotor is made to rotate at a speed of 600 rpm in the opposite direction to the ... frequency of induced voltage across slip ring is A) 30 Hz B) 70 Hz C) 20 Hz D) 35 Hz
Last Answer : The stator of a 415V, 50 Hz, 4-pole slip ring Induction Motor is excited by rated frequency with slip rings open circuited. The rotor is made to rotate at a speed of 600 rpm in the opposite direction to the normal direction, The frequency of induced voltage across slip ring is 70 Hz
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1 answer
asked
Jun 17, 2018
by
anonymous
A single-phase induction motor with only the main winding excited would exhibit the following response at synchronous speed (A) Rotor current is zero (B) Rotor current is non-zero and is ... and backward rotating fields are equal (D) Forward rotating field is more than the backward rotating field
Last Answer : A single-phase induction motor with only the main winding excited would exhibit the following response at synchronous speed (A) Rotor current is zero (B) Rotor current is non-zero and is ... backward rotating fields are equal (D) Forward rotating field is more than the backward rotating field
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1 answer
asked
May 18, 2018
by
anonymous
A 0.5 Hp, 6 pole wound rotor induction motor is excited by a 3 phase 60 Hz source. Calculate the frequency of the rotor current at standstill. (A) 50 Hz (B) 30 Hz (C) 60 Hz (D) 120 Hz
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Apr 5, 2018
by
anonymous
Last Answer : An over excited synchronous motor on noload is known as synchronous condenser.
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1 answer
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Mar 20, 2018
by
anonymous
If the load of the normally excited synchronous motor is increased the power factor will?
Last Answer : If the load of the normally excited synchronous motor is increased the power factor will become lagging.
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1 answer
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Mar 18, 2018
by
anonymous
If the field of synchronous motor is under excited, power factor will be?
Last Answer : If the field of synchronous motor is under excited, power factor will be lagging.
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1 answer
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Mar 18, 2018
by
anonymous
Last Answer : Self excited Dc motor have same source of power to armature and field winding
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1 answer
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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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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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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1 answer
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Sep 20, 2018
by
anonymous
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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1 answer
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Sep 18, 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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1 answer
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Jun 17, 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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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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Jun 4, 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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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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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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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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Jun 4, 2018
by
anonymous
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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1 answer
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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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1 answer
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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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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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1 answer
asked
May 17, 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
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
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A 400 V, 50 Hz 30 hp, three-phase induction motor is drawing 50 A current at 0.8 power factor lagging. The stator and rotor copper losses are 1.5 kW and 900 W respectively. The friction and windage losses are 1050 W and the ... the motor will be (A) 23.06 kW (B) 24.11 kW (C) 25.01 kW (D) 26.21 kW
Last Answer : A 400 V, 50 Hz 30 hp, three-phase induction motor is drawing 50 A current at 0.8 power factor lagging. The stator and rotor copper losses are 1.5 kW and 900 W respectively. The friction and windage losses are 1050 W and the core losses are 1200 W. The air-gap power of the motor will be 25.01 kW
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363 views
1 answer
asked
May 17, 2018
by
anonymous
In a stepper motor, the detent torque means (A) minimum of the static torque with the phase winding excited (B) maximum of the static torque with the phase winding excited (C) minimum of ... torque with the phase winding unexcited (D) maximum of the static torque with the phase winding unexcited
Last Answer : In a stepper motor, the detent torque means maximum of the static torque with the phase winding unexcited
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752 views
1 answer
asked
May 17, 2018
by
anonymous
The locked rotor current in a 3-phase, star connected 15 , kW 4 , pole 230 V , 50 Hz induction motor at rated conditions is 50 A. Neglecting losses and magnetizing current, the approximate locked rotor line current drawn when the motor ... Hz supply is (A) 58.5 A (B) 45.0 A (C) 42.7 A (D) 55.6 A
Last Answer : The locked rotor current in a 3-phase, star connected 15 , kW 4 , pole 230 V , 50 Hz induction motor at rated conditions is 50 A. Neglecting losses and magnetizing current, the approximate locked rotor line current drawn when the motor is connected to a 236 , V 57 Hz supply is 45.0 A
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458 views
1 answer
asked
May 17, 2018
by
anonymous
In case of split phase motor, the phase shift between currents in the two windings is around A) 30° B) 70° C) 90° D) 120°
Last Answer : In case of split phase motor, the phase shift between currents in the two windings is around 30°
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200 views
1 answer
asked
May 17, 2018
by
anonymous
Which type of motor is most suitable for computerprinter drive? A) Reluctance motor B) Hysteresis motor C) Shaded pole motor D) Stepper motor
Last Answer : Stepper motor type of motor is most suitable for computer printer drive?.
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173 views
1 answer
asked
May 17, 2018
by
anonymous
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The torque speed characteristic of a repulsion motor resembles which of the following d.c. motor characteristics A) Separately excited B) Shunt C) Series D) Compound
Last Answer : The torque speed characteristic of a repulsion motor resembles which of the following d.c. motor characteristics Series
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590 views
1 answer
asked
May 17, 2018
by
anonymous
In a Synchronous motor, the magnitude of stator back e.m.f (Eb) depends on
Last Answer : In a Synchronous motor, the magnitude of stator back e.m.f (Eb) depends on DC excitation only
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174 views
1 answer
asked
May 15, 2018
by
anonymous
