Induction generator is self excited machine. a) True b) False

 Induction generator is self excited machine. a) True b) False
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What is the difference between self-excited and separately excited DC generator?

Description : 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. 

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

Description : 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

for the voltage built-up a self-excited D.C. generator, which of the following is not an essential

Description : for the voltage built-up a self-excited D.C. generator, which of the following is not an essential condition.  1.there must be some residual flux  2.field winding mmf must aid the residual ... 3.total field circuit resistance must be less than t critical value  4.armature speed must be very high

Last Answer : for the voltage built-up a self-excited D.C. generator, which of the following is not an essential condition.  1.there must be some residual flux  2.field winding mmf must aid the ... .total field circuit resistance must be less than t critical value  4.armature speed must be very high

The slight curvature at the lower end of the O.C.C. of a self-excited dc generator is due to

Description : The slight curvature at the lower end of the O.C.C. of a self-excited dc generator is due to  1. residual pole flux 2. high armature speed 3.magnetic inertia 4. high field circuit resistance

Last Answer : The slight curvature at the lower end of the O.C.C. of a self-excited dc generator is due to magnetic inertia

A separately excited generator as compared to a self-excited generator?

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.

A separately excited d.c. machine is coupled to a 50 Hz, three-phase, 4-pole induction machine as shown in

Description : 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  

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.

Description : 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.

As shown in the illustration, the generator field is excited with DC current provided by ____________. EL-0016 A. conductors '1', '2' and '3' B. inductor 'L1' C. rectifier 'CR1' D. winding 'S-2'

Description : As shown in the illustration, the generator field is excited with DC current provided by ____________. EL-0016 A. conductors '1', '2' and '3' B. inductor 'L1' C. rectifier 'CR1' D. winding 'S-2'

Last Answer : Answer: C

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

Description : 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

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 alignment B. raising the generator engine speed C. lowering the generator engine speed D. decreasing excitation

Description : 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

Which statement is true concerning a split-phase induction motor? A. Motor rotation can be reversed without changing the windings or leads. B. Motor speed can be readily adjusted from zero to full speed. C. The motor will run as a generator with the proper wiring. D. Motor rotation can be reversed by reversing the leads on the starting winding.

Description : Which statement is true concerning a split-phase induction motor? A. Motor rotation can be reversed without changing the windings or leads. B. Motor speed can be readily adjusted from zero to full ... proper wiring. D. Motor rotation can be reversed by reversing the leads on the starting winding.

Last Answer : Answer: D

A transformer works on the principle of – (1) Self induction (2) Mutual induction (3) Generator (4) Inverter

Description : A transformer works on the principle of – (1) Self induction (2) Mutual induction (3) Generator (4) Inverter

Last Answer : (2) Mutual induction

The principle of AC generator is: a. Mutual induction b. self induction c. electromagnetic induction d. Induction

Description : The principle of AC generator is: a. Mutual induction b. self induction c. electromagnetic induction d. Induction

Last Answer : b. self induction

A transformer works on the principle of (1) Self induction (2) Mutual induction (3) Generator (4) Inverter

Description : A transformer works on the principle of (1) Self induction (2) Mutual induction (3) Generator (4) Inverter

Last Answer : Mutual induction

Voltage build up in an isolated induction generator depends on A. Capacitor bank value B. Residual magnetism of the rotor iron C. Residual magnetism of the stator iron a) A, B b) A, B, C c) B d) A, C

Description : Voltage build up in an isolated induction generator depends on A. Capacitor bank value B. Residual magnetism of the rotor iron C. Residual magnetism of the stator iron a) A, B b) A, B, C c) B d) A, C

Last Answer : Ans: A

If the residual flux is absent in the rotor iron of the isolated induction generator, a) it will not run. b) it will run as induction motor c) it will burn the winding d) it will not affect the characteristic of the generator

Description : If the residual flux is absent in the rotor iron of the isolated induction generator, a) it will not run. b) it will run as induction motor c) it will burn the winding d) it will not affect the characteristic of the generator

Last Answer : Ans: A

Induction generator a) can not work in isolation b) can work in isolation c) should work in parallel with synchronous generators d) any of the mentioned

Description : Induction generator a) can not work in isolation b) can work in isolation c) should work in parallel with synchronous generators d) any of the mentioned

Last Answer : Ans: C

When TG works as induction generator?

Description : When TG works as induction generator?

Last Answer : When excitation alone lost.  

A transformer works on the basic principle of ____________. A. self impedance B. attraction and repulsion C. mutual induction D. increasing power

Description : A transformer works on the basic principle of ____________. A. self impedance B. attraction and repulsion C. mutual induction D. increasing power

Last Answer : Answer: C

What are methods available for making single phase induction motor a self starting?

Description : What are methods available for making single phase induction motor a self starting?

Last Answer : By slitting the single phase, by providing shading coil in the poles.

Why single phase induction motor is not a self starting one?

Description : Why single phase induction motor is not a self starting one?

Last Answer : When motor fed supply from single phase, its stator winding produces an alternating flux, which doesn’t develop any torque.

What are the use of mutual induction and self-induction?

Description : What are the use of mutual induction and self-induction?  

Last Answer : Use of mutual induction a. Transformers are works on this principle. b. An inductance furnace makes use of it. c. Used in ignition coils of motor car, motor cycles, scooters etc. Use of ... 's normal working time. c. Used in welding plant rectifiers to keep arc stationary by smoothing choke. 

The stator of a 415V, 50 Hz, 4-pole slip ring Induction Motor is excited by rated frequency with slip rings open

Description : 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

A single-phase induction motor with only the main winding excited would exhibit the following response at

Description : 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

In a separately excited generator supplying rated load the armature reaction?

Last Answer : In a separately excited generator supplying rated load the armature reaction is always present.

The difference between the synchronous speed of an induction machine and its operating speed (slip) may be correctly expressed _____________. A. as a percent of synchronous speed B. as a decimal fraction of synchronous speed C. directly in revolutions per minute D. as all of the above

Description : The difference between the synchronous speed of an induction machine and its operating speed (slip) may be correctly expressed _____________. A. as a percent of synchronous speed B. as a decimal fraction of synchronous speed C. directly in revolutions per minute D. as all of the above

Last Answer : Answer: A

A three-phase, induction-type motor experiences an open in one phase. Which of the listed automatic protective devices will prevent the machine from being damaged? A. Overspeed trip B. Thermal overload relay C. Three-pole safety switch D. Magnetic blowout coil

Description : A three-phase, induction-type motor experiences an open in one phase. Which of the listed automatic protective devices will prevent the machine from being damaged? A. Overspeed trip B. Thermal overload relay C. Three-pole safety switch D. Magnetic blowout coil

Last Answer : Answer: B

The purpose of a cage rotor winding placed on the rotor of a synchronous motor is to _____________. A. provide excitation to the DC field B. start the machine as an induction motor C. contribute extra torque at synchronous speed D. prevent the machine from falling out of step

Description : The purpose of a cage rotor winding placed on the rotor of a synchronous motor is to _____________. A. provide excitation to the DC field B. start the machine as an induction motor C. contribute extra torque at synchronous speed D. prevent the machine from falling out of step

Last Answer : Answer: B

There Are A transformer And An Induction Machine. Those Two Have The Same Supply. For Which Device The Load Current Will Be Maximum? And Why?

Description : There Are A transformer And An Induction Machine. Those Two Have The Same Supply. For Which Device The Load Current Will Be Maximum? And Why?

Last Answer : The motor has max load current compare to that of trformer because the motor consumes real power.. and the trformer is only producing the working flux and its not consuming.. hence the load current in the trformer is because of core loss so it is minimum.

Name the tests to be conducted for predetermining the performance of 3-phase induction machine.

Description : Name the tests to be conducted for predetermining the performance of 3-phase induction machine.

Last Answer : (a) No load test (b) Blocked rotor test

In an induction machine, if the air gap increased a) Speed will be reduced b) Efficiency will be improved c) Power factor will be lowered d) Breakdown torque will be reduced

Description : In an induction machine, if the air gap increased a) Speed will be reduced b) Efficiency will be improved c) Power factor will be lowered d) Breakdown torque will be reduced

Last Answer : Ans: Power factor will be lowered

A 400kW, 3-phase, 440V, 50Hz induction motor has a speed of 950 r.p.m. on fullload. The machine has 6 poles. The slip of the machine will be _______________. (A) 0.06 (B) 0.10 (C) 0.04 (D) 0.05

Description : A 400kW, 3-phase, 440V, 50Hz induction motor has a speed of 950 r.p.m. on fullload. The machine has 6 poles. The slip of the machine will be _______________. (A) 0.06 (B) 0.10 (C) 0.04 (D) 0.05

Last Answer : Ans: D N = Ns (1-S) 950 = 120 x 50 (1-S)/6 S = 0.05

Slip of the induction machine is 0.02 and the stator supply frequency is 50 Hz. What will be the frequency of the rotor induced emf? (A) 10 Hz. (B) 50 Hz. (C) 1 Hz. (D) 2500 Hz.

Description : Slip of the induction machine is 0.02 and the stator supply frequency is 50 Hz. What will be the frequency of the rotor induced emf? (A) 10 Hz. (B) 50 Hz. (C) 1 Hz. (D) 2500 Hz.

Last Answer : Ans: C Given : s = 0.02 ; f = 50 Hz Therefore, frequency of rotor induced emf = s f = 0.02 x 50 = 1.0 Hz

The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a (A) dc machine. (B) 3 phase induction machine. (C) synchronous machine. (D) single phase induction machine.

Description : The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a (A) dc machine. (B) 3 phase induction machine. (C) synchronous machine. (D) single phase induction machine.

Last Answer : Ans: all options are correct

The main purpose of an electric space heater installed in a large AC generator is to _____________. A. keep the lube oil warm for quick starting B. prevent moisture from condensing in the windings when the machine is shutdown C. prevent the windings from becoming brittle D. prevent acidic pitting of the slip rings

Description : The main purpose of an electric space heater installed in a large AC generator is to _____________. A. keep the lube oil warm for quick starting B. prevent moisture from condensing in the ... is shutdown C. prevent the windings from becoming brittle D. prevent acidic pitting of the slip rings

Last Answer : Answer: B

Two paralleled alternators are operating near rated load. If one trips out mechanically, which of the listed actions should be taken FIRST? A. Restart the tripped machine immediately. B. Strip the board of all non-vital circuits. C. Start the emergency generator. D. Transfer all vital loads to the emergency bus.

Description : Two paralleled alternators are operating near rated load. If one trips out mechanically, which of the listed actions should be taken FIRST? A. Restart the tripped machine immediately. B. Strip the board ... circuits. C. Start the emergency generator. D. Transfer all vital loads to the emergency bus.

Last Answer : Answer: B

When paralleling two AC generators, the frequency of the machine coming online, immediately prior to closing its breaker, should be ____________. A. slightly less than the oncoming generator frequency B. the same as the bus frequency C. slightly greater than the bus frequency D. the same as the bus voltage

Description : When paralleling two AC generators, the frequency of the machine coming online, immediately prior to closing its breaker, should be ____________. A. slightly less than the oncoming generator frequency B. the ... bus frequency C. slightly greater than the bus frequency D. the same as the bus voltage

Last Answer : Answer: C

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

A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A from 220V supply. The speed of the machine as a motor will be (A) 800 rpm. (B) more than 800 rpm. (C) less than 800 rpm. (D) both higher or lower than 800 rpm.

Description : A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A from 220V supply. The speed of ... . (B) more than 800 rpm. (C) less than 800 rpm. (D) both higher or lower than 800 rpm.

Last Answer : (C) less than 800 rpm.

What's is the self excited dc motor?

Last Answer : Self excited Dc motor have same source of power to armature and field winding

Why synchronous machine is called doubly excited machine?

Description : Why synchronous machine is called doubly excited machine?

Last Answer : Armature windings of synchronous machines either deliver 3 phase AC or absorb 3 phase AC source,  whereas field windings are energized from DC source. Thus due to presence of AC on armature and DC on field windings, synchronous machines are often referred as doubly excited machines.

Labelling on the induction motor is voluntary A. True B. False

Description : Labelling on the induction motor is voluntary A. True B. False

Last Answer : true

The torque and current curves for a three-phase induction motor with a cage rotor, are shown in the illustration. Which of the following statements is true concerning the depicted curves? EL-0056 A. As slip increases, rotor reactance decreases. B. The pullout point on the torque curve is about seven times the normal full load torque value. C. At stand still, stator current is 150% of normal. D. If the motor is loaded to the point where 40% slip has resulted, it will stall.

Description : The torque and current curves for a three-phase induction motor with a cage rotor, are shown in the illustration. Which of the following statements is true concerning the depicted curves? EL-0056 A. As slip ... D. If the motor is loaded to the point where 40% slip has resulted, it will stall.

Last Answer : Answer: D

Which of the following statements is true concerning a polyphase synchronous propulsion motor? A. The motor is started as an induction motor. B. Resistance is gradually added to the rotor circuit. C. The starting current is held below the rated current. D. The field winding is energized for starting purposes only.

Description : Which of the following statements is true concerning a polyphase synchronous propulsion motor? A. The motor is started as an induction motor. B. Resistance is gradually added to the rotor circuit. C. ... is held below the rated current. D. The field winding is energized for starting purposes only.

Last Answer : Answer: A

Corona discharge is related to the operation of a/an (A) Induction motor (B) Electrostatic precipitator (C) Fast breeder reactor (D) Magneto hydrodynamic generator (MHD)

Description : Corona discharge is related to the operation of a/an (A) Induction motor (B) Electrostatic precipitator (C) Fast breeder reactor (D) Magneto hydrodynamic generator (MHD)

Last Answer : Option B

Which one of the following laws best describes the operation of an electric generator? w) Ampere's Law x) Gauss' Law y) Ohm's Law for Conductors z) Faraday's Law of Induction

Description : Which one of the following laws best describes the operation of an electric generator? w) Ampere's Law x) Gauss' Law y) Ohm's Law for Conductors z) Faraday's Law of Induction

Last Answer : ANSWER: Z -- FARADAY'S LAW OF INDUCTION 

With a neat diagram explain doubly fed induction generator (DFIG).

Description : With a neat diagram explain doubly fed induction generator (DFIG). 

Last Answer : Diagram of Doubly fed induction generator (DFIG):  Explanation :-  DFIG can feed power through the stator as well as rotor to the grid. The stator is directly connected to the fixed frequency ... voltage is 690 V AC. So it must be step up to 33 KV to connect to power grid.  

Explain Squirrel Cage Induction Generator (SCIG) and also draw a diagram.

Description : Explain Squirrel Cage Induction Generator (SCIG) and also draw a diagram. 

Last Answer : Explanation (Operation):- In this system gearbox is used to increase the speed of high speed shaft as per design. IG require reactive power for excitation. Rotor of SCIG is ... , variable voltage output of the generator into the fixed frequency, fixed voltage output required for grid. 

Induction generator is stable at a:

Description : Induction generator is stable at a: 

Last Answer : Induction generator is stable at a: speed above synchronous speed

Consider the following statements: 1. A grid connected induction generator always supplies

Description : Consider the following statements:  1. A grid connected induction generator always supplies leading reactive power to the bus  2. An overexcited synchronous motor draws current at a lagging power factor  3. An underexcited synchronous ... (c) 1, 3 and 4 are correct (d) 1, 2, 3 and 4 are correct 

Last Answer : Consider the following statements:  1. A grid connected induction generator always supplies leading reactive power to the bus  2. An overexcited synchronous motor draws current at a lagging power factor  3. An underexcited ... correct (c) 1, 3 and 4 are correct (d) 1, 2, 3 and 4 are correct