During 3-phase short circuit on a unloaded alternator, the dc component may be zero in

During 3-phase short circuit on a unloaded alternator, the dc component may be zero in (1) One phase only (2) Any two phases (3) All three phases (4) None of the above 
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The severity of line to ground and three phase faults at the terminals of an unloaded

Description : The severity of line to ground and three phase faults at the terminals of an unloaded synchronous generator is to be same. If the terminal voltage is 1.0 pu, Z1=Z2=j0.1 p.u. and Z0= j0.05 p.u. for the alternator, then the required inductive ... a) 0.05 p.u. (b) 0.0166 p.u. (c) 0.1 p.u. (d) 0.15 p.u.

Last Answer : The severity of line to ground and three phase faults at the terminals of an unloaded synchronous generator is to be same. If the terminal voltage is 1.0 pu, Z1=Z2=j0.1 p.u. and Z0= j0.05 p.u. for the alternator, then the required inductive reactance for neutral grounding is 0.0166 p.u.

Why is it dangerous yo supply power to an unloaded series connected dc motor?

Description : Why is it dangerous yo supply power to an unloaded series connected dc motor?

Last Answer : Need answer

The output voltage of a three-phase alternator is regulated by the _____________. A. AC voltage to the armature B. AC voltage to the field C. DC voltage to the armature D. DC voltage to the field

Description : The output voltage of a three-phase alternator is regulated by the _____________. A. AC voltage to the armature B. AC voltage to the field C. DC voltage to the armature D. DC voltage to the field

Last Answer : Answer: D

If a unloaded shunt motor's field were weakened by rheostat resistance or by an open circuit, the motor would _________. A. overspeed due to reduced CEMF B. stop because of low flux C. continue to run at base speed D. slow down and overheat

Description : If a unloaded shunt motor's field were weakened by rheostat resistance or by an open circuit, the motor would _________. A. overspeed due to reduced CEMF B. stop because of low flux C. continue to run at base speed D. slow down and overheat

Last Answer : Answer: A

A d.c. voltage of 230 V is imposed on an unloaded 230 V, 50 Hz transformer, it will

Description : A d.c. voltage of 230 V is imposed on an unloaded 230 V, 50 Hz transformer, it will (A) give high secondary voltage (B) burn out (C) give secondary voltage as per k (D) None of these

Last Answer : A d.c. voltage of 230 V is imposed on an unloaded 230 V, 50 Hz transformer, it will burn out

At dead short circuit at terminals of Alternator then the current I is a) ZPF Lag b) ZPF lead c) Unity power factor d) 0.8 Power factor lag

Description : At dead short circuit at terminals of Alternator then the current I is a) ZPF Lag b) ZPF lead c) Unity power factor d) 0.8 Power factor lag

Last Answer : Ans: ZPF Lag

A field excitation of 20 A in a certain alternator results in an armature current of 400 A in short circuit and a

Description : A field excitation of 20 A in a certain alternator results in an armature current of 400 A in short circuit and a terminal voltage of 2000 V on open circuit. The magnitude of the internal voltage drop within the machine at a load current of 200 A is  (A) 1 V (B) 10 V (C) 100 V (D) 1000 V

Last Answer : 800

Which of the following problems will occur if the circuit breaker of the incoming alternator is closed and it is 180° out of phase with the loaded alternator when paralleling? A. The rotor of the loaded alternator will hunt. B. Severe cross currents will occur which could cause damage. C. The rotor of the incoming alternator will stop. D. Both alternators will parallel 180° out of phase.

Description : Which of the following problems will occur if the circuit breaker of the incoming alternator is closed and it is 180° out of phase with the loaded alternator when paralleling? A. The rotor of the ... The rotor of the incoming alternator will stop. D. Both alternators will parallel 180° out of phase.

Last Answer : Answer: B

In a half wave rectifier the rms value of AC component of the waves (a) Zero (b) Equal to DC value (c) More than DC value (d) Less than DC value

Description : In a half wave rectifier the rms value of AC component of the waves (a) Zero (b) Equal to DC value (c) More than DC value (d) Less than DC value

Last Answer : b) Equal to DC value

In a dc-ac 3-phase MOSFET bridge inverter circuit, the switches are marked in a sequence as 1, 2, 3 in the...

Description : In a dc-ac 3-phase MOSFET bridge inverter circuit, the switches are marked in a sequence as 1, 2, 3 in the top-half and 4, 5, 6 in the bottom half of the bridge. The triggering sequence of switches that gives balanced output voltage is (A) 1 ... 3, 4, 2, 6 (C) 1, 6, 2, 4, 3, 5 (D) 1, 4, 2, 5, 3, 6

Last Answer : In a dc-ac 3-phase MOSFET bridge inverter circuit, the switches are marked in a sequence as 1, 2, 3 in the top-half and 4, 5, 6 in the bottom half of the bridge. The triggering sequence of switches that gives balanced output voltage is 1, 6, 2, 4, 3, 5

In a 3 -phase alternator, if there is only magnetizing armature reaction, the load is :

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

Last Answer : In a 3 -phase alternator, if there is only magnetizing armature reaction, the load is : capacitive 

A alternator is delivering power to a balanced load at unit power factor. The phase angle between the line...

Description : A alternator is delivering power to a balanced load at unit power factor. The phase angle between the line voltage and the line current is? (A) 90° (B) 60° (C) 30° (D) 0° 

Last Answer : A alternator is delivering power to a balanced load at unit power factor. The phase angle between the line voltage and the line current is 30°

The current from the stator of an alternator is taken out to the external load circuit through:

Description : The current from the stator of an alternator is taken out to the external load circuit through: (A) slip rings (B) commutator segments (C) solid connections (D) carbon brushes

Last Answer : D  is correct

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

When 220V dc shunt alternator generating the voltage at rated value. If direction of rotation is reversed, then alternator will a) Build up its voltage with same polarity b) Build up its voltage with opposite polarity c) No build up of voltage d) None

Description : When 220V dc shunt alternator generating the voltage at rated value. If direction of rotation is reversed, then alternator will a) Build up its voltage with same polarity b) Build up its voltage with opposite polarity c) No build up of voltage d) None

Last Answer : Ans: No build up of voltage

Have you ever been unloaded on item wise?

Description : Have you ever been unloaded on item wise?

Last Answer : No, but I would welcome such a gift. I have no illusions that things I own will stay in perfect condition forever.

A boat carrying a number of large stones is floating in a water tank. If the stones are unloaded into the water, the level of water in the tank (a) Will remain unchanged (b) Will rise (c) Will fall (d) Will rise till half the number of stones are unloaded and then will begin to fall

Description : A boat carrying a number of large stones is floating in a water tank. If the stones are unloaded into the water, the level of water in the tank (a) Will remain unchanged (b) Will rise (c) Will fall (d) Will rise till half the number of stones are unloaded and then will begin to fall

Last Answer : Ans:(c)

Axial length of an unloaded helical compression spring is called (A) compressed length (B) solid length (C) free length (D) none of the above

Description : Axial length of an unloaded helical compression spring is called (A) compressed length (B) solid length (C) free length (D) none of the above

Last Answer : (C) free length

Resilience is defined as the property of material to absorb energy when deformed _________ and to release this energy when unloaded. a) Elastically b) Plastically c) Up to fracture point d) None of the listed

Description : Resilience is defined as the property of material to absorb energy when deformed _________ and to release this energy when unloaded. a) Elastically b) Plastically c) Up to fracture point d) None of the listed

Last Answer : a) Elastically

A spring of mean radius 40 mm contains 8 action coils of steel (N = 80000 N/mm2 ), 4 mm in diameter. The clearance between the coils being 1 mm when unloaded, the minimum compressive load to remove the clearance, is (A) 25 N (B) 30 N (C) 35 N (D) 40 N

Description : A spring of mean radius 40 mm contains 8 action coils of steel (N = 80000 N/mm2 ), 4 mm in  diameter. The clearance between the coils being 1 mm when unloaded, the minimum compressive  load to remove the clearance, is  (A) 25 N  (B) 30 N  (C) 35 N  (D) 40 N 

Last Answer : (C) 35 N 

Why is an air compressor started unloaded?

Description : Why is an air compressor started unloaded?

Last Answer : The air pressure inside the compressor cylinder offers resistance to the movement of the piston. Hence started unloaded. Ask 4/E or 2/E in ship.

If the field circuits of an unloaded salient pole synchronous motor gets suddenly open circuited, then (A) The motor stops. (B) It continues to run at the same speed. (C) Its runs at the slower speed. (D) It runs at a very high speed.

Description : If the field circuits of an unloaded salient pole synchronous motor gets suddenly open circuited, then (A) The motor stops. (B) It continues to run at the same speed. (C) Its runs at the slower speed. (D) It runs at a very high speed.

Last Answer : Ans: B The motor continues to run at the same speed because synchronous motor speed does not depend upon load, Nα f.

If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will?

Last Answer : If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will stop.

what will happen when excitation of an unloaded salient pole synchronous motor suddenly gets disconnected?

Description : what will happen when excitation of an unloaded salient pole synchronous motor suddenly gets disconnected?

Last Answer : When excitation of an unloaded salient pole synchronous motor suddenly gets disconnected the motor will stop.

When liquid and vapour phase of multi-component system are in equilibrium (at a given temperature and pressure), then chemical potential of each component is (A) Same in both the phases (B) Zero in both the phases (C) More in vapour phase (D) More in liquid phase

Description : When liquid and vapour phase of multi-component system are in equilibrium (at a given temperature and pressure), then chemical potential of each component is (A) Same in both the phases (B) Zero in both the phases (C) More in vapour phase (D) More in liquid phase

Last Answer : (A) Same in both the phases

For a single component two phase mixture, the number of independent variable properties are (A) Two (B) One (C) Zero (D) Three

Description : For a single component two phase mixture, the number of independent variable properties are (A) Two (B) One (C) Zero (D) Three

Last Answer : (B) One

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

In case of a 3-phase short-circuit fault in a system, the power fed into the system is

Description : In case of a 3-phase short-circuit fault in a system, the power fed into the system is   (a) Mostly reactive (b) Reactive only (c) Mostly active (d) Active and Reactive both equal 

Last Answer : In case of a 3-phase short-circuit fault in a system, the power fed into the system is Mostly reactive 

Why is core loss zero during short circuit test ?

Description : Why is core loss zero during short circuit test ?

Last Answer : The voltage applied by the varicus on the high side is very low , so the mutual flux in the core is also very low. So core loss is zero.

Circuit breakers usually operate under (a) transient state of short-circuit current (b) sub-transient state of short-circuit current (c) steady state of short-circuit current (d) after D.C. component has ceased

Description : Circuit breakers usually operate under (a) transient state of short-circuit current (b) sub-transient state of short-circuit current (c) steady state of short-circuit current (d) after D.C. component has ceased

Last Answer : (a) transient state of short-circuit current

A short circuit in the armature of a DC motor will cause the motor to _____________. A. run fast B. hum when energized C. spark at the brushes D. fail to start

Description : A short circuit in the armature of a DC motor will cause the motor to _____________. A. run fast B. hum when energized C. spark at the brushes D. fail to start

Last Answer : Answer: C

Which of the following is not true: A) An oscillator is a circuit that converts DC to AC B) An oscillator is an amplifier that supplies its own input signal C) All oscillators generate sine waves D) In phase feedback is called positive Feedback

Description : Which of the following is not true: A) An oscillator is a circuit that converts DC to AC B) An oscillator is an amplifier that supplies its own input signal C) All oscillators generate sine waves D) In phase feedback is called positive Feedback

Last Answer : C) All oscillators generate sine waves

An open occurring within the field rheostat of an AC generator can be detected by short circuiting its terminals and observing a ____________. A. negative deflection of the wattmeter pointer B. positive deflection of the wattmeter pointer C. buildup of alternator voltage D. low, but constant alternator voltage

Description : An open occurring within the field rheostat of an AC generator can be detected by short circuiting its terminals and observing a ____________. A. negative deflection of the wattmeter pointer B. ... of the wattmeter pointer C. buildup of alternator voltage D. low, but constant alternator voltage

Last Answer : Answer: C

Advantages of Short Pitch Coils for an Alternator

Description : Advantages of Short Pitch Coils for an Alternator

Last Answer : Advantages of Short Pitch Coils for an Alternator: (1) It gives better sinusoidal waveform by reducing the harmonic components. (2) It saves copper as length required for the connections is ... are illuminated, hysteresis & eddy current losses will be reduced and this increases the efficiency.

In an alternator if the winding is short pitched by 60 electrical degrees, its pitch factor will be:

Description :  In an alternator if the winding is short pitched by 60 electrical degrees, its pitch factor will be: A) 1.0 B) 0.866 C) 0.75 D) 0.50

Last Answer :  In an alternator if the winding is short pitched by 60 electrical degrees, its pitch factor will be: A) 1.0 B) 0.866 C) 0.75 D) 0.50

A three-phase alternator is operating at 450 volts, 250 amps at 0.6 power factor. If the power factor increases to 0.8, the kw load potential will increase by _____________. A. 38.525 kw B. 116.91 kw C. 155.88 kw D. 194.85 kw

Description : A three-phase alternator is operating at 450 volts, 250 amps at 0.6 power factor. If the power factor increases to 0.8, the kw load potential will increase by _____________. A. 38.525 kw B. 116.91 kw C. 155.88 kw D. 194.85 kw

Last Answer : Answer: A

A three-phase alternator operates at 450 volts with a power factor of 0.8. If the ammeter indicates 250 amperes, what should be the KW meter reading? A. 90.00 KW B. 127.27 KW C. 155.70 KW D. 194.85 KW

Description : A three-phase alternator operates at 450 volts with a power factor of 0.8. If the ammeter indicates 250 amperes, what should be the KW meter reading? A. 90.00 KW B. 127.27 KW C. 155.70 KW D. 194.85 KW

Last Answer : Answer: C

A three-phase alternator is developing 300 amps, with a 0.8 power factor, at 450 volts. The true indicated power on the kilowatt meter, located on the main switchboard, will be ____________. A. 133 kw B. 155 kw C. 187 kw D. 212 kw

Description : A three-phase alternator is developing 300 amps, with a 0.8 power factor, at 450 volts. The true indicated power on the kilowatt meter, located on the main switchboard, will be ____________. A. 133 kw B. 155 kw C. 187 kw D. 212 kw

Last Answer : Answer: C

A three-phase alternator is operating at 450 volts with the switchboard ammeter indicating 300 amps. The kw meter currently indicates 163.6 KW, with a power factor of 0.7. If the power factor increases to 0.8, the KW meter would then read ____________. A. 181.4 KW B. 186.8 KW C. 194.2 KW D. 201.4 KW

Description : A three-phase alternator is operating at 450 volts with the switchboard ammeter indicating 300 amps. The kw meter currently indicates 163.6 KW, with a power factor of 0.7. If the power factor increases to 0.8, the KW meter would then read ____________. A. 181.4 KW B. 186.8 KW C. 194.2 KW D. 201.4 KW

Last Answer : Answer: B

For the illustrated wiring of a three phase alternator, which statement is true about the current? EL-0074 A. phase current is 1.73 times the line current B. line current is 1.73 times the phase current C. there is no relationship between phase current and line current D. line current is equal to phase current

Description : For the illustrated wiring of a three phase alternator, which statement is true about the current? EL-0074 A. phase current is 1.73 times the line current B. line current is 1.73 times the ... . there is no relationship between phase current and line current D. line current is equal to phase current

Last Answer : Answer: D

In the illustrated three phase alternator, line voltage is _________. EL-0074 A. 1.73 times the phase voltage B. equal to the phase voltage C. phase voltage divided by 1.73 D. unable to answer this question without knowing the line current

Description : In the illustrated three phase alternator, line voltage is _________. EL-0074 A. 1.73 times the phase voltage B. equal to the phase voltage C. phase voltage divided by 1.73 D. unable to answer this question without knowing the line current

Last Answer : Answer: A

When paralleling two alternators, the synchronizing lamps remain lit as the synchroscope pointer approaches the 0°. This indicates the _____________. A. incoming alternator is running too fast B. alternator voltages are 180 degrees apart C. synchroscope is defective or broken D. alternator power factors are in phase

Description : When paralleling two alternators, the synchronizing lamps remain lit as the synchroscope pointer approaches the 0°. This indicates the _____________. A. incoming alternator is running too fast B. alternator ... apart C. synchroscope is defective or broken D. alternator power factors are in phase

Last Answer : Answer: C

When paralleling two alternators the synchronizing lamps grow dim and are totally darkened as the synchroscope pointer approaches the 0° position. This indicates the ____________. A. alternator voltages are 180° apart B. incoming alternator is running too fast C. incoming alternator is in phase with the bus voltage D. synchroscope pointer is defective or broken

Description : When paralleling two alternators the synchronizing lamps grow dim and are totally darkened as the synchroscope pointer approaches the 0° position. This indicates the ____________. A. alternator voltages ... alternator is in phase with the bus voltage D. synchroscope pointer is defective or broken

Last Answer : Answer: C

When paralleling two alternators using three synchronizing lamps, the flickering of all three lamps becomes progressively slower and slower. This means the ______________. A. frequency of the incoming generator is approaching that of the bus B. frequency of the incoming alternator is less than that of the bus C. phase rotation of the incoming alternators is opposite to that of the bus D. terminal voltage of the incoming alternator is approaching that of the bus

Description : When paralleling two alternators using three synchronizing lamps, the flickering of all three lamps becomes progressively slower and slower. This means the ______________. A. frequency of the incoming ... the bus D. terminal voltage of the incoming alternator is approaching that of the bus

Last Answer : Answer: A

A three-phase alternator is operating at 450 volts with the switchboard ammeter indicating 300 amps. The kw meter currently indicates 163.6 KW, with a power factor of 0.7. If the power factor increases to 0.8, the KW meter reading would increase by ___ A. 17.8 KW B. 23.2 KW C. 30.6 KW D. 37.8 KW

Description : A three-phase alternator is operating at 450 volts with the switchboard ammeter indicating 300 amps. The kw meter currently indicates 163.6 KW, with a power factor of 0.7. If the power factor increases to 0.8, the KW meter reading would increase by ___ A. 17.8 KW B. 23.2 KW C. 30.6 KW D. 37.8 KW

Last Answer : Answer: B

Name the various methods for predetermining the voltage regulation of 3-phase Alternator.

Description : Name the various methods for predetermining the voltage regulation of 3-phase Alternator.

Last Answer : The following are the three methods which are used to predetermine the voltage regulation of smooth cylindrical type Alternators · Synchronous impedance / EMF method · Ampere-turn / MMF method · Potier / ZPF method

What are the two methods of connecting the outputs from a three-phase alternator to the load?

Description : What are the two methods of connecting the outputs from a three-phase alternator to the load?

Last Answer : Wye and Delta.