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

1 Answer

Answer :

Ans: ZPF Lag

Related questions

Description : In the illustration, the signal from the device connected to terminals 18 and 19 is __________. EL-0046 A. prime mover speed feedback B. loss of control alarm when comparing with the input signal ... slip between the prime mover and the alternator D. to shut down the prime mover if overspeeding

Last Answer : Answer: A

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

Description : Which of the following is the demerit of a 'constant voltage transmission system' ? (a) Increase of short-circuit current of the system (b) Availability of steady voltage at all loads at ... of carrying increased power for a given conductor size in case of long-distance heavy power transmission

Last Answer : (a) Increase of short-circuit current of the system

Description : Which of the following is the demerit of a 'constant voltage transmission system' ? (a) Increase of short-circuit current of the system (b) Availability of steady voltage at all loads at ... of carrying increased power for a given conductor size in case of long-distance heavy power transmission

Last Answer : (a) Increase of short-circuit current of the system

Description : Possible phase relationships between voltage and current in an alternating current circuit include which of the following conditions? A. Current and voltage may be in phase. B. Current may lead the voltage. C. Current may lag the voltage. D. All of the above.

Last Answer : Answer: D

Description : An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging case. If it is required to deliver rated current at rated voltage and 0.8 power-factor leading, the required excitation will be (A) less. (B) more. (C) more or less. (D) the same.

Last Answer : Ans: B Over excitation gives leading power factor and under excitation gives lagging p.f .

Description : When the voltage and the current developed in an AC circuit reach their peak values at the same time, the power factor is considered to be _____________. A. lagging B. leading C. unity D. infinity

Last Answer : Answer: C

Description : To properly use a hook-on-type volt/ammeter to check current flow, you must FIRST _____________. A. de-energize the circuit to allow connection of the instrument in series B. hook the jaws ... test leads to the appropriate terminals D. short the test leads and calibrate the instrument to zero

Last Answer : Answer: B

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

Description : In an alternator at lagging power factor the generated voltage per phase as compared to that at unity power factor?

Last Answer : In an alternator, at lagging power factor the generated voltage per phase as compared to that at unity power factor must be more than terminal voltage.

Description : When Alternator excitation increases and machine is operating at lagging power factor then a) I increase b) I decreases c) No effect on current d) None

Last Answer : Ans: I increase

Description : A 'dead front' switchboard is one _____________. A. without switches on it B. with insulated switches and no exposed terminals C. without circuit breakers D. without safety hand rails nor rubber mats

Last Answer : Answer: B

Description : To remove an alternator operating in parallel with another unit from the main electrical bus, you must FIRST _________. A. adjust the power factor on both units B. set the desired voltage on ... C. open the circuit breaker on the outgoing alternator D. remove the load from the outgoing alternator

Last Answer : Answer: D

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

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

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

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

Description : In the illustration, the diode between terminals 16 and 17 is to _________. EL-0046 A. act as a short circuit for the sensing coil when CEMF is applied B. insure that the voltage across the coil does not exceed 9 volts C. improve response time D. act as a filter to prevent hunting

Last Answer : Answer: A

Description : Before touching a small capacitor connected to a de-energized circuit, or even one that is completely disconnected, you should ____________. A. gently tap the body with a screwdriver B. tag it ... insulated fuse puller D. short circuit the terminals to make sure that the capacitor is discharged

Last Answer : Answer: D

Description : A series circuit consists of a two ohm RESISTOR and a one ohm INDUCTOR. The relationship between current and voltage is: w) current will lag by 30 degrees. x) current will lag by 26 degrees. y) current will lead by 26 degrees. z) current will lead by 30 degrees.

Last Answer : ANSWER: X -- CURRENT WILL LAG BY 26 DEGREES.

Description : G(s) = (1+0.5s)/(1+s) find which type of net work it is a) Lead net work b) Lag net work c) Lag – Lead net work d) Lead – Lag net work

Last Answer : Ans: Lag net work

Description : A synchronous motor is operating on no-load at unity power factor. If the field current is increased, power factor will become (A) Leading & current will decrease (B) Lagging & current will increase. (C) Lagging & current will decrease. (D) Leading & current will increase.

Last Answer : Ans: A Initially synchronous motor is operating at no load and unity power factor. When field current increases, the excitation will increase. Therefore, p.f will be leading and current will be I CosΦ < I

Description : An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging. For delivering rated current at rated voltage and 0.8 poWer—factor leading, the required excitation will be:  (A) less  (B) more (C) more or less (D) the same

Last Answer : An alternator is delivering rated current at rated voltage and 0.8 power -factor lagging. For delivering rated current at rated voltage and 0.8 power -factor leading, the required excitation will be: more 

Description : A two-winding single phase transformer has a voltage regulation of 4.5% at full-load and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulation will be (A) 4.5%. (B) less than 4.5%. (C) more than 4.5%. (D) 4.5% or more than 4.5%.

Last Answer : (C) more than 4.5%.

Description : A 3-phase, 11 kv, 50 Hz, 200 kW load has a power factor of 0.8 lag. A delta connected 3-phase capacitor is used to improve the power factor to unity. The capacitance perphase of the capacitor in micro-farads is?

Last Answer : A 3-phase, 11 kv, 50 Hz, 200 kW load has a power factor of 0.8 lag. A delta connected 3-phase capacitor is used to improve the power factor to unity. The capacitance perphase of the capacitor in micro-farads is 1.316.

Description : A large AC generator, supplying power to an infinite bus, has a sudden short-circuit occurring at its terminals. Assuming the prime mover input and the voltage behind the transient reactance to remain constant immediately after the fault, acceleration of the generator rotor is

Last Answer : A large AC generator, supplying power to an infinite bus, has a sudden short-circuit occurring at its terminals. Assuming the prime mover input and the voltage behind the transient reactance ... , acceleration of the generator rotor is inversely proportional to the moment of inertia of the machine

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

Description : increases the steady state accuracy. (a) Integrator (b) Differentiator (c) Phase lead compensator (d) Phase lag compensator Ans:A 10.As a result of introduction of negative feedback which of the following will not decrease ? (a) Band width (b) Overall gain (c) Distortion (d) Instability

Last Answer : Ans: A

Description : A circuit breaker for a 300 KW alternator is rated at 470 amperes of full continuous load. The amount of overcurrent allowed is 125%. Which of the following conditions will trip the breaker? A. ... 10 minutes. C. Momentary starting load of 550 amperes. D. Sustained current flow of 590 amperes.

Last Answer : Answer: D

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 : (C) solid connections.

Description : When using a multimeter for resistance measurements, it should be calibrated by clipping the loose ends of the leads together and _____________. A. setting the instrument pointer at 'zero' ohms B. ... the plus and minus terminals D. using a special purpose resistance measuring instrument (a bridge)

Last Answer : Answer: A

Description : Which of the substances listed should be applied to battery terminals to help prevent corrosion? A. Zinc chromate B. Naval jelly C. Lead peroxide D. Petroleum jelly

Last Answer : Answer: D

Description : A breakable, mercury-filled thermometer should not be used in a lead-acid battery to measure electrolyte temperature, as an accidental breakage can cause ____________. A. severe sparking and explosions ... battery plates C. violent gassing at the positive plates D. corrosion on the battery terminals

Last Answer : Answer: A

Description : Routine maintenance of lead acid batteries should include _____________. A. keeping the terminals clean B. coating cable connections with petroleum jelly C. maintaining a trickle charge D. all of the above

Last Answer : Answer: D

Description : If the excitation of an alternator operating in parallel is decreased below normal, its _____________. A. power factor will change in the lagging direction B. power factor will change in the leading direction C. ampere load will be greatly increased D. kilowatt load will be greatly decreased

Last Answer : Answer: B

Description : What is the power factor of an alternator at no load?

Last Answer : Answer:At no load Synchronous Impedance of the alternator is responsible for creating angle difference. So it should be zero lagging like inductor.

Description : Explain armature reaction of an alternator and its effect on main flux at various power factor.

Last Answer : 1. zero lagging pf: armature flux lags main flux by 180 . Hence effect is demagnetizing i.e the main flux is reduced 2. lagging pf: it has 2 components demagnetizing and cross magnetizing ... 5. zero leading pf: Armature flux is in phase with main flux. Effect is completely magnetizing.

Description : The purpose of the reverse power relay, provided on a ship's service alternator panel, is to trip the circuit in the event of ______________. A. main circuit overload B. high power transfer C. generator overspeeding D. alternator motorization

Last Answer : Answer: D

Description : The purpose of a main switchboard circuit breaker's reverse-power trip is to _____________. A. prevent main circuit overload B. protect the circuit breaker blowout coil C. prevent alternator motorization D. prevent low voltage tripout

Last Answer : Answer: C

Description : Due to the operating characteristics of the system, time lag fuses (or dual-element fuses) are necessary for use in _____________. A. main lighting circuits B. motor starting circuit C. emergency lighting circuits D. general alarm circuits

Last Answer : Answer: B

Description : When is the Ferranti effect on long over head lines experienced? a) The lines are lightly loaded b) The lines are heavily loaded c) The lines are fully loaded d) The power factor is unity

Last Answer : Ans: A

Description : A transformer has negative voltage regulation when its load power factor is- (a) Zero (b) Unity (c) Leading (d) Lagging

Last Answer : Ans: C

Description : Power (P) in a 3 phase circuit with two watt meters at unity power factor is (W1 & W2 = watt meter readings)

Last Answer : Power (P) in a 3 phase circuit with two watt meters at unity power factor is P = W1 + W2 (W1 & W2 = watt meter readings)

Description : When troubleshooting a lead-acid storage battery, a weak or dead cell is best detected by _________________. A. measuring and comparing all cells' specific gravity B. taking an open circuit ... electrolyte levels of each cell D. taking each cell's temperature with a calibrated mercury thermometer

Last Answer : Answer: A

Description : In the illustration, the contacts between terminals 26 and 27 should be closed when _________. EL-0046 A. using one generator in isochronous mode only B. using two or more generators in ... through varying loads in parallel or single operation D. the circuit breaker is closed for that generator

Last Answer : Answer: C

Description : When working on electrical circuits containing large capacitors, in addition to deenergizing the circuit, which of the listed precautions should also be taken? A. Keep all radio equipment ... capacitor insulation resistance. C. Ground the capacitor terminals. D. Check capacitor circuit polarity.

Last Answer : Answer: C

Description : The ring circuit of the system shown in the illustration would become inoperative if a ground developed at ____________. EL-0093 A. either terminal 'T' or 'C' B. either terminal 'B' or 'R' C. both terminals 'B' and 'C' D. both terminals 'T' and 'R'

Last Answer : Answer: C

Description : If you obtain a low resistance reading with a megohmmeter connected between terminals 'A' and 'C' of the three-phase, wye-connected winding shown in the illustration, there is __________. EL-0074 A. no open circuit ... 'B' C. an open circuit between 'A' and 'C' D. an open circuit in both windings

Last Answer : Answer: A

Description : Which of the listed conditions will occur if dirt and grease are allowed to accumulate between the commutator segments of a motor? A. A partial short circuit. B. A dead short circuit. C. Misalignment of the motor shaft. D. Overspeeding of the motor.

Last Answer : Answer: A