How alternators are rated?

How alternators are rated?
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Alternators are rated in kVA.
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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

Why alternators are rated in KVA?

Description : Why alternators are rated in KVA?

Last Answer : The KVA rating of ac machine depends on the power factor of the load. The power factor in turn depends on the operating conditions. The operating conditions differ from place to place. Therefore the KVA rating is specified for all ac machines.

Why are Alternators rated in kVA and not in kW?

Description : Why are Alternators rated in kVA and not in kW?

Last Answer : The continuous power rating of any machine is generally defined as the power the machine or apparatus can deliver for a continuous period so that the losses incurred in the machine gives rise to a ... generator , the Alternators have only their apparent power in VA/kVA/MVA as their power rating.

Two alternators rated are 200 KW at 4% regulation, 400 KW 5% regulation operating in parallel at 50HZ , when supply 600 KW the new frequency is a) 50 b) 49 c) 51.3 d) 47.7

Description : Two alternators rated are 200 KW at 4% regulation, 400 KW 5% regulation operating in parallel at 50HZ , when supply 600 KW the new frequency is a) 50 b) 49 c) 51.3 d) 47.7

Last Answer : Ans: 47.7

How are alternators usually rated?

Description : How are alternators usually rated?

Last Answer : Kilovolt-amperes (volt amperes).

The graph shown in the illustration represents the speed droop curves of two equal capacity alternators about to be paralleled. When paralleled, the greater portion of the total load above 60% for each unit will be picked up _____________. EL-0025 A. by unit 'A' B. by unit 'B' C. equally by each unit D. none of the above

Description : The graph shown in the illustration represents the speed droop curves of two equal capacity alternators about to be paralleled. When paralleled, the greater portion of the total load above 60% for each unit will be picked up ... unit 'A' B. by unit 'B' C. equally by each unit D. none of the above

Last Answer : Answer: A

The load sharing characteristics of two diesel alternators operating in parallel are directly related to the setting of their governors' ____________. A. load limit B. idle speed C. speed limit D. speed droop

Description : The load sharing characteristics of two diesel alternators operating in parallel are directly related to the setting of their governors' ____________. A. load limit B. idle speed C. speed limit D. speed droop

Last Answer : Answer: D

Which of the following statements is true concerning the operation of two alternators in parallel? A. The cycles per second of each alternator are the same. B. Both alternator governors must be set with the same amount of speed droop. C. The number of field poles must be the same on each alternator. D. The load must always be divided equally between alternators.

Description : Which of the following statements is true concerning the operation of two alternators in parallel? A. The cycles per second of each alternator are the same. B. Both alternator governors must be set ... be the same on each alternator. D. The load must always be divided equally between alternators.

Last Answer : Answer: A

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

Equalization of the power factors of two alternators operating in parallel is accomplished _____________. A. manually, by adjusting the governor controls B. automatically, by automatic voltage regulators C. manually, adjusting the output of current transformers D. automatically, by the designed action of the governors

Description : Equalization of the power factors of two alternators operating in parallel is accomplished _____________. A. manually, by adjusting the governor controls B. automatically, by automatic voltage regulators ... the output of current transformers D. automatically, by the designed action of the governors

Last Answer : Answer: B

After closing the circuit breaker to place two similar alternators in parallel, the NEXT step is to balance the _____________. A. power factor B. voltage load C. kilowatt load D. ampere load

Description : After closing the circuit breaker to place two similar alternators in parallel, the NEXT step is to balance the _____________. A. power factor B. voltage load C. kilowatt load D. ampere load

Last Answer : Answer: C

Why is it a good practice to have the frequency of the incoming alternator adjusted slightly higher than that of the loaded alternator when paralleling two alternators? A. This allows the oncoming machine to accept load immediately. B. This prevents the machine from floating on the line. C. The reverse power relay is prevented from activating. D. All of the above.

Description : Why is it a good practice to have the frequency of the incoming alternator adjusted slightly higher than that of the loaded alternator when paralleling two alternators? A. This allows the oncoming machine to ... line. C. The reverse power relay is prevented from activating. D. All of the above.

Last Answer : Answer: D

The KW load is evenly distributed between two alternators just placed in parallel by adjusting _____________. A. a balance coil B. the governor settings C. the field excitation D. a rheostat

Description : The KW load is evenly distributed between two alternators just placed in parallel by adjusting _____________. A. a balance coil B. the governor settings C. the field excitation D. a rheostat

Last Answer : Answer: B

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

If the pointer of the synchroscope is rotating in the slow direction when you are preparing to parallel two alternators, the _____________. A. incoming machine is turning faster than the load alternator B. loaded alternator is turning faster than the incoming machine C. load on the loaded alternator is ready to split D. incoming machine is beginning to pick up some of the load

Description : If the pointer of the synchroscope is rotating in the slow direction when you are preparing to parallel two alternators, the _____________. A. incoming machine is turning faster than the load alternator B ... alternator is ready to split D. incoming machine is beginning to pick up some of the load

Last Answer : Answer: B

You are paralleling two alternators. The synchronizing lamps grow dim and are totally darkened as the synchroscope pointer approaches the 0° position. This indicates that the ____________. A. alternator voltages are 180° apart B. circuit breaker can be closed C. incoming alternator is running too slowly D. synchroscope is defective or broken

Description : You are paralleling two alternators. The synchronizing lamps grow dim and are totally darkened as the synchroscope pointer approaches the 0° position. This indicates that the ____________. A. alternator ... be closed C. incoming alternator is running too slowly D. synchroscope is defective or broken

Last Answer : Answer: B

If the excitation is increased to one of two alternators operating in parallel, the _____________. A. power factor will change in the lagging direction B. power factor will change in the leading direction C. kilowatt load will be greatly increased D. ampere load will be greatly decreased

Description : If the excitation is increased to one of two alternators operating in parallel, the _____________. A. power factor will change in the lagging direction B. power factor will change in the leading direction C. kilowatt load will be greatly increased D. ampere load will be greatly decreased

Last Answer : Answer: A

To equalize the power factor of two alternators operating in parallel, the ____________. A. field excitation of both units is adjusted B. governors of both units are adjusted C. phase sequence is altered D. kilowatt load is evenly divided

Description : To equalize the power factor of two alternators operating in parallel, the ____________. A. field excitation of both units is adjusted B. governors of both units are adjusted C. phase sequence is altered D. kilowatt load is evenly divided

Last Answer : Answer: A

Which of the following devices are protected from being motorized by a reversepower relay? A. Alternators B. Wave guides C. Exciters D. Amplidynes

Description : Which of the following devices are protected from being motorized by a reversepower relay? A. Alternators B. Wave guides C. Exciters D. Amplidynes

Last Answer : Answer: A

The division of kilowatt load between two paralleled alternators is determined by the _____________. A. amount of field excitation of the leading machine B. load-speed characteristics of the governors C. amount of field excitation to the lagging machine D. type of alternator

Description : The division of kilowatt load between two paralleled alternators is determined by the _____________. A. amount of field excitation of the leading machine B. load-speed characteristics of the governors C. amount of field excitation to the lagging machine D. type of alternator

Last Answer : Answer: B

The division of kilowatt load between two paralleled alternators is determined by the _____________. A. amount of field excitation to the leading machine B. load-speed characteristics of the governors C. amount of field excitation to the lagging machine D. number of field poles per alternator

Description : The division of kilowatt load between two paralleled alternators is determined by the _____________. A. amount of field excitation to the leading machine B. load-speed characteristics of the governors C. amount of field excitation to the lagging machine D. number of field poles per alternator

Last Answer : Answer: B

Handheld phase sequence indicators are useful when ________. A. preparing to parallel alternators B. connecting lighting branch circuits C. troubleshooting DC motors D. connecting shore power lines to the ship

Description : Handheld phase sequence indicators are useful when ________. A. preparing to parallel alternators B. connecting lighting branch circuits C. troubleshooting DC motors D. connecting shore power lines to the ship

Last Answer : Answer: D

Which of the following statements is true concerning all three-phase alternators? A. Each has three separate but identical armature windings acted on by one system of rotating magnets. B. Each has one armature winding acted on by three identical but separate systems of rotating magnets. C. All three-phase alternators are designed to operate with a 0.8 leading power factor. D. The three phases always provide power to the load through three sets of slip rings and brushes.

Description : Which of the following statements is true concerning all three-phase alternators? A. Each has three separate but identical armature windings acted on by one system of rotating magnets. B. Each has one ... The three phases always provide power to the load through three sets of slip rings and brushes.

Last Answer : Answer: A

What Are The Various Types Of Rotors Used In The Alternators?

Description : What Are The Various Types Of Rotors Used In The Alternators?

Last Answer : Salient pole rotor Non- salient pole rotor and Cylindrical rotor

Will The Alternators Have Rotating Armature System Or Stationary Armature System?

Description : Will The Alternators Have Rotating Armature System Or Stationary Armature System?

Last Answer : Generally in alternators, the armature is stationary and the field rotates. Small low-voltage alternators often have a rotating armature and a stationary field winding. But in large alternators rotating armature field type is used.

What Is Meant By Turbo Alternators?

Description : What Is Meant By Turbo Alternators?

Last Answer : Turbo alternators are high speed alternators. Because of high speed of rotation, the rotor diameter is reduced and the axial length is increased. Two or four poles are generally used and steam turbines are used as prime movers.

What Is Basic Principle Of Operation Of Alternators/dc Generators?

Description : What Is Basic Principle Of Operation Of Alternators/dc Generators?

Last Answer : They are working on the fundamental principle based on Faraday’s Laws of Electromagnetic Induction. This law states that, When a current carrying conductor moves in magnetic field, it induces an EMF.

How synchronoscope is used for synchronizing Alternators?

Description : How synchronoscope is used for synchronizing Alternators?

Last Answer : Synchronoscope can be used for permanently connected Alternators where the correctness of phase sequence is already checked by other means. The rotation of pointer is proportional to the difference in ... alternator is running slow. If the difference in frequency is large the pointer will oscillate

State the condition to be satisfied before connecting two alternators in parallel

Description : State the condition to be satisfied before connecting two alternators in parallel

Last Answer : The following are the three conditions to be satisfied by synchronizing the additional Alternator with the existing one or the common bus-bars. · The terminal voltage magnitude of the incoming ... incoming Alternator voltage must be the same as the bus-bar voltage. . Zero phase difference

What is need of parallel operation of alternators?

Description : What is need of parallel operation of alternators?

Last Answer : 1. Optimum utilization of alternators as most of the power stations are interconnected by grid. 2. Reduced operating cost: number of alternators operating at a time can be changed depending on ... demands. 3. Easy maintenance: Alternator may be shut down for maintenance 4. Continuity and reliability

What are the causes of changes in voltage in Alternators when loaded?

Description : What are the causes of changes in voltage in Alternators when loaded?

Last Answer : When alternator is loaded the armature carries load current. Due to this load current the voltage drops occur in alternator. Hence terminal voltage decreases due to following voltage drops: 1. Voltage ... the leakage reactance of the winding, Xl 3· Voltage drop due to the armature reactance, Xa

What is meant by armature reaction in Alternators?

Description : What is meant by armature reaction in Alternators?

Last Answer : The effect of armature flux on main flux

Why do cylindrical Alternators operate with steam turbines?

Description : Why do cylindrical Alternators operate with steam turbines?

Last Answer : A: Steam turbines are found to operate at fairly good efficiency only at high speeds. The high speed operation of rotors tends to increase mechanical losses and so the rotors should have a ... axial length are used for Synchronous generators driven by steam turbines with either 2 or 4 poles.

How are alternators classified?

Description : How are alternators classified?

Last Answer : According to shape of field system · Salient pole type · Smooth cylindrical type

What are the causes of over speed and how alternators are protected from it?

Description : What are the causes of over speed and how alternators are protected from it?

Last Answer : Sudden loss of all or major part of the load causes over-speeding in alternators. Modern alternators are provided with mechanical centrifugal devices mounted on their driving shafts to trip the main valve of the prime mover when a dangerous over-speed occurs.

Which of the following precautions should be taken when a blown fuse, rated at 10 amperes, is replaced? A. Short out the fuse before removing it from the circuit. B. Use needle-nose pliers to remove fuse from the circuit. C. Replace blown fuse with one of equal voltage and ampere capacity. D. Fuses of 10 ampere rating and less are virtually harmless when energized and may be handled freely.

Description : Which of the following precautions should be taken when a blown fuse, rated at 10 amperes, is replaced? A. Short out the fuse before removing it from the circuit. B. Use needle-nose pliers to ... D. Fuses of 10 ampere rating and less are virtually harmless when energized and may be handled freely.

Last Answer : Answer: C

An open shunt field in a direct current machine may be located by connecting the field circuit to an external power source, equal to the rated field voltage or less, and tested with a voltmeter from _____________. A. one line terminal to each coil lead in succession B. one field coil to each adjacent field coil in turn C. any suitable ground to any available line lead D. any field pole to each field coil lead

Description : An open shunt field in a direct current machine may be located by connecting the field circuit to an external power source, equal to the rated field voltage or less, and tested with a voltmeter from ... C. any suitable ground to any available line lead D. any field pole to each field coil lead

Last Answer : Answer: A

A vessel is equipped with two ship's service generators. Generator #1 is rated at 900 kw and generator #2 is rated at 600 kw. During parallel operation, with a hotel load of 1,000 kw, what should be the kw load on generator #2? A. 100 kw B. 400 kw C. 500 kw D. 600 kw

Description : A vessel is equipped with two ship's service generators. Generator #1 is rated at 900 kw and generator #2 is rated at 600 kw. During parallel operation, with a hotel load of 1,000 kw, what should be the kw load on generator #2? A. 100 kw B. 400 kw C. 500 kw D. 600 kw

Last Answer : Answer: B

A turbogenerator has a rated output of 1200 KW at 60 Hertz, with a no load frequency of 61.5 Hertz. What is its speed droop? A. 1.03% B. 1.50% C. 2.44% D. 2.50%

Description : A turbogenerator has a rated output of 1200 KW at 60 Hertz, with a no load frequency of 61.5 Hertz. What is its speed droop? A. 1.03% B. 1.50% C. 2.44% D. 2.50%

Last Answer : Answer: D

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. Sustained current flow of 470 amperes. B. Sustained current flow of 500 amperes for 10 minutes. C. Momentary starting load of 550 amperes. D. Sustained current flow of 590 amperes.

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

Electric motors intended for use outside the engine room and boiler room are frequently rated to run at a designed ambient temperature of 40°C. What is the equivalent temperature in degrees Fahrenheit? A. 54.2°F B. 72.0°F C. 104.0°F D. 129.6°F

Description : Electric motors intended for use outside the engine room and boiler room are frequently rated to run at a designed ambient temperature of 40°C. What is the equivalent temperature in degrees Fahrenheit? A. 54.2°F B. 72.0°F C. 104.0°F D. 129.6°F

Last Answer : Answer: C

A single-phase induction motor starts, comes up to about 75% rated speed, slows down to a lower speed, and accelerates again. The problem is most likely in the ____________. A. starting winding B. running winding C. starting capacitor D. running centrifugal switch

Description : A single-phase induction motor starts, comes up to about 75% rated speed, slows down to a lower speed, and accelerates again. The problem is most likely in the ____________. A. starting winding B. running winding C. starting capacitor D. running centrifugal switch

Last Answer : Answer: B

A fuse will 'blow' if _____________. A. an electric motor is stopped suddenly by opening a switch B. the flow of current to the protection device is reversed C. the electrical current exceeds the rated value of the fuse D. unequal resistors are connected in parallel

Description : A fuse will 'blow' if _____________. A. an electric motor is stopped suddenly by opening a switch B. the flow of current to the protection device is reversed C. the electrical current exceeds the rated value of the fuse D. unequal resistors are connected in parallel

Last Answer : Answer: C

Fuses are usually rated in _____________. A. watts B. amps only C. volts only D. amps and volts

Description : Fuses are usually rated in _____________. A. watts B. amps only C. volts only D. amps and volts

Last Answer : Answer: D

A split-phase induction squirrel-cage motor will not come up to speed, even though the rated voltage, rated frequency, and rated load are applied. The suspected trouble could be due to _____________. A. a faulty centrifugal switch B. broken rotor bars C. worn bearings D. all of the above

Description : A split-phase induction squirrel-cage motor will not come up to speed, even though the rated voltage, rated frequency, and rated load are applied. The suspected trouble could be due to _____________. A. a faulty centrifugal switch B. broken rotor bars C. worn bearings D. all of the above

Last Answer : Answer: D

If the centrifugal switch or relay used for cutting out the starting winding of a split-phase induction motor fails to open once the motor is in operation, the _____________. A. motor will overspeed B. starting winding will burn out C. motor will immediately stall under load D. motor torque will be above normal at rated speed

Description : If the centrifugal switch or relay used for cutting out the starting winding of a split-phase induction motor fails to open once the motor is in operation, the _____________. A. motor will overspeed B ... C. motor will immediately stall under load D. motor torque will be above normal at rated speed

Last Answer : Answer: B

In the illustration, the purpose of part B is to _________. EL-0033 A. increase resistance in series with the contacts as they close to prevent arcing B. create a magnetic field in the steel plates that interacts with the arc to cool and extinguish the arc C. cause the contacts to open in the event of an overload D. provide ventilation to the contact when the breaker is close to rated capacity

Description : In the illustration, the purpose of part B is to _________. EL-0033 A. increase resistance in series with the contacts as they close to prevent arcing B. create a magnetic field in the steel ... event of an overload D. provide ventilation to the contact when the breaker is close to rated capacity

Last Answer : Answer: B