单选题The power factor of an AC generator operating singularly is determined by the ()Aconnected loadBprime mover speedCfield excitationDgenerators rated voltage

单选题
The power factor of an AC generator operating singularly is determined by the ()
A

connected load

B

prime mover speed

C

field excitation

D

generators rated voltage


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相关考题:

When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is _____.A.laggingB.leadingC.maximumD.minimum

The frequency of an AC generator is controlled by theA.rheostatB.governorC.exciterD.capacitor

The frequency of an AC generator is controlled by the ___.A.rheostatB.governorC.exciterD.capacitor

The power factor of an AC generator operating singularly is determined by the_______ .A.connected loadB.prime mover speedC.field excitationD.generator's rated voltage

材料:The field current supply in older machines comes from a lower voltage direct current generator or exciter on the same shaft as the alternator. Modern machines however are either statically excited or of the high-speed brush-less type. The exciter is required to operate to counter the effects of power factor for a given load. The power factor is a measure of the phase difference between voltage and current and is expressed as the cosine of the phase angle. With a purely resistance load the voltage and the current are in phase, giving a power factor of one. The power consumed is therefore the product of voltage and current. Inductive or capacitive loads, combined with resistance loads, produce lagging or leading power factors which have a value less than one.The power consumed is therefore the product of current, voltage and power factor. The alternating current generator supplying a load has a voltage drop resulting from the load. When the load has a lagging power factor this voltage drop is considerable. Therefore the exciter, in maintaining the alternator voltage, must vary with load current and also the power factor. The speed change of the prime mover must also be taken into account.问题: The word “machines” in the passage refers to _____.A.the direct current generatorB.the alternating current generatorC.the exciterD.the prime moverWhich of the following statements is true according to the passage ?A.With a purely resistance load, the power factor is zeroB.Inductive loads combined with resistance loads produces leading power factorsC.Capacitive loads combined with resistance loads produces lagging power factorsD.With a purely resistance load, the phase angle is zeroWhen the load has a lagging power factor this voltage drop is considerable. This sentence means that _____.A.with a purely resistance load, the voltage drops too muchB.there is a considerable voltage drop in the capacitive load combined with resistance loadC.when the load is the capacitive load combined with resistance load, the voltage drops to zeroD.when the load is the inductive load combined with resistance load, the voltage drop is fairly largeThe exciter must vary with: ① load current ② the power factor, ③ speed change of the prime mover.A.①B.②C.①②D.①②③请帮忙给出每个问题的正确答案和分析,谢谢!

英译汉:power factor

A laptop operates on battery power when connected with an AC adapter. Once the battery discharges, the computer turns off and will not turn back on. Which of the following are the MOST likely causes of the laptop issue? ()(Select TWO).A、The LCD monitor’s power inverter does not function properly.B、The operating system’s power settings prevent the battery from charging.C、The battery is not compatible with the laptop.D、The internal power connection on the motherboard is faulty.E、The power adapter is not working.

名词解释题英译汉:power factor

单选题The purpose of DC generator brushes is to ().Aneutralize armature reactionBconduct electric current to an outside circuitCconvert DC current to AC currentDprovide excitation to a DC generator

单选题A DC generator is used to supply direct current in order to maintain an AC generator field and is known as a/an ()ArotorBstatorCexciterDarmature

单选题Excessive vibration in an operating diesel generator may be caused by ()Aelectrical overloadBsurging at governed RPMCloose engine mounting boltsDcoolant leaking into the cylinder

单选题The division of the kilowatt load between two AC generators operating in parallel is controlled by the settings and characteristics of the ().Avoltage regulatorsBfield rheostatsCreverse power relaysDprime mover governors

单选题The load between two steam-driven alternators operating in parallel may be adjusted by varying ()Athe speed of the alternatorsBthe field strength of the machinesCthe power factor of the alternatorsDsteam supply to the prime movers

单选题The power factor of an AC generator operating singularly is determined by the ()Aconnected loadBprime mover speedCfield excitationDgenerators rated voltage

单选题The power factor at which a paralleled AC generator operates is usually adjusted by the ().Aconnected loadBprime mover speedCfield excitationDgenerators rated voltage

单选题When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is ()AlaggingBleadingCmaximumDminimum

单选题When securing an AC generator, you should FIRST ().Aopen the generator circuit breakerBswitch the voltage regulator to “manual”Cdecrease the field excitation to minimumDreduce the load on the unit

单选题The frequency of an AC generator is controlled by the ()ArheostatBgovernorCexciterDcapacitor

单选题To increase the frequency of an operating AC generator, you should ()Aincrease the field excitationBdecrease the field excitationCincrease the number of magnetic polesDincrease the speed of the prime mover

单选题Most often () is attached to the engine-propeller shaft for efficient electric power generation.Aa variable-speed AC generatorBa fixed-speed AC generatorCan air blowerDa DC generator

单选题Emergency generator is installed on board mainly to ()Aconnect to the busbar when the load increasingBsupply power specially to charging panelCbe put into operation during the ship arriving at or leaving portDensure the power supply to critical equipment after the main switchboard out of power

单选题Why is it desirable to operate paralleled AC generators at the same power factor?()ACirculating currents are kept to a minimumBField excitation losses are kept to a minimumCGenerator rotors will have a lesser tendency to huntDBecause a power factor increase will decrease kilowatt output

单选题The alternating current generator supplying a load has a voltage drop resulted from the loadWhen the load has a lagging power factor this voltage drop ().Ais smallBmay be neglectedCis usefulDis considerable

多选题A laptop operates on battery power when connected with an AC adapter. Once the battery discharges, the computer turns off and will not turn back on. Which of the following are the MOST likely causes of the laptop issue? ()(Select TWO).AThe LCD monitor’s power inverter does not function properly.BThe operating system’s power settings prevent the battery from charging.CThe battery is not compatible with the laptop.DThe internal power connection on the motherboard is faulty.EThe power adapter is not working.

单选题A diesel generator has just been paralleled with an AC turbo-generator, but the load can not be properly divided.This could be caused by()Aan incorrect diesel generator governor speed droop adjustmentBa faulty reverse power relay within the main circuit breaker assemblyCunsynchronized isochronous load distribution adjustmentsDa different speed setting on each unit

单选题To () , the power is supplied by main switchboard directly not though sub-board.Asave network costBimprove the reliability of supplying power to important loadCprevent sequence reverseDincrease the power factor of important load

单选题To equalize the power factor of two alternators operating in parallel, the ()Afield excitation of both units is adjustedBgovernors of both units are adjustedCphase sequence is alteredDkilowatt load is evenly divided

单选题A constant output voltage from an AC generator is maintained by the ().Aprime mover governorBexciter generatorCvoltage regulatorDreverse power relay