网友您好， 请在下方输入框内输入要搜索的题目：
题目内容
（请给出正确答案）
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 （）.
A
is small
B
may be neglected
C
is useful
D
is considerable
参考答案
参考解析
解析：
暂无解析
更多 “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 （）.A is smallB may be neglectedC is usefulD is considerable” 相关考题
考题
Cathodic protection involves supplying electrons to the metal to be protected from an external source. The external source maybe be an external _______ or by__________.
A、dc power sourceB、Alternating Power SourceC、A Galvanic CoupleD、Cathode
考题
In a modern three-phase A.C. synchronous brushes generator, the excitation winding is on the rotor. That means .A.The generator need not excitation.B.The winding on the rotor is for inputting excitation current.C.There are three phase windings on the rotor.D.The generator has no brushes.
考题
Which of the following components are used to convert alternating current produced in the generator windings to direct current?A.Armature and equalizerB.Commutator and brushesC.Rotor and interpolesD.Field and exciter
考题
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！
考题
You are upgrading your Cisco router IOS from a TFTP server over the network. The upgrade procedure is stopped and you are prompted to erase the current flash contents before continuing. What is most plausible reason for this? （）A、There is insufficient room for more than one image.B、The router has detected a copy of the current software image on the TFTP server.C、The file can be relocated and not compressed.D、The image to load is a binary executable file.
考题
单选题The purpose of DC generator brushes is to （）.A
neutralize armature reactionB
conduct electric current to an outside circuitC
convert DC current to AC currentD
provide excitation to a DC generator
考题
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 （）A
rotorB
statorC
exciterD
armature
考题
单选题Generator brushes are staggered to（）A
reduce current pulsationsB
reduce brush chatterC
prevent uneven commutator wearD
allow greater power generation
考题
单选题The instantaneous reduction in voltage of an AC generator, resulting from an increase in load, and prior to the automatic voltage regulator correcting the situation, is called voltage （）.A
droopB
dropC
dipD
regulation
考题
单选题Generators should have an excitation/voltage regulation system which will enable them to share the steady state reactive load （） no machine exceeds its proportional share of reactive load by more than 10% of the rated reactive load of the largest generator.A
whenB
so asC
such thatD
though
考题
单选题When securing an AC generator, you should FIRST （）.A
open the generator circuit breakerB
switch the voltage regulator to “manual”C
decrease the field excitation to minimumD
reduce the load on the unit
考题
单选题Self-excited a-cgenerator with "error operated" voltage control systems draw the full excitation power for the machine terminalsThis dispenses with the current transformers, reactors and capacitors necessary for accurate compounding, but renders the excitation system vulnerable to variations in its output voltageWhich of the following is correct about the generator mentioned according to the sentences above （）.A
It consumes no excitation powerB
It has current transformersC
Components are needed for accurate compoundingD
Its excitation system is vulnerable to voltage variations
考题
单选题In an alternating current electrical system, a low system power factor is a direct sign of （）A
wasted energyB
efficient operationC
a short in the exciter field windingsD
an excessive number of minor system grounds
考题
单选题The frequency of the alternating current generated by a synchronous generator is governed by the speed and the（）A
full excitationB
loadC
power factorD
number of poles
考题
单选题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 phaseB
Current may lead the voltageC
Current may lag the voltageD
All of the above
考题
单选题Which of the following components are used to convert alternating current produced in the generator windings to direct current?（）A
Armature and equalizerB
Commutator and brushesC
Rotor and interpolesD
Field and exciter
考题
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 （）.A
is smallB
may be neglectedC
is usefulD
is considerable
考题
单选题The purpose of the commutator and brushes on a DC generator is to（）A
change AC to DCcurrentB
change DC to AC currentC
neutralize a armature reactionD
carry current to the outside circuit
考题
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（）A
an incorrect diesel generator governor speed droop adjustmentB
a faulty reverse power relay within the main circuit breaker assemblyC
unsynchronized isochronous load distribution adjustmentsD
a different speed setting on each unit
考题
单选题To （） , the power is supplied by main switchboard directly not though sub-board.A
save network costB
improve the reliability of supplying power to important loadC
prevent sequence reverseD
increase the power factor of important load
考题
单选题The initial voltage of self-excitation generator set up by（）A
residual magnetismB
voltage regulatorC
electrical current for excitationD
the other running generator
考题
单选题Which of the following should be the FIRST step in removing a generator from parallel operation?（）A
Trip the generator off the switchboardB
Turn off all electrical equipmentC
Remove the load from the off going generatorD
Increase the cycles of the generator staying on the line
考题
单选题Current changing in direction and rising and falling in value is （）.A
ACB
DCC
generatorD
fresh water generator
考题
填空题Nikola Tesla invented alternating current technology that enabled electricity to be transmitted over long distances.____
考题
单选题A vessel is equipped with two ships service generatorsGenerator #1 is rated at 900kw and generator #2 is rated at 600kw.During parallel operation, with a hotel load of 1000kw, what should be the kw load on generator #2 （）.A
100kwB
400kwC
500kwD
600kw
考题
单选题In a modern three-phase A-Csynchronous brushless generator, the excitation winding is on the rotorThat means （）.A
The generator needs not excitationB
The winding on the rotor is for inputting excitation currentC
There are three phase windings on the rotorD
The generator has brushes
热门标签
最新试卷
