connected load
prime mover speed
field excitation
generators rated voltage
第1题：
The frequency of an AC generator is controlled by the ___.
A.rheostat
B.governor
C.exciter
D.capacitor
第2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 generator
B.the alternating current generator
C.the exciter
D.the prime mover
Which of the following statements is true according to the passage ?
A.With a purely resistance load, the power factor is zero
B.Inductive loads combined with resistance loads produces leading power factors
C.Capacitive loads combined with resistance loads produces lagging power factors
D.With a purely resistance load, the phase angle is zero
When 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 much
B.there is a considerable voltage drop in the capacitive load combined with resistance load
C.when the load is the capacitive load combined with resistance load, the voltage drops to zero
D.when the load is the inductive load combined with resistance load, the voltage drop is fairly large
The exciter must vary with: ① load current ② the power factor, ③ speed change of the prime mover.A.①
B.②
C.①②
D.①②③
请帮忙给出每个问题的正确答案和分析，谢谢！
第3题：
When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is _____.
A.lagging
B.leading
C.maximum
D.minimum
第4题：
neutralize armature reaction
conduct electric current to an outside circuit
convert DC current to AC current
provide excitation to a DC generator
第5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).
第6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.generator's rated voltage
第7题：
英译汉：power factor
第8题：
The frequency of an AC generator is controlled by the
A.rheostat
B.governor
C.exciter
D.capacitor
第9题：
第10题：
rotor
stator
exciter
armature