Pass Benchmark: 70% (21/30) • Standard: USCG NMC / 46 CFR

USCG Marine Electrical Systems (Set 4)

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Question 1 of 30

How are AC and DC generators are similar?

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30 MCQs

#1 How are AC and DC generators are similar? #2 By what means is a diesel driven emergency generator prevented from being paralleled with the ship's service generators? #3 As shown in the illustration, which brush holder would be appropriate to use in a bi- directional motor? Illustration EL-0029 #4 Upon failure of the ships normal electrical power supply, by means of what device does the emergency generator supply power to the emergency switchboard, but not the main switchboard? #5 What is the main purpose of an electric space heater installed in a large AC generator? #6 When shore power is being connected to a ship in dry dock, what must be ensured, assuming that the ship's generators are rated at 450 VAC, 60Hz with a total capacity of 5000 kW? #7 With what device is the RPM of an AC generator indirectly measured on a switchboard when operating singly (no other generator connected to the bus)? #8 What does the amount of voltage induced in the stator windings of a modern AC generator mainly dependent upon? #9 A DC generator which is used to supply direct current in order to provide magnetizing current to an AC generator field is commonly known as what? #10 In which figure shown in the illustration will the highest voltage be induced? Illustration EL-0028 #11 When would be the safest time to close the ship's main switchboard "shore power" circuit breaker? #12 How are the number of cycles per second developed by the alternator aboard your vessel determined? #13 The governor control switch of an alternator is moved to the 'raise' position. What will be the effect of this action? #14 How is the power factor of an AC generator operating singularly determined? #15 Prior to manually starting an AC generator prime mover and paralleling in the manual control mode, what should be the position of the voltage regulator selector switch? #16 How is the frequency of an alternator at a given RPM determined? #17 Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. How are these changes in armature reaction compensated for? #18 What is the most practical way to control the voltage output of an AC generator? #19 How will the value of the output frequency change if the load is removed from a turbo generator having a governor speed droop setting of 3%? #20 When securing an AC generator, what should be your FIRST action in accomplishing the procedural steps? #21 Which of the methods listed below is used to provide the rotational torque to cause an AC generator to turn? #22 What devices maintains equal power factors on paralleled AC generators automatically? #23 Attempting to parallel an AC generator which is out of phase with the bus will result in which of the following conditions? #24 You are attempting to parallel two AC generators and the synchroscope pointer is revolving in the fast direction. What is the frequency of the oncoming generator relative to the bus frequency? #25 Which of the following statements is true concerning the operation of two alternators in parallel? #26 When paralleling two alternators using three synchronizing lamps, the flickering of all three lamps becomes progressively slower and slower. What does this mean? #27 Two AC generators of the same capacity are operating in parallel. One with a zero speed droop setting and the other with a 5% speed droop. If its capacity is not exceeded, what will be the characteristic of the unit whose governor has the zero speed droop setting? #28 What device is used so that the kilowatt load sharing can be adjusted on paralleled generators? #29 If the excitation of an alternator operating in parallel is decreased below normal and the other above normal, what will be the result on the alternator with the excitation decreased below normal? #30 You are paralleling two alternators. The synchronizing lamps grow dim and are totally darkened as the synchroscope pointer approaches the 0° position. What does this indicate?

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