Pass Benchmark: 70% (21/30) • Standard: USCG NMC / 46 CFR
USCG Marine Electrical Systems (Set 42)
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Question 1 of 30
A shown in figure "A" of the illustrated propulsion motor variable speed drive, what statement is true? EL-0140
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30 MCQs #1 A shown in figure "A" of the illustrated propulsion motor variable speed drive, what statement is true? EL-0140 #2 How is the speed of the propeller shaft directly coupled to an AC synchronous drive motor changed when powered by either a dedicated or integrated constant frequency alternator in an AC diesel-electric drive system? #3 A common method used to control the speed of a synchronous AC propulsion motor on a diesel-electric propulsion drive is by what means? #4 As shown in the illustrated electric propulsion control scheme for a twin screw vessel, when the two shaft speeds are within 5% of each other, the bridge may select "shaft synchro-phasing mode". What statement is true regarding the purpose of this operating mode? EL-0168 #5 Which of the listed temperature measuring devices installed on a large turbo-electric alternating current propulsion generator would be the most reliable for monitoring generator temperatures to avoid premature winding insulation failure? #6 Which of the listed devices is most likely to be installed on a large modern diesel- electric alternating current propulsion generator for commercial ship propulsion for the purposes of fire suppression? #7 Propulsion AC generators creating 4160 VAC use transformers to provide nominally 120 VAC to the automatic voltage regulator. What is the turns ratio of this step-down transformer? #8 An electric propulsion drive system in which the propulsion generator supplies power to both the propulsion motor and ship service loads is referred to as what type of system? #9 An electric propulsion drive system in which the propulsion generator only supplies power to the propulsion motor is referred to as what type of system? #10 In addition to improper brush pressure or seating, what can result in excessive sparking at the brushes of a DC propulsion motor? #11 Which of the listed temperature measuring devices installed on a large turbo-electric alternating current propulsion generator would be the most reliable for monitoring generator temperatures to avoid premature winding insulation failure? #12 While standing an "at sea watch" onboard a modern rectified DC diesel-electric drive ship you notice the transformer core temperature slowly rising. What should be your FIRST action? #13 While standing an "at sea watch" onboard an AC diesel-electric drive ship with a synchronous propulsion motor, you notice that the kwatt load is at roughly 75% of capacity with a leading power factor less than 1. Ideally what would be the character of the power factor associated with the main power distribution including all motors? #14 On a vessel with turbo-electric drive, which of the following conditions would indicate that the propulsion motor had dropped out of synchronization with the propulsion generator? #15 What equipment for modern SCR rectified DC propulsion drive systems is usually included in the package? #16 Power conversion for use in DC propulsion drive motors is accomplished by what type of converter? #17 As shown in the illustration of a DC diesel-electric propulsion drive system, what would be the set-up contactor configurations if #1 M/E is to be secured, so that only #2 M/E diesel- generator is set up to supply both propulsion motors? EL-0141 #18 How are fuses usually rated? #19 Due to the operating characteristics of the system, time lag fuses (or dual-element fuses) are necessary for use in what types of circuits? #20 What is the characteristic that is associated with an "instantaneous-trip" single- element type fuse? #21 Fuses are sometimes placed in series with a thermal trip-type circuit breaker. What is the purpose of a fuse used in this arrangement? #22 In a dual element time-delay cartridge-type fuse, what type of protection is provided for motor applications? #23 A fuse is the most common type of protection against a short-circuit fault in LV distribution circuits, motor circuits and for portable appliances. What is a major drawback or deficiency with the use of fuse? #24 By what means does a molded-case breaker provide protection against short circuits? #25 As shown in figures "E" and "F" of the pictured high voltage rack mounted circuit breaker, which figure represents the circuit breaker position when in the open or tripped position? Illustration EL-0167 #26 When the operating handle of a molded-case circuit breaker is in the mid-position, what does this indicate? #27 As shown in the illustration, which of the following pieces of equipment is supplied with a circuit breaker providing both overload and short-circuit protection? EL-0165 #28 What is a bus disconnect link used to isolate? #29 What is meant by the term 'dielectric'? #30 What is the greatest single cause of electrical failures?
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