Pass Benchmark: 70% (21/30) • Standard: USCG NMC / 46 CFR
USCG Marine Electrical Systems (Set 41)
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Question 1 of 30
By what means should motor controller contacts be routinely cleaned?
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30 MCQs #1 By what means should motor controller contacts be routinely cleaned? #2 What item (or items) constitute routine AC motor controller maintenance? #3 Before working on an electric cargo winch master switch or controller, what should be done? #4 What damage may occur to the components of a winch master control switch, if the cover gasket becomes deteriorated? #5 Using the illustrated catalog number selection chart, determine the correct catalog number for a motor starter that meets the following selection criteria: a 3-pole, vertically mounted, NEMA reversing starter with an open enclosure rated at 45 continuous amperes, fitted with an electronic overload relay with a ground fault feature set and an operating coil rated at 24 VAC/60Hz. EL-0180 #6 As shown in the illustration, what is the purpose of the Time Delay (TR) coil in the circuit? EL-0104 #7 If the contacts of a motor starter or controller fail to drop out when the 'stop' button is depressed, what could be the cause? #8 What may cause magnetic controller contacts to become welded together during operation? #9 As shown in figure "A" of the illustration, if in troubleshooting the control circuit using on-line techniques with a voltmeter with the start button depressed and the following readings are taken, what is the problem? "X1" to "X2" reads 115 VAC; "1" to "X2" reads 0 VAC; "2" to "X2" reads 0 VAC; and "3" to "X2" reads 0 VAC. EL-0123 #10 As shown in the illustration, what mechanism will disconnect the motor from the line in case of a sustained motor overload? EL-0080 #11 The motor starts when the start button in the illustration is pushed, but stops when the button is released. What is most likely the trouble? EL-0007 #12 In the illustrated motor controller, the motor fails to start. A voltmeter reading between 1 and 5 reads line voltage, while the voltmeter reading between 2 and 5 reads 0 VAC. What is most likely the problem? EL-0007 #13 If a digital multimeter is set up as shown in figure "A" of the illustration to test an AC contactor coil, what would the display read if the coil is open-circuited? EL-0214 #14 As shown in figure "A" of the illustration, what is the primary reason that the propulsion transformers are configured differently so as to produce a 30 degree phase shift in the pulses between the two synchroconverters supplying separate stator windings? Illustration EL-0160 #15 Power conversion for use in DC propulsion drive motors is accomplished by what type of converter? #16 The conversion of constant frequency power into adjustable frequency power in a modern AC propulsion drive system is commonly achieved through the use of what electronic system components? #17 A shown in figure "A" of the illustrated propulsion motor variable speed drive, what statement is true? EL-0140 #18 What type of electric propulsion system converter is shown in the illustration? EL-0155 #19 As shown the illustration of a cycloconverter for an AC synchronous propulsion motor, what statement is true concerning the operating motor frequency? EL-0157 #20 Which of the following statements is true concerning a large polyphase synchronous main propulsion motor as used in an electric propulsion drive system? #21 Which of the following is a disadvantage of electric drive propulsion systems? #22 What statement is TRUE concerning the Azipod propulsion system? #23 Which of the following statement is TRUE concerning Azipod propulsion systems? #24 As shown in figure "B" of the illustration, what statement is true concerning "regenerating" operation? EL-0162 #25 How is the main shaft rotation on an AC diesel-electric propulsion vessel normally reversed? #26 How is the direction of propeller shaft rotation changed when directly coupled to an AC synchronous motor when driven by a variable frequency alternator in an AC turbo-electric drive system? #27 How is the direction of rotation of the main propulsion motor in a modern AC propulsion drive system reversed? #28 How is the speed of the propeller shaft directly coupled to an AC synchronous propulsion motor changed when powered by a variable frequency alternator in an AC turboelectric drive system? #29 What statement is TRUE concerning the speed of a synchronous ac propulsion motor? #30 By what common means is the speed of the AC propulsion motor on a diesel- electric propulsion ship controlled?
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