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

USCG Marine Electrical Systems (Set 25)

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Question 1 of 30

What is the main function in the use of a capacitor for starting a single phase motor?

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30 MCQs

#1 What is the main function in the use of a capacitor for starting a single phase motor? #2 As shown in figures "A", "B", "C", and "D" of the illustration, what is the usual means by which the rotation direction of the motor is reversed? EL-0207 #3 What is the main purpose of the auxiliary winding on a split-phase, single-phase motor? #4 What type of rotor is most commonly used in the split-phase family of single-phase motors? #5 Which of the pictured motors within the split phase family of single phase induction motors represents a split phase, resistive start, induction run motor? EL-0146 #6 Within the split phase family of single phase motors, what are the operational characteristics of the motor shown in figure "A" of the illustration? EL-0207 #7 Which statement is true concerning a split-phase induction motor? #8 A shaded-pole motor is a specific type of motor included in what class of motor? #9 What are the operational characteristics of the split phase motor shown in figure "A" of the illustration? EL-0215 #10 Which of the listed motors will operate at the highest RPM, assuming that each operates at the same frequency? #11 Assuming that the 3-phase power source has a phase sequence of A-B-C and that the motor is connected as shown in figure "A", if the motor has a clockwise (CW) rotation, what statement is true concerning the motors connected as shown in the other figures? EL-0156 #12 How is the difference between the synchronous speed of a three phase induction motor and its operating speed correctly expressed? #13 The torque-speed and current-speed curves for a three-phase induction motor with a squirrel cage rotor are shown in figures "A" and "B" of the illustration. Which of the following statements is true concerning the depicted curves? EL-0056 #14 In a three-phase, squirrel-cage type, induction motor, how is the primary rotating magnetic field established? #15 As shown in the two-speed single winding three phase motor connection diagrams illustrated in figure "B", what is the connection scheme associated with low speed operation? EL-0118 #16 What is the characteristic of a wound-rotor induction motor, with a high resistance inserted in series with the rotor winding at startup? #17 As shown in the illustrated wound-rotor induction motor, what statement is true concerning motor lead connections? Illustration EL-0148 Illustration EL-0148: the U.S. Coast Guard has not released this illustration. #18 What type of AC motor would use a rheostat in the rotor circuit to vary the speed of the motor? #19 A degree of control over the speed of a slip ring induction motor can be obtained by what means? #20 Which of the following physical characteristics does a three-phase wound-rotor induction motor possess that a squirrel cage induction motor does not? #21 By what means is a synchronous motor started and brought nearly to synchronous speed? #22 Concerning the operating characteristics of a synchronous motor, what statement is true? #23 Assuming that a three phase synchronous motor is separately excited, what statement is true concerning power supplies? #24 Occasionally a synchronous motor is configured without an external shaft to drive a load. In this case, the sole purpose of the synchronous motor is improving overall power factor of an electrical distribution system. What is the name of the synchronous motor so constructed? #25 Not only can a synchronous motor drive a load with greater efficiency than an induction motor, a fringe benefit of the synchronous motor is the ability for power factor correction. What statement is true? #26 In terms of voltage potential and current sources, how are shunt wound, series wound, and compound wound DC motors designed to operate? #27 How can the direction of rotation of a DC motor be reversed? #28 What is the name of the DC motor speed control method utilized as shown in figure "B" of the illustration? EL-0101 #29 From the instant of start-up, through the acceleration period, and until the motor reaches rated speed, when is the counter EMF produced in the windings of a DC motor 'zero'? #30 Which of the following statements describes what will happen when both the polarity of the field poles, and the direction of current to the brushes of a DC motor are reversed?

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