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

USCG Marine Electrical Systems (Set 9)

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Question 1 of 30

What is the primary purpose of the brushes of DC generators?

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30 MCQs

#1 What is the primary purpose of the brushes of DC generators? #2 Why are modern DC generators fitted with commutating poles? #3 Why are armature cores in a DC generator made of laminated steel sheets? #4 Which of the diagrams shown in the illustration depicts the proper method of aligning brushes on a commutator for a DC machine? Illustration EL-0057 #5 Which of the following statements is true concerning the following illustration? Illustration EL-0028 #6 As shown in the illustrated DC machine which is configured as a generator, what type of machine is illustrated in terms of the configuration of the windings? Illustration EL-0052 #7 As shown in the illustration, which brush holder is of the reaction type? Illustration EL-0029 #8 By what means is DC generator output voltage decreased? #9 Which of the terms listed best describes a compound-wound DC generator having a higher voltage at no load than at full load? #10 Prior to closing the circuit breaker when paralleling two DC generators, what must you be certain of? #11 By what means is an AC generator prevented from becoming motorized? #12 When two generators are on the line and are both connected across a shared load, how are they said to be operating? #13 What function does an equalizing connection between two compound-wound DC generators operating in parallel serve? #14 To effectively clean a commutator in good physical condition, what should be used? #15 How may propulsion DC motor brush pressures be calculated? #16 Brushes in a DC generator must be positioned in the neutral plane to avoid excessive sparking associated with the brushes. What device is used to prevent the shifting of the neutral plane due to armature reaction for varying generator loads. #17 What can cause uneven wear of the commutator surface on a direct current generator? #18 Hysteresis is one cause of electrical power loss associated with electricity generation equipment. What phenomenon results in hysteresis? #19 What may cause brush sparking in a DC generator during commutation? #20 The counter EMF of a DC motor is maximum when the __________. #21 In terms of voltage potential and current sources, how are shunt wound, series wound, and compound wound DC motors designed to operate? #22 If overloading an electric motor becomes necessary in an emergency situation, what should be done to prevent damage to the motor while allowing sustained operation? #23 What is the name of the DC motor speed control method utilized as shown in figure "B" of the illustration? Illustration EL-0101 #24 In D.C. motor construction, where are the commutating windings wound? #25 What is the function of the commutator associated with a DC motor? #26 What is the characteristic of the mica used in the commutators of DC machinery? #27 In D.C. motor construction, with regard to the individual armature coils' ends, which statement is true? #28 What is the item referred to as a pigtail on a DC motor brush rigging? #29 What is the function of the interpoles installed in DC motors? #30 Which of the following types of DC motors is considered to produce the highest starting torque?

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