Description : During its operation, loud buzzing and resultant welding of contacts of a magnetic relay may be caused by __________. A. overheating of the contactor coil B. low voltage on the operating coil C. low insulation resistance to ground D. lubrication of the contact bearing points
Last Answer : Answer: B
Description : The main difference between a motor control circuit containing low voltage protection and low voltage release is that the latter contains _____________. A. a magnetic operating coil B. normally open line contacts C. thermal-overload protection D. a momentary-contact start button
Last Answer : Answer: D
Description : If a magnetic controller contactor fails to pick up when the coil voltage is applied to the contactor coil, the cause may be _____________. A. overload B. misalignment of the affected contactor contacts C. low spring pressure D. an open contactor coil
Description : In the illustrated motor controller, the motor fails to start. A voltmeter reading between 1 and 6 reads line voltage, while the voltmeter reading between 2 and 6 reads 0 VAC. The problem is __________. EL- ... in the 'M' coil, 'Ma' contact/start switch or overload contacts D. fuse '10a' is blown
Description : If a transformer is connected to a DC source, the transformer will overload at the ____________. A. contacts B. primary coil C. secondary coil D. core
Description : The type of control circuit that will not permit automatic restarting after power is restored, following a power failure is called _____________. A. low voltage protection B. low voltage release C. overload lockout D. reduced voltage restart
Last Answer : Answer: A
Description : A loud buzzing noise in an AC controller is probably caused by _____________. A. poor contact with the overload relay B. an incorrectly sized heater C. a broken shading coil D. abnormal starting current
Last Answer : Answer: C
Description : When an operating motor is connected to the controller shown in the illustration, the a path of current flow through the circuit is ____________. EL-0010 A. 'L1', stop button, start button, coil 'CR', 'L2' B. 'L1' ... L2' D. 'L1', stop button, start button, 'CR' contact, 'M' contact, 'CR' coil, 'L2'
Description : The purpose of a main switchboard circuit breaker's reverse-power trip is to _____________. A. prevent main circuit overload B. protect the circuit breaker blowout coil C. prevent alternator motorization D. prevent low voltage tripout
Description : Low voltage releases as used in some shipboard motor starter and control equipment will have which of the following characteristics? A. They trip circuit contactors when the motor starts to overspeed. B. ... coil of the starter. D. They allow the motor to restart upon restoration of normal voltage.
Description : A loud buzzing noise coming from the contacts in a magnetic controller can be caused by ____________. A. excessive current B. excessive magnet gap C. bouncing of contacts D. dirt on magnet faces
Description : Magnetic controller contacts may become welded together during operating conditions as a result of _____________. A. high spring pressure B. high ambient temperature C. an open coil D. low voltage on operating coil
Description : When troubleshooting a magnetic controller, it is found that the contacts are welded together. The most probable cause is _____________. A. excessive operation at low load B. high ambient temperature C. low voltage on the operating coil D. high voltage on the operating coil
Description : The 'reset' contacts of the master switch shown in the illustration provides the winch controller with ___________. EL-0102 A. low voltage release B. overload protection C. low voltage protection D. high power factor correction
Description : Which of the following statments is true of the illustrated motor controller? EL-0023 A. The low speed is used for starting the motor and when the controller automaticly shifts to High speed. B. The HOL relay ... D. If the overload relay opens for high speed the motor can still be run in low speed.
Description : To stop the electric motor shown in the illustration, the stop button is depressed, causing ____________. EL-0012 A. coil 'MS' to become de-energized B. contacts 'CR1' and 'MR4' to open C. contacts 'MR1', 'MR2', and 'MR3' to open D. contacts 'MS1', 'MS2', and 'MS3' to open
Description : If you hear a loud buzzing noise coming from a magnetic motor controller, you should ____________. A. assume that the motor is operating at a full load B. assume that the controller is operating normally C. ... of the problem D. feel the outside of the casing with your hand to see if it is hot
Description : Where automatic restart does not present a hazard after a power failure, Coast Guard Regulations (46 CFR) require motor controllers for auxiliaries vital to the propelling equipment to be provided ... overload protection B. low voltage protection C. low voltage release D. reverse current protection
Description : Excessive humming of AC contactors may be caused by ______________. A. burnt arc shields B. shorted armature coils C. a broken shading coil D. high voltage
Description : 'A-1', as shown in the illustration, is/are ____________. EL-0017 A. normally-closed overload relay contacts B. a double pole knife switch C. normally-open overload relay contacts D. a single pole knife switch
Description : When power is restored after a complete power failure, a steering gear pump motor will ____________. A. have to be restarted B. have to be reset C. restart automatically D. trip its overload relays
Description : During start-up of the circuit shown in the illustration, it is noted that the ends of component 'C' alternately glow and become dark without the tube illuminating. The most probable cause ... start the lamp D. component 'B' contacts are opening and closing thus prohibiting sufficient current flow
Description : When insulation failure produces a low resistance current path between two conductors, the resulting condition is known as ____________. A. an open B. a short circuit C. a ground D. a surge
Description : The purpose of a magnetic relay is to _____________. A. open a circuit only in the event of overload B. remotely open and close contacts C. provide overcurrent protection during starting D. relay voltages at increased power
Description : A loss of field excitation to an AC generator while operating in parallel will cause it to ____________. A. absorb more and more load due to decreased armature reaction B. lose its load due to ... polarity D. lose its load, begin to motorize, trip out on reverse power relay, and possibly overspeed
Description : During maintenance of circuit breakers, _______________. A. always smooth roughened contact surfaces with a file B. never pass more than rated breaker current through the overload heater element C. ... wear and misalignment of main contacts D. assume heater elements installed are of correct size
Description : The arc resulting from the tripping of a circuit breaker is prevented from damaging the contacts by _____________. A. designing the contacts to open slowly B. directing the arc into an ... an inverse timed thermal trip for short circuit currents D. instantaneous magnetic trip for overload currents
Description : The contacts operated by the D.C. relay coil shown in the illustration are located in the schematic diagram prints at coordinates ____________. EL-0100 A. '41Y' on this page B. '52M52M' and '52H35M' C. '57R' on this page D. '52N' on page '57R'
Description : If the contacts of a motor starter or controller fail to drop out when the 'stop' button is depressed the ____________. A. contacts are carrying excessive current B. contacts have become welded together C. shading coil is broken D. shading coil is loose
Description : A loud buzzing noise at the contacts of a magnetic controller could indicate _____________. A. weak contact spring pressure B. misalignment of the magnet faces C. excessive line current D. mechanical binding
Description : An open shunt field in a direct current machine may be located by connecting the field circuit to an external power source, equal to the rated field voltage or less, and tested with a voltmeter from ... C. any suitable ground to any available line lead D. any field pole to each field coil lead
Description : Three factors responsible for the change in voltage as load is applied to an AC generator are: 1) the drop in resistance in the armature circuit, 2) the change in flux, and 3) the ____________. A. armature winding speed B. inductance load drop C. coil pitch factor D. armature reactance voltage drop
Description : Shading coils are installed on AC full-voltage starters to _____________. A. eliminate contact chatter B. dissipate opening contact arcs C. delay current build up in the holding coil D. protect the motor windings from momentary starting current overload
Description : The schematic diagram shown in the illustration uses symbol 'A' to represent a/an _________. EL-0011 A. non-renewable fuse link B. circuit breaker coil C. overload relay coil D. thermal overload heater
Description : The winch shown in the illustration will not operate in any speed in the lowering direction and at an abnormal speed in 'first point hoist'. The possible cause is that _______________. EL-0102 A. ... '1M' in the power circuit are badly corroded D. master switch contacts 'MS6' have weak springs
Description : In the illustrated motor controller circuit, which statment is true? EL-0023 A. The high and low speed lights operate at less than line voltage with a resistor in series. B. This controller can be ... . The wattage of the high speed light must be greater than the wattage of the low speed light.
Description : If a synchronous motor begins to vibrate severely and pull out of synchronism, the cause may be ____________. A. an overload B. an open in the field coils C. no exciter voltage D. all of the above
Description : After turning on the fluorescent lamp shown in the illustration, you note that the ends of the tube alternately glow and becomce dark without illuminating the center. The most obable cause for ... the lamp D. component 'B' contacts are opening and closing thus prohibiting sufficient current flow
Description : The illustration shows a fluorescent light fixture. The ends of the lamp alternately glow and become dark, but the tube will not light. The most probable cause is that ____________. EL-0081 ... start the lamp D. component 'B' contacts are opening and closing thus prohibiting sufficient current flow
Description : Voltage failure of an AC generator may be caused by ____________. A. failure of the exciter generator B. a tripped bus circuit breaker C. high mica segments on the stator bus bar D. excessive prime mover speed
Description : As shown in the illustration, which listed action will occur first when push button 'Q' is depressed? EL-0017 A. Contacts 'H-1', 'H-2' and 'H-3' close. B. Contact 'H-4' closes. C. Operating coil 'C' energizes. D. Switch 'R' opens.
Description : If the motor shown in the illustration will not start when 'Q' is depressed, which of the listed components should be checked FIRST? EL-0017 A. Fuses 'F-1' and 'F-2'. B. Operating coil 'C'. C. Contacts 'H-1', 'H-2', and 'H-3'. D. Contact 'H-4'.
Description : A shading coil used in an AC magnetic controller, functions to _____________. A. reduce vibration and noise in the contactor B. prevent flux buildup in the operating coil C. eliminate arcing when the contacts close D. energize the operating coil and 'pull in' the contacts
Description : As shown in the illustration, a 'pitch cutback' feature is incorporated in the system. This circuit reduces pitch amount to prevent engine overload when it senses ____________. EL-0095 A. pitch error of ... servo' C. excessive propeller speed or fuel to either engine D. only one engine on the line
Description : The purpose of the capacitor within component 'B' of the circuit shown in the illustration is to ____________. EL-0081 A. prolong the life of the component's contacts B. discharge the neon within ... the inductive reactance in the circuit D. store power to operate the circuit should 'D' open
Description : A transformer in an electric circuit serves to ____________. A. generate its own electrical power B. transform electrical energy into mechanical energy C. increase or decrease circuit voltage as required D. convert AC current to DC current
Description : The 'function generator' of the control circuit illustrated _______________. EL-0095 A. can be programmed to produce a non-linear output for a linear input depending on operating conditions B. is used for ... which or how many engines are needed for a required vessel speed D. all of the above
Description : If a magnetic controller relay fails to drop out when the coil voltage is removed from the relay, the probable cause may be _____________. A. excessive spring tension B. overvoltage C. excessive current D. welded contacts
Description : When the circuit shown in the illustration is operating correctly, the voltage at the reference electrode will be kept in the optimum range of ____________. EL-0090 A. 0.01 - 0.05 volt B. 0.80 - 0.85 volt C. 35 - 60 volts D. 100 - 115 volts
Description : If a magnetic controller contact fails to pick up when the operating coil is energized, one possible cause may be _______________. A. low spring pressure B. low voltage to the coil C. the residual magnetism of the contact faces D. dirty contact faces