4439909
Description
| Question | Answer |
| How can the loss of residual magnetism in an alternator or generator be corrected? | using a storage battery or battery charger to 'flash' the field |
| No.1 SSDG was operating in parallel with No.2 SSDG in supplying the 480 VAC main bus while sharing the electrical load evenly. As a result of a problem, if No.1 SSDG begins to motorize, but the generator has not yet tripped out by the action of the reverse power relay, what would be the indication of this? | The kilowatt meter of No.1 SSDG would indicate a negative wattage (a reversed reading). |
| On a steamship, if No.1 SSTG fails to produce a voltage while in the automatic voltage control mode, but successfully produces a voltage while in the manual control mode, what statement is true? | The voltage failure would most likely be the result of a failed voltage regulator. |
| If a shipboard AC generator experiences a failure to produce a voltage, what may be the cause? | an open in the rotor field circuit |
| Ships requiring rapid maneuvering response with a high degree of main propeller shaft control are most often what type of drive system? | Diesel-electric drive |
| 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? | an integrated system |
| 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? | Temperature sensors inserted in the stator slots for measuring stator winding temperature. |
| Which statement is TRUE concerning electric propulsion drives? | The propeller speed and direction of rotation are easily controllable. |
| What is one major advantage of a diesel-electric propulsion plant? | excellent maneuverability |
| Which of the following is a disadvantage of electric drive propulsion systems? | Propulsion motors are required along with electrical power generation machinery. |
| The arc resulting from the tripping of a circuit breaker is prevented from damaging the contacts. How is this done? | directing the arc into an arc chute |
| What is the basic similarity between a circuit breaker and a fuse? | after a short or overload condition, both should open to de-energize the circuit |
| A thermal-magnetic circuit breaker for a 300 kW alternator is rated at 500 amperes at full continuous load. Which of the following conditions will trip the breaker? | Instantaneous current draw of 5,000 amperes. |
| By what common means is the speed of the AC propulsion motor on a diesel-electric propulsion ship controlled? | by varying the input frequency of the voltage to the motor |
| 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? | unity |
| The propulsion motor most often utilized in an AC drive system operating in the moderate to high power range is of what type? | synchronous type with wound field |
| How is the main shaft rotation on an AC diesel-electric propulsion vessel normally reversed? | reversing the phase sequence supplied to the motor |
| What is the operating function of a cycloconverter (CCV) as a static power converter used in electric propulsion motor drives? | provides adjustable frequency to power an AC propulsion drive motor |
| Normally, what is the FIRST step in troubleshooting a transistor mounted on a circuit card? | visually inspect the card |
| If both the 'high level' and 'low level' alarms come on for the same address of a centralized control console, what is the most likely failure? | sensor failure |
| A full-wave rectifier has one diode burned out in an open condition, what will be the output characteristic of the device? | Half-wave rectified |
| When troubleshooting an electronic circuit, an unreliable high resistance "cold" solder joint can be located with the aid of an ohmmeter. Once the problem has been located, what should be done? | reheat connection with a soldering tool and recheck with an ohmmeter |
| When testing a capacitor with a digital multimeter set up as an ohmmeter, what would be the indication on the display when testing an initially discharged capacitor in good condition? | the display would immediately show very low resistance but gradually climb to 'OL' |
| Which of the listed statements is correct when using a digital multimeter set up as an ohmmeter? | With the test leads shorted together, a reading of 'zero' ohms will be displayed. |
| If a digital multimeter set up to measure AC volts reads slightly above 'zero' when its leads are disconnected, what is this a result of? | 'ghost' voltages due to electromagnetic energy in the air |
| To determine the state of charge of a nickel-cadmium wet cell storage battery during charging and discharging, what is the most reliable method? | Checking the electrolyte specific gravity in the cells. |
| When troubleshooting a lead-acid storage battery, what is the best method for detecting a weak or dead cell? | comparing the specific gravity of the electrolyte in each cell |
| What could prevent a lead-acid battery from accepting a full charge? | Leaving the battery in a discharged condition for a great length of time. |
| As the electrolyte level in the cells of a lead-acid battery evaporates over time, what will tend to happen to the specific gravity of the electrolyte in the cells as the level drops due to evaporation? | The specific gravity of the electrolyte will increase as only the water will evaporate from the electrolyte solution. |
| What condition associated with a lead-acid battery cell can cause the plates to partially short-out and cause the cell to fail to hold a charge? | accumulation of sediment within the cells due to excessive overcharging and discharging |
| What would be the synchronous speed of a 24-pole three-phase synchronous motor operating at 20 Hz? | 100 rpm |
| If a 12-pole three-phase synchronous alternator is operating at 590 rpm, what will be its output frequency? | 59 Hz |
| What would be the actual rotor speed for a 4-pole three-phase squirrel-cage induction motor operating at 60 Hz if the rotor slip is 3%? | 1746 rpm |
| What would be the synchronous speed of an eight-pole three-phase squirrel-cage induction motor operating at 60 Hz? | 900 rpm |
| A six-pole three-phase squirrel-cage induction motor operating at 60 Hz is running at 1155 rpm. What is the percentage slip in this case? | 3.75% |
| A voltage amplifier has a calculated voltage gain of 5. Which statement is true concerning input and output voltages? | If the input changes 2 volts, the output changes 10 volts. |
| How are operational amplifiers, used primarily in analog circuits, characterized? | high input impedance, high gain and low output impedance |
| In an azipod propulsion system, how is three phase, frequency and voltage controlled power delivered to the synchronous propulsion motor stator windings? | By the use of slip rings and brushes. |
| Which of the following statement is TRUE concerning azipod propulsion systems? | The system integrates propulsion and steering into one function. |
| In an azipod propulsion system, how is direct current delivered to the synchronous propulsion motor rotor for synchronous operation? | By the use of slip rings and brushes. |
| What statement is TRUE concerning the azipod propulsion system? | It is an electric drive system where the propulsion motor is installed in a submerged housing capable of swiveling. |
| In an azipod propulsion system, how is the azipod unit itself rotated for the purposes of directing the thrust in accordance with steering commands from the bridge? | The azipod drive unit is rotated by means of a hydraulic steering unit. |
| What is a disadvantage to the use of high voltage systems onboard ship? | Necessary adherence to stringent safety procedures |
| Some shipboard high voltage systems have the neutral point of the generators bonded to the ship's hull with a neutral grounding resistor. What is the purpose of this resistor? | To minimize the magnitude of the ground fault current |
| Before work may safely commence on a high voltage system, what must first be done after disconnection and isolation? | The circuit must be tested and proved dead first with a live-line tester, then grounded. |
| Suppose it is desired to determine the integrity of the insulation of a 4160 VAC motor. What type of insulation resistance tester (megger) would be suitable? | 5000 V megger |
| For the purposes of high voltage marine practice, what is the threshold voltage where all voltages below this value are considered low voltage? | 1.0 kV |
| In addition to high voltage circuit grounding with ground-connecting switching devices, for additional operator safety and confidence, portable grounding straps may be used. What is the proper procedure for connecting these portable grounding straps? | Connect the common connection to hull ground first, then connect the phase connections to common. |
| When completing repairs on a high voltage circuit where portable grounding straps were used for increased operator safety and confidence, what is the proper procedure for disconnecting these grounding straps? | Disconnect the phase connections to common first, then disconnect the common connection to hull ground. |
| In order for a live-line tester to be used to test and prove dead a high voltage circuit, what must be done to verify the ability of the tester to detect a voltage? | The live-line tester should be checked by connecting to a known high voltage source before and after the circuit to be worked upon is tested. |
| What is the most common and reliable type of circuit breaker used for high voltage practice aboard ship? | vacuum-break |
| For a motor rated at 3.3 kV, what would be a minimum accepted insulation resistance to hull ground as tested by an appropriate megger (insulation tester)? | 4.3 megohms |
| If it becomes absolutely necessary to run an alternator at lower than 5% below its rated frequency, in terms of output voltage, what must be done? | The alternator output voltage must be decreased proportionately downward with the frequency decrease. |
| Upon loss of field excitation of a generator operating in parallel with others, what must be done? | The parallel-connected generator which has suffered the loss of field excitation must be immediately disconnected from the bus by tripping its circuit breaker. |
| Under unusual circumstances, it may be required to operate a ship's service generator above its rated kVA. What supplemental casualty control action will be required? | Increase the cooling water flow, while maintaining air temperatures above the dew point to avoid any condensation. |
| When a self-excited alternator's field has lost its residual magnetism due to a prolonged idle period, it will fail to produce a voltage. Flashing the field is the procedure used to restore the residual magnetism. Using a 12 volt storage battery, how is this performed? | The F+ and F- leads are disconnected from the alternator field. The F+ lead is connected to the positive terminal of the battery, and the F- lead is connected to the negative terminal. |
| What is the name of the semiconductor that decreases in resistance with an increase in temperature? | thermistor |
| In what applications are germanium semiconductor diodes commonly used? | rectifiers |
| In comparing a semiconductor diode to a vacuum tube diode, what statement is true? | The semiconductor diode has longer life, no warm-up time, and is less delicate than the vacuum tube diode. |
| A silicon controlled rectifier (SCR) is a solid state device used for what functional purpose? | functions like a switching device and controls relatively high load current |
| Which of the following statements correctly applies to bipolar junction transistors? | The three terminals are called the emitter, base, and collector. |
| An AC circuit has a capacitive reactance of 30 ohms in addition to an inductive reactance of 40 ohms connected in series. What is the total reactance of the circuit? | 10.00 ohms |
| How should the shunt used in an ammeter be connected? | in series with the load and in parallel with the meter movement |
| What is an ammeter used to measure? | current flow in a circuit |
| To properly use a clamp-on-type ammeter to check current flow, what must be done FIRST? | hook the jaws of the instrument around the insulated single conductor |
| The clamp-on AC ammeter consists essentially of a split-core and a rectifier-type instrument connected to the secondary winding of a particular type of transformer. Which type is used? | current transformer |
| Why are external shunts sometimes used with ammeters? | to prevent damage to the meter movement from heat generated by the internal shunt |
| Prior to closing the circuit breaker when paralleling two DC generators, what must you be certain of? | voltage of the incoming machine is at or slightly above the bus voltage |
| Which of the methods listed is used to maintain equal load sharing between two compound wound DC generators operating in parallel? | The series fields of both generators are connected in parallel. |
| With what device is the simplest method of controlling the terminal voltage of compound wound DC generator? | hand-operated field rheostat connected in series with the shunt field circuit |
| By what means is a DC generator prevented from becoming motorized if paralleling is accomplished without an equalizer? | reverse current relay |
| 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? | Excessive vibration of the vessel |
| 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? | check the transformer ventilation fans for proper operation |
| In addition to improper brush pressure or seating, what can result in excessive sparking at the brushes of a DC propulsion motor? | improper positioning of brush rigging outside the neutral plane |
| Silicon diodes which are designed for a specific reverse breakdown voltage, and are most often used as electronic power supply voltage regulators, are specifically what type of diode? | Zener diodes |
| A common-emitter circuit has an input voltage of 0.1 volt, an output voltage of 2.0 volts, an input current of 0.5 milliamps, and an output current of 10 milliamps. What is the power gain? | 400 |
| A signal derived from an amplifier output and returned to the amplifier input is called what type of signal? | feedback signal |
| Which of the following statements represents an application of a silicon controlled rectifier? | Provides DC power for a main propulsion motor. |
| In monitoring an impressed current cathodic hull protection system, it is important to insure that the propeller screw receive the same cathodic protection as the hull. What should be checked for? | Insure adequate grounding carbon brush pressure on the rotating shaft and check brushes for wear. |
| While monitoring an impressed current cathodic hull protection system, which of the following measurements should remain constant in a properly operating electronically regulated system? | Reference electrode voltage |
| In an impressed current cathodic hull protection system, what statement is true concerning the composition and arrangement of the anodes? | The protective anodes are made of lead or platinized titanium and are electrically insulated from the hull. |
| What are the characteristics of the field winding of a shunt wound motor? | The shunt-field coils are wound with many turns of very fine wire. |
| In a shunt wound DC motor, how is the shunt field connected? | The shunt field is wired in parallel with the armature circuit, including armature, commutating, and compensating windings. |
| What type of DC motor has relatively low starting torque, but has excellent inherent speed regulation? | shunt wound |
| What statement is true concerning speed control of a shunt wound DC motor? | For armature rheostat control, the greater the resistance the lower the motor speed. For field rheostat control, the greater the resistance the higher the motor speed. |
| In a series circuit, which value will remain unchanged at all places in the circuit? | Current |
| Four lamps are connected in series in a single circuit. If one of the lamps burns out, what will happen to the other lamps? | all go out |
| In a series circuit what is the total applied voltage equal to? | the sum of the individual voltage drops |
| How is seating of new brushes on a DC motor commutator accomplished? | using fine sandpaper on a de-energized machine between the brush and the commutator to establish the proper curvature |
| In general, what can cause DC propulsion motor brush sparking to be excessive? | incorrect brush grade, pressure or position |
| What should be used in the cleaning of a DC propulsion motor's commutator face? | a canvas wiper |
| Which of the listed conditions will occur if dirt and grease are allowed to accumulate between the commutator segments of a DC motor? | A partial short circuit. |
| DC propulsion motor brush pressure depends on the brush grade used. In practice with what device is the proper brush pressure established? | spring scale |
| In a simple DC circuit, the resistance is held constant while the applied voltage is halved. What will be the effect on the current flow as compared to the original current? | be divided by two |
| A 125 volt DC motor is rated at 10 kW. What is the current rating of the motor? | 80 amps |
| An AC generator produces 60 Hz at 1800 RPM. If the generator speed is increased to 1830 RPM, what will happen to the frequency in Hz? | increase to 61 Hz |
| In a 60 Hz AC system, what is the duration in seconds for one complete cycle? | 0.016 of a second |
| How is the power dissipated as heat in a direct current circuit calculated? | I squared times R |
| An electrical component is connected across a 120 volt 60 hertz AC supply. What is the current drawn by the component if the impedance is 200 ohms? | 0.60 amperes |
| If a DC generator was disassembled during overhaul, it is important that the brush holder rigging be installed in the neutral plane. On larger machines, if the brush rigging and end bells are not match-marked, what is the correct procedure for determining the neutral setting using factory marks? | With the marked armature slots positioned directly under the center of the interpoles, the brushing rigging should be adjusted and clamped so that the brushes are positioned directly over the marked armature bars. |
| As the brushes ride on the commutator of a DC generator, eventually mica ridges will form between the bars causing sparking and chipping of the brushes. When this happens the mica must be undercut. To what depth is the mica undercut? | The mica slots are undercut to a depth approximately equal to the width of the slot. |
| Incorrect brush pressure can result in accelerated brush wear on a DC generator. What statement concerning brush pressure is true? | There is an optimal pressure range that results in minimal brush wear. Brush pressures above the optimal range cause excessive mechanical wear, and brush pressures below the optimal range cause excessive electrical wear. |
| While inspecting the copper commutator bars of a DC generator, you notice a chocolate brown film covering the bars. What should be done? | The film should be left undisturbed. |
| Suppose a cargo vessel of 1600 gross tons or more is fitted with emergency storage batteries for the purpose of supplying emergency lighting and power. According to 46 CFR, Subchapter J (Electrical Engineering), the capacity of the storage batteries is such that they should be able to successfully power the emergency loads for a period of 18 hours. Beginning with fully charged batteries, what is the minimum allowable voltage of the batteries after the 18 hour discharge period assuming a nominal voltage rating of 24 VDC and operating at rated capacity? | 21.1 VDC |
| In accordance with 46 CFR Part 112, a storage battery for an emergency lighting and power system must have the capacity to accomplish which of the following? | close all watertight doors twice and open them once |
| According to 46 CFR, Subchapter J (Electrical Engineering), which of the following statements concerning battery installations is correct? | When power ventilation is required, blower blades must be non-sparking and the system must be interlocked with the battery charger to prevent charger operation unless the ventilation fan is running. |
| Suppose a cargo vessel of 1600 gross tons or more is fitted with emergency storage batteries for the purpose of supplying emergency lighting and power. According to 46 CFR, Subchapter J (Electrical Engineering), the capacity of the storage batteries is such that they should be able to successfully power the emergency loads for a period of 18 hours. Beginning with fully charged batteries, what is the minimum allowable percentage of the voltage rating of the batteries after the 18 hour discharge period assuming a nominal voltage rating of 24 VDC and operating at rated capacity? | 88% |
| You are in the planning stages of replacing a battery charger, where an exact duplicate of the charger to be replaced is not available. Obviously the charger must be suitable for the battery to be charged. According to 46 CFR, Subchapter J (Electrical Engineering), which of the following is a true statement concerning battery chargers? | Battery chargers incorporating grounded autotransformers must NOT be used, and if the charging voltage exceeds 20% of the battery line voltage, automatic protection against reversal current must be provided. |
| The torque produced by a DC motor armature is the multiplication product of two factors, one being the density of the magnetic flux which is dependent upon the field current. What is the other multiplication factor? | armature current |
| 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'? | armature is not yet turning |
| How can the direction of rotation of a DC motor be reversed? | reversing the field or armature connections |
| What is an advantage of DC motors over AC motors? | DC motors offer a more effective means of controlling speed than AC motors |
| 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? | The direction of rotation of the armature will remain the same. |
| In terms of voltage potential and current sources, how are shunt wound, series wound, and compound wound DC motors designed to operate? | constant potential, variable current DC sources |
| If a DC motor has its armature and field connected across a resistor when the motor is disconnected from its power supply, what statement is true? | The motor will slow down by the process of dynamic braking. |
| Which of the following conditions will occur if the brake solenoid coil burns out on a cargo winch with an electrical brake? | The brake will be set by spring force. |
| By what means is the burning of controller contacts due to arcing, when opening, prevented? | magnetic blowout coils |
| Upon failure of the normal power supply, how is the emergency generator placed on the line to feed power to the emergency bus? | automatic bus transfer device |
| According to 46 CFR, Subchapter J (Electrical Engineering) regulations, receptacle outlets at or above what voltage are required to have grounding poles? | The plug on the end of the cord that may be energized when unplugged from the receptacle must be female. |
| According to 46 CFR, Subchapter J (Electrical Engineering) regulations, what is the minimum conductor size associated with a 25 or 30 ampere lighting branch circuit supplying a non- switched cargo-hold light fixture? | 10 gauge |
| How is a wattmeter electrically connected in a circuit? | In series-parallel |
| Which of the following represents a characteristic of an ungrounded electrical distribution system? | Accidental contact between one line and ground does not cause an outage. |
| The timer element of a reverse power relay cannot be energized unless what condition is met? | the power flow is the same as the tripping direction |
| What is the name of the part of the shipboard electrical system used to control the distribution of power to the branch circuits? | main switchboard |
| How will the value of the output frequency change if the load is removed from a turbo-generator having a governor speed droop setting of 3%? | It will increase. |
| Which of the methods listed below is used to provide the rotational torque to cause an AC generator to turn? | Starting of the prime mover. |
| What is the shape of the schematic symbol for an operational amplifier used in an analog circuit? | triangle |
| Which of the following activities occurs during the charging process of a lead-acid storage battery? | The specific gravity of the acid increases. |
| For accuracy purposes, which of the following devices should be used to measure the temperature of a battery electrolyte? | Electronic digital thermometer |
| Which of the substances listed should be applied to battery terminals to help prevent corrosion? | Petroleum jelly |
| Which of the following statements concerning nickel-cadmium batteries is true? | Nickel-cadmium batteries can be stored for a long period of time while still keeping a full charge. |
| What should you be aware of when checking the specific gravity of the battery electrolyte with a hydrometer? | depending on the temperature it may be necessary to correct for temperature |
| What is the best method of determining the state of charge of a lead acid storage battery? | specific gravity of the electrolyte |
| Which of the listed battery charging circuits is used to maintain a wet cell, lead-acid, storage battery in a fully charged state during long periods of disuse? | Trickle charging circuit |
| What statement is true concerning the charging of a 100 amp-hour lead-acid battery? | The initial charging rate should be no greater than 100% of the battery amp-hour rating. |
| What statement is true concerning the actual mixing process and the container used when mixing electrolyte for a lead-acid storage battery? | pour the acid into the distilled water in a glass container |
| Why must caution be exercised during the charging of lead-acid storage batteries? | hydrogen gas is being continuously liberated |
| What statement is true concerning read only memory (ROM)? | ROM is non-volatile memory and the contents of ROM are not lost when the power is removed. |
| What statement is true concerning random access memory (RAM)? | RAM is volatile memory and the contents of RAM are lost when the power is removed. |
| If an 8-bit digital to analog converter (DAC) produces an analog output voltage with a range of 10 volts (0-9 volts), what is the smallest incremental step in voltage that can be generated at the output? | 0.04 volts |
| What Ethernet cabling technology supports the greatest data transfer speeds? | Gigabit Ethernet |
| If a computer display is flickering, how may this be remedied? | Increase the refresh rate |
| What type of local area network physical topology features point-to-point interconnection between all communicating devices and is the least vulnerable to a break in communication? | Mesh |
| Modern ships use multiple computers arranged in a client/server network to perform various shipboard functions. What type of computer network would most likely be used aboard ship? | Wired local area network |
| Which of the following data communication cable types offers the greatest immunity to electromagnetic "noise"? | Fiber-optic |
| Which of the following devices represents primary storage, where the processor is able to directly read instructions and data and directly return results of its computation in fetch/execute cycles? | Random access memory |
| On vessels with AC distribution systems, which of the following statements represents the most difficult problem involved in obtaining a DC potential suitable for use by computer components? | The voltage must be rectified and made ripple free. |
| The ground indicating light on the main electrical switchboard is indicating a ground. What is the best procedure for locating the grounded circuit? | open the circuit breakers on the distribution panel, one at a time, until the lights no longer indicate a ground |
| In an ungrounded distribution system, as compared to a normal indication, what is the indication on a switchboard of a current carrying conductor making an accidental electrical contact with a wiring metal conduit? | totally darkened switchboard ground-detecting light |
| Which of the conditions listed will indicate the need to clean the insulation on the windings of an electric motor? | Higher than normal operating temperature. |
| When you are making a high potential test (megger) on the motor coils of repaired electrical machinery to ground. What would a low resistance reading indicate? | bad insulation |
| Large machines undergoing a resistance insulation testing using a megohmmeter should be discharged to remove any accumulated electrostatic/capacitive charge stored. When should this discharge be performed? | prior to and after conducting the insulation resistance check |
| What is a useful instrument for checking 3 phase AC motor performance by measuring possible unbalanced currents? | clamp-on ammeter |
| You are reconnecting a three-phase induction motor to the supply line. To prevent possible damage to the load, due to the wrong direction of rotation, what should be done? | check the supply line phase sequence and motor rotation with appropriate indicators, then connect correspondingly marked leads |
| How are the field windings of a DC shunt generator connected? | in parallel with the armature windings |
| What is the purpose of the commutator and brushes on a DC generator? | convert the alternating current voltage generated within the armature to a direct current voltage |
| Why are armature cores in a DC generator made of laminated steel sheets? | reduce eddy current losses |
| What is "the voltage per millimeter of insulation thickness that the insulation can withstand without breaking down" called? | Dielectric strength |
| Why is copper often used as an electrical conductor? | is able to pass current with little opposition |
| How is electrical conductor insulation classed? Example: insulation class H | limiting internal hot spot temperature |
| Which of the following materials is a good electrical insulator? | wood |
| Which of the following is the only known perfect dielectric for the purpose of serving as electrical insulation? | vacuum |
| When electrical cables penetrate watertight bulkheads, what must be provided for? | a watertight stuffing tube capable of accepting packing should be employed |
| What happens to the life expectancy of insulation for each 10oC rise in operating temperature? | The life expectancy is halved. |
| Why are large cable sizes often formed as individual conductors comprised of several smaller strands? | obtain the flexibility required for easy handling and reduces skin effect losses |
| How are the line losses in a distribution circuit kept to a minimum? | using higher voltage and lower current |
| With what kind of starting equipment are most three-phase induction motors of five horsepower or less started? | across-the-line starters |
| Autotransformer starters, sometimes called starting compensators, are sometimes used with larger polyphase induction motors. What function do they perform? | they reduce the voltage applied to the motor during the starting period |
| In general, what type of starter would be used to connect polyphase induction motors to full line voltage at the instant of start-up? | across-the-line starters |
| What device can be used to check the calibration of a circuit breaker? | portable low voltage high current testing unit |
| When a fluorescent lamp has reached the end of its useful life, it should be replaced immediately. If not, what condition could the resultant flashing cause? | damaging the lamps starter and ballast circuit |
| Which of the listed pairs of materials make the best insulators? | paper and mica |
| When a megohmmeter is used to test insulation, what condition causes the gradual rise of the pointer reading as a result of continued cranking? | the dielectric-absorption effect of the insulation |
| Emergency generators are required to automatically start upon a loss of normal supply voltage, according to 46 CFR, Subchapter J (Electrical Engineering). In conducting a test of the emergency generator automatic transfer of load function, if the normal system supply voltage is 480 VAC, to what value would the normal source output voltage have to rise to trigger the automatic transfer of emergency loads back to the normal power source? | It would have to rise to a value from between 408 VAC to 456 VAC. |
| According to 46 CFR, Subchapter J (Electrical Engineering), emergency diesel engine starting systems are required to have sufficient capacity to provide power for at least how many consecutive starts? | 6 |
| According to 46 CFR, Subchapter J (Electrical Engineering), which of the following starting aids is the ONLY method allowed to ease the starting of emergency diesel-generator engines? | Thermostatically controlled electric jacket water heaters |
| Emergency generators are required to automatically start upon a loss of normal supply voltage, according to 46 CFR, Subchapter J (Electrical Engineering). In conducting a test of the emergency generator automatic transfer of load function, if the normal system supply voltage is 450 VAC, to what value would the emergency generator output voltage have to rise to trigger the automatic transfer of emergency loads to the emergency generator? | The voltage would have to rise to a value ranging from any voltages between 382.5 VAC and 427.5 VAC. |
| According to 46 CFR, Subchapter J (Electrical Engineering), in response to a loss of normal power or a simulated test, when will the emergency loads automatically be transferred to the emergency diesel-generator? | when the potential from the emergency generator reaches 85 to 95 percent of its normal value |
| Which of the listed motors will operate at the highest RPM, assuming that each operates at the same frequency? | A four-pole synchronous motor under normal load. |
| In a three-phase, squirrel-cage type, induction motor, how is the primary rotating magnetic field established? | application of a three-phase voltage supply to the stator windings |
| How is the difference between the synchronous speed of a three phase induction motor and its operating speed correctly expressed? | slip |
| What can be the cause of excessive heat or burning contacts in an operating motor controller? | loose connections or low contact pressure |
| There are very specific rules that govern the testing of generators found in the appropriate publication incorporated by reference. According to 46 CFR, Subchapter J (Electrical Engineering), which agency publishes the rules for the construction and testing of generators? | American Bureau of Shipping |
| You are in the planning stages of setting the longtime overcurrent trip of a ship's service generator circuit breaker. According to 46 CFR, Subchapter J (Electrical Engineering), what statement is true regarding the criteria for the longtime overcurrent trip setpoint, assuming the generator is capable of being paralleled? | The trip point should not be larger than 115% of the generator rating for a continuous rated machine. |
| You are in the planning stages of setting the instantaneous trip of a ship's service generator circuit breaker. According to 46 CFR, Subchapter J (Electrical Engineering), what statement is true regarding the criteria for the instantaneous trip setpoint, assuming the generator is capable of being paralleled? | The trip point should be set above but as close as practical to the maximum asymmetrical short circuit current available. |
| In accordance with 46 CFR, Subchapter J (Electrical Engineering), each diesel engine driven generator prime mover must have an overspeed device, independent of the normal operating governor. If in testing the overspeed device, what should be the trip point setting in terms of rated speed? | not to exceed 15% above rated speed |
| Assuming that a ship's service generator is directly coupled to the prime mover, what condition must cause a prime mover to automatically shutdown? | Low generator bearing lubricating oil pressure. |
| What material are the plates of a wet cell NiCad storage battery made of? | nickel hydroxide and cadmium oxide |
| Why are nickel-cadmium batteries superior to lead-acid batteries for standby service? | they are able to hold their charge for long periods of time without recharging |
| What is the most reliable and preferred method for determining the state of charge of a wet cell NiCad battery? | Measuring the battery voltage with a digital voltmeter during charge or discharge. |
| What is the approximate discharge voltage produced by one cell of a wet type nickel- cadmium battery at 75% of charge? | 1.2 volts |
| The nominal voltage of one cell of a wet cell nickel-cadmium battery is approximately how many volts? | 1.2 volts |
| According to CFR, Subchapter J (Electrical Engineering), which of the following statements is true concerning flexible electric cord and cable used aboard ship? | No. 12 AWG cable or cord may be spliced for repairs if made in compliance with CFR 111.60- 19. |
| According to 46 CFR, Subchapter J (Electrical Engineering), what statement is true concerning the use of twist-on connectors? | Twist-on connectors may be used in enclosures as long as the insulating cap can be secured to prevent loosening due to vibration. |
| According to 46 CFR, Subchapter J (Electrical Engineering), when considering replacement, instrument and control wiring in a switchboard is to be of what minimum size? | 14 AWG |
| According to 46 CFR, Subchapter J (Electrical engineering), regulations prohibit the use of portable electric cord or fixture wire aboard ship if that wire or cord is smaller than what size? | 18 AWG |
| Electrical wire in general, when used aboard vessels must meet minimum requirements. Which of the following statements is/are correct? | Wire must be of the stranded copper type. |
| 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? | If the overall plant has a unity power factor, the synchronous motor is normally-excited. |
| Assuming that a three phase synchronous motor is separately excited, what statement is true concerning power supplies? | The rotor winding via slip rings and brushes is connected to a DC power source, and the stator windings are directly connected to a three phase AC power source. |
| 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? | Synchronous condenser |
| Concerning the operating characteristics of a synchronous motor, what statement is true? | The synchronous motor initially starts as an induction motor and when it approaches synchronous speed, the motor then runs as a synchronous motor. |
0 comments
Want to create your own Flashcards for free with GoConqr? Learn more.