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competency Quiz on c05a, created by mrk nthny on 14/08/2016.
mrk nthny
Quiz von mrk nthny, aktualisiert more than 1 year ago
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Erstellt von mrk nthny vor mehr als 8 Jahre
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Zusammenfassung der Ressource

Frage 1

Frage
What is the maximum allowable primary current of a 2 KVA step - down transformer with a four to one turns ratio if connected across a 440 volt line?
Antworten
  • 4.5 amps
  • 1.1 amps
  • 18.1 amps
  • 27.7 amps

Frage 2

Frage
The open-circuit voltage of a fully charged lead-acid battery cell is _______ .
Antworten
  • 2.0 volts
  • 2.3 volts
  • 1.5 volts
  • 1.8 volts

Frage 3

Frage
A milliammeter, with a full scale deflection reading of 100 milliamps, is known to have an accuracy of + or - 2%. A meter reading of 10 milliamps would indicate a line current of between.
Antworten
  • 9.8 and 10.2 milliamperes
  • 8.0 and 12.0 milliamperes
  • 9.8 and 10.0 milliamperes
  • 8.0 and 10.0 milliamperes

Frage 4

Frage
Basic electrical motor action depends on_______.
Antworten
  • a current carrying conductor placed in a magnetic field
  • a conductor rotated within a magnetic field
  • the relative force of the commutator and commutating poles
  • the relative force of the armature and interpoles

Frage 5

Frage
What is the function of damper windings in a synchronous motor ?
Antworten
  • DC voltage to the field
  • AC voltage to the armature
  • AC voltage to the field
  • DC voltage to the armature

Frage 6

Frage
The Wheatstone bridge is a precision measuring instrument utilizing the principle of changes in____ .
Antworten
  • resistance
  • amperage
  • inductance
  • capacitance

Frage 7

Frage
"The rated temperature rise of an electric motor is the_______. . "
Antworten
  • normal temperature rise above the standard ambient temperature at rated load
  • average temperature at any given latitude
  • average temperature rise due to resistance at 10% overload
  • permissible difference in the ambient temperature of the motor due to existing weather conditions

Frage 8

Frage
The part of the shipboard electrical system used to control the distribution of power to the branch circuits, is the______.
Antworten
  • main switchboard
  • bridge control panel
  • disconnect links
  • governor relay box

Frage 9

Frage
Voltage generated by most AC generators is fed from the machine to the bus by means of ____ .
Antworten
  • direct connections from the stator
  • brushes on slip rings
  • brushes on a commutator
  • slip rings on a commutator

Frage 10

Frage
Battery charging rooms should be well ventilated because the charging process produces ______.
Antworten
  • explosive gases
  • corrosive gases
  • highly poisonous gas
  • highly combustible oxygen

Frage 11

Frage
Battery charging rooms should be well ventilated because the charging process produces ______.
Antworten
  • explosive gases
  • corrosive gases
  • highly poisonous gas
  • highly combustible oxygen

Frage 12

Frage
When reading electrical motor controller diagrams, it helps to know that________.
Antworten
  • current paths in the power circuit are drawn as heavy lines and in control circuit as lighter lines
  • current paths in the control circuit are drawn as heavy lines and in the power circuit as lighter lines
  • circuits subject to 500 volts or greater are drawn as heavy lines and below 500 volts as lighter lines
  • circuits subject to 500 volts or greater are drawn as light lines and below 500 volts as heavy lines

Frage 13

Frage
A device that utilizes the principle of electromagnetic induction is the______ .
Antworten
  • transformer
  • diode
  • transistor
  • rheostat

Frage 14

Frage
Amortisseur windings are installed in a synchronous motor to_____.
Antworten
  • provide a means for starting
  • eliminate arcing between the stator and the rotor
  • produce a higher power factor
  • reduce eddy current losses

Frage 15

Frage
Which of the following physical characteristics does a wound- rotor induction motor possess that a squirrel cage motor has none?
Antworten
  • Slip rings
  • End rings
  • A centrifugal switch
  • End plates

Frage 16

Frage
In an induction motor, rotor currents are circulated in the rotor by________.
Antworten
  • inductive reaction of the rotating stator field
  • external variable resistors
  • slip rings and brushes
  • an armature and brushes

Frage 17

Frage
Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in armature reaction are compensated by the ________.
Antworten
  • voltage regulator
  • governor speed droop setting
  • balance coil
  • phase-balance relay

Frage 18

Frage
"A low voltage source is being used for testing armature coils. A coil short circuit will be indicated by a ___________. "
Antworten
  • low or zero voltage reading, while the other coils will have higher readings
  • high voltage reading, while the other coil readings will have an equal or lower value
  • fluctuating voltmeter reading, while the other coil readings are steady
  • steady voltmeter reading, while the other coil readings are fluctuating

Frage 19

Frage
When measuring AC current flow, you must always connect the meter ___________.
Antworten
  • in series with the power source and load
  • in parallel with the power source and load
  • insuring correct polarity
  • using the lowest range possible to prevent instrument damage

Frage 20

Frage
To increase the frequency of an operating AC generator, you should __________.
Antworten
  • increase the speed of the prime mover
  • increase the field excitation
  • decrease the field excitation
  • increase the number of magnetic poles

Frage 21

Frage
An electrical device which prevents action from occurring until all other required conditions are met is called _______.
Antworten
  • interlock
  • limit
  • monitor
  • modulator

Frage 22

Frage
The main purpose of the auxiliary winding on a split-phase, single- phase motor is to_______ .
Antworten
  • start the motor
  • limit the starting voltage
  • increase the starting current
  • keep the motor running in the event the main winding should fail

Frage 23

Frage
The heating of conductors as a result of resistance in a distribution circuit causes a power loss expressed as_______.
Antworten
  • line loss
  • line droop
  • IR drop
  • hysteresis

Frage 24

Frage
The greatest detrimental effect on idle electrical equipment, such as cargo pump motor is the_______.
Antworten
  • absorption of moisture in the insulation
  • loss of residual magnetism
  • insulation varnish flaking
  • dirt collecting on the windings

Frage 25

Frage
"An electrical device which employs a stationary armature and a rotating electromagnetic field is used aboard ship as a_______. . "
Antworten
  • ship's service alternator
  • magnetic amplifier
  • three-wire DC generator
  • saturable core reactor

Frage 26

Frage
"A circuit breaker differs from a fuse, in that a circuit breaker_________. . "
Antworten
  • trips to break the circuit and may be reset
  • melts and must be replaced
  • is enclosed in a tube of insulating material with metal ferrules at each end
  • gives no visual indication of having opened the circuit

Frage 27

Frage
AC circuits possess characteristics of resistance, inductance, and capacitance. The capacitive reactance of a circuit is expressed in_____ .
Antworten
  • ohms
  • mhos
  • henrys
  • farads

Frage 28

Frage
The frequency output of an operating alternator is controlled by the______ . .
Antworten
  • relative speed of the rotor poles
  • number of turns of wire in the armature coil
  • strength of the magnets used
  • output voltage

Frage 29

Frage
Which of the following types of motors is often designed for use in correcting power factor?
Antworten
  • Synchronous
  • Polyphase
  • Wound-rotor
  • Induction

Frage 30

Frage
The purpose of a cage rotor winding placed on the rotor of a synchronous motor is to ________.
Antworten
  • start the machine as an induction motor
  • provide excitation to the DC field
  • contribute extra torque at synchronous speed
  • prevent the machine from falling out of step

Frage 31

Frage
A constant output voltage from an AC generator is maintained by the_________.
Antworten
  • voltage regulator
  • reverse power relay
  • exciter generator
  • prime mover governor

Frage 32

Frage
The capacity of a storage battery is measured in_______.
Antworten
  • ampere-hours
  • volts
  • farads
  • amps

Frage 33

Frage
The rated temperature and rise of an electric motor is the ______.
Antworten
  • normal temperature rise above the standard ambient temperature at rated load
  • average temperature at any given latitude
  • average temperature rise due to resistance at 10% overload

Frage 34

Frage
"In an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in armature reaction are compensated by the_______ . . "
Antworten
  • voltage regulator
  • governor speed droop setting
  • balance coil

Frage 35

Frage
What should you do to the charging current when a lead-acid battery gassing freely while receiving a normal charge?
Antworten
  • Reduce
  • Increase
  • Stop
  • No adjustment needed

Frage 36

Frage
External shunts are sometimes used with ammeters to _____.
Antworten
  • prevent damage to the meter movement from heat generated by the internal shunt
  • increase meter sensitivity
  • permit shunts with larger resistance to be utilized
  • reduce reactive power factor error

Frage 37

Frage
What is a common method used to control the speed of the AC propulsion motor on a diesel-electric propulsion ship?
Antworten
  • Change the input frequency of the voltage to the motor
  • Increase the motor voltage
  • Decrease the motor voltage

Frage 38

Frage
What keep the line losses in a distribution circuit at minimum?
Antworten
  • Use higher voltage and lower current
  • Increase the number of thermal relays in the circuit
  • Use higher current and lower voltage
  • Add rubber insulation conductors to the circuit

Frage 39

Frage
The Wheatstone bridge is a precision measuring instrument utilizing the principle of changes in ____.
Antworten
  • resistance
  • inductance
  • capacitance
  • amperage

Frage 40

Frage
In a compound-wound motor, where is a portion of the line current flows through?
Antworten
  • Shunt field coils
  • Inertia poles
  • Stator
  • Frame

Frage 41

Frage
How does the speed of a synchronous motor change?
Antworten
  • Changing the input frequency
  • Interchanging any tow of the three live leads
  • Changing the voltage of the system
  • Increasing the field excitation

Frage 42

Frage
Which of the following is the function of an automatic voltage regulators provided on main switchboards?
Antworten
  • It varies field excitation to the generators
  • It governs prime mover speed to control voltage
  • Protect the switchboard from high voltage
  • Regulate the AC load on the generator

Frage 43

Frage
What will happen if you reverse the DC current flow through an electrical coil?
Antworten
  • Its two-pole field will reverse
  • It will reduce the amount of flux produced
  • It will change its impedance
  • It will reduce the power consumed

Frage 44

Frage
Power transformers are rated in _____.
Antworten
  • kilovoltamperes
  • kilowatt-amps
  • ampere-turns
  • kilowatt-volts

Frage 45

Frage
When the voltage and the current developed in an AC circuit reach their peak values at the same time, the power factor is considered to be _____.
Antworten
  • unity
  • lagging
  • leading
  • infinity

Frage 46

Frage
When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is ___.
Antworten
  • maximum
  • lagging
  • leading
  • minimum

Frage 47

Frage
The operating torque of the disk or timer element in an AC reverse power relay is obtained from _____.
Antworten
  • electromagnets
  • line voltage
  • a separate battery source
  • the main bus

Frage 48

Frage
One important difference between wye-connected and delta-connected generators is that delta connections have ____.
Antworten
  • line voltage equal to the phase voltage
  • line voltages equal to the vector sum of the phase voltages
  • phase voltage 90º out of sync
  • line current equal to the phase current

Frage 49

Frage
The load sharing characteristics of two diesel alternators operating in parallel are directly related to the setting of their governors’_____.
Antworten
  • speed droop
  • Load limit
  • idle speed
  • speed limit

Frage 50

Frage
Why is the engine room watch officers should keep a constant check on the loads carried by electric motors?
Antworten
  • Exceeding nameplate value shortens useful life
  • Low loads necessitate frequent insulation cleaning
  • Residual magnetism may increase
  • Energy is wasted if full loading is not utilized

Frage 51

Frage
Which of the listed conditions could cause a recently overhauled DC motor to have excessively hot winding and sparking at the brushed?
Antworten
  • Reversed interpole polarity
  • Low series field current
  • High shunt field current
  • Excessive humidity

Frage 52

Frage
Which of the following starting system should be carried out after overhaul of a motor?
Antworten
  • No load
  • Low speed
  • High speed
  • Medium speed

Frage 53

Frage
What is the common source of field excitation for synchronous motors?
Antworten
  • DC rectifier
  • Low voltage battery
  • Motor attenuator set
  • AC supply

Frage 54

Frage
What is a component used to protect the DC generator circuits against malfunctions due to prime mover power loss?
Antworten
  • Reverse current relays
  • Main bus disconnect links
  • A separate battery back-up
  • Reverse power relays

Frage 55

Frage
Due to the operating characteristics of the system, time lag fuses (or dual-element fuses) are necessary for use in _______.
Antworten
  • motor starting circuit
  • main lighting circuits
  • emergency lighting circuits
  • general alarm circuits

Frage 56

Frage
Equalization of the power factors of two alternators operating in parallel is accomplishedin what manner?
Antworten
  • Accomplish automatically by the automatic voltage regulator
  • Manually adjusting the governor controls
  • Manually adjusting the output of current transformers
  • Accomplish automatically by the designed action of the governors

Frage 57

Frage
Which of the following electrical instrument is the safest to use in taking the current even without switching off or opening the circuit?
Antworten
  • Clamp meter
  • Meager tester
  • Ammeter
  • Multi tester

Frage 58

Frage
Relative to the secondary winding of a step-up transformer, the primary winding will have ____.
Antworten
  • fewer turns
  • more turns
  • same number of turns but smaller wires
  • twice as many turns

Frage 59

Frage
What will happen if connections on a DC shunt motor are changed on either the field connections, or the armature connections?
Antworten
  • Direction of rotation will be reversed
  • Motor will not run
  • Direction of rotation will be the same
  • Motor will run as a generator

Frage 60

Frage
What is the purpose of DC generator brushes?
Antworten
  • Conduct electric current to an outside current
  • Neutralize armature reaction
  • Convert DC current to AC current
  • Provide excitation to a DC generator

Frage 61

Frage
A switchboard for an AC electrical system requires the use of which of the following devices?
Antworten
  • Frequency meter
  • Ohmmeter
  • Induction voltage regulator
  • Current transformer governor

Frage 62

Frage
A bus disconnect link is used to isolate ___.
Antworten
  • the generator circuit breaker from the bus
  • one bus bar from the ground detection system
  • different bus phases form the equalizer connection
  • positive and negative buses from the neutral

Frage 63

Frage
The purpose of a magnetic relay is to ______.
Antworten
  • remotely open and close contacts
  • open a circuit only in the event of overload
  • provide overcurrent protection during starting
  • relay voltages at increased power

Frage 64

Frage
As storage battery for an emergency lighting and power system must have the capacity to ____.
Antworten
  • close all watertight doors twice
  • open all watertight doors four time.
  • open and close all watertight doors in six consecutive cycles within a 20 second period
  • none of the above

Frage 65

Frage
On an engine throttle control system, the auxiliary control circuits are provided with devices to prevent excessive over travel of the actuating valve by the control motor. What are these devices?
Antworten
  • Limit switches
  • Overlap sensors
  • Differential relays
  • Analog relays

Frage 66

Frage
The shunt of a DC ammeter should be connected in _____.
Antworten
  • series with the load and in parallel with the meter movement
  • parallel with the load in series with the meter movement
  • parallel with the load and in parallel with the meter movement
  • series with the load and in series with the meter movement

Frage 67

Frage
When a transformer is used to step-down voltage, the low voltage winding is ___.
Antworten
  • the secondary coil
  • part of the core
  • the primary coil
  • not insulated

Frage 68

Frage
What inidicates a violent gassing developed by a lead-acid battery during charging?
Antworten
  • Charging rate is excessive
  • Plate separators are grounded
  • Cell voltages are excessive
  • Specific gravity is insufficient

Frage 69

Frage
When the non-essential load has been removed from the feeder system but the service generator remains overloaded, what device automatically activates?
Antworten
  • Overcurrent tripping device
  • Preferential tripping system
  • Time delay trip device
  • ACB trip device

Frage 70

Frage
What is the function of capacitors which are commonly used on power supply circuits for engine room automation consoles?
Antworten
  • To filter out ripple for rectification
  • prevent overloads
  • act as a permanent load
  • decrease the average value of the output voltage

Frage 71

Frage
What do you call the device where a low input voltage is imparted to it which then delivers a high output voltage?
Antworten
  • Step-up transformer
  • Primary transformer
  • Secondary transformer
  • Step-down transformer

Frage 72

Frage
What electrical component intitiates the division of the reactive KVA load between paralleled AC generators?
Antworten
  • Voltage regulators
  • Prime mover governors
  • Proportioner
  • Phase balance relay

Frage 73

Frage
The circuit power factor of an AC generator operating singularly is determined by the ____.
Antworten
  • connected load
  • prime mover speed
  • ground current
  • generator’s rated voltage

Frage 74

Frage
What do you call a torque produced by a motor when the shaft will not turn, even though rated voltage is applied to the stator?
Antworten
  • Locked rotor torque
  • Pullout torques
  • Breakdown torque
  • Torque margin

Frage 75

Frage
What will happen if you reverse the DC current flow through an electrical coil?
Antworten
  • Reverse its two-pole field
  • Reduce the power consumed
  • Change its impedance
  • Reduce the amount of flux produced

Frage 76

Frage
Which of the following provides the initial torque to turn a DC generator?
Antworten
  • A mechanical prime mover
  • Residual magnetism in the armature
  • Residual magnetism in the field poles
  • Residual magnetism in voltage regulator

Frage 77

Frage
The division of kilowatt load between two AC generators operating in parallel is controlled by the settings and characteristics of the ____.
Antworten
  • prime mover governors
  • reverse power relays
  • field rheostat
  • voltage regulators

Frage 78

Frage
On some diesel-electric ships, the DC propulsion motor will only attain half speed when the generator fields are fully excited. How should the speed above this be obtained?
Antworten
  • Raise the generator engine speed
  • Rotate brush alignment
  • Decrease excitation
  • Lower the generator engine speed

Frage 79

Frage
What do you call a DC generator used to supply direct current in order to maintain an AC generator field?
Antworten
  • Exciter
  • Rotor
  • Stator
  • Armature

Frage 80

Frage
Transformer cores are laminated to reduce ____.
Antworten
  • eddy currents
  • secondary flux
  • leakage flux
  • tertiary flux

Frage 81

Frage
To test the feeder system for grounding, the three earth lamps will be activated when this switch is manipulated.
Antworten
  • The push button switch
  • Selector switch
  • Micro switch
  • Lamp switch

Frage 82

Frage
A transformer works on the basic principle of ____.
Antworten
  • mutual induction
  • self impedance
  • attraction and repulsion
  • increasing power

Frage 83

Frage
What is the simplest method of controlling the terminal voltage of compound-wound DC generator?
Antworten
  • With a hand-operated field rheostat connected in series with line shunt field circuit
  • Separate exciter in a series with the shunt field
  • Carbon pile regulator in series with load
  • Balance coil diverting neutral current through the shunt field

Frage 84

Frage
Which of the following types of motor has two separate field windings usually connected in parallel with the armature circuit?
Antworten
  • Compound-wound motor
  • Series-wound motor
  • Shunt-wound motor
  • Induction motor

Frage 85

Frage
Which of the following types of motor whose speed at normal operation is constant or practically constant?
Antworten
  • Universal motor
  • Series-wound motor
  • Synchronous speed motor
  • Regulated speed motor

Frage 86

Frage
A circuit with a blown fuse would be described as ____ _____
Antworten
  • open circuit
  • short circuit
  • bonded circuit
  • grounded circuit

Frage 87

Frage
How would you describe a circuit with a blown fuse?
Antworten
  • Open circuit
  • Short circuit
  • Bonded circuit
  • Grounded circuit

Frage 88

Frage
Which of the following operating characteristics for DC motors is considered to give high starting torque?
Antworten
  • Series
  • Shunt
  • Cumulative-compound
  • Differential-compound

Frage 89

Frage
The resistance value of a resistor in a circuit can best be determined by the ______.
Antworten
  • band markings on the resistor
  • single solid body color of the resistor
  • amperage value written on the resistor
  • physical size of the resistor

Frage 90

Frage
What is the recommended practice on the frequency of the incoming machine prior to closing the breaker when paralleling two AC generators?
Antworten
  • Slightly greater than the line frequency
  • Slightly less than the line frequency
  • The same as the line frequency
  • Greater than the line frequency

Frage 91

Frage
When two AC generators are being paralleled, the breaker should be closed with the synchroscope pointer rotating in what direction?
Antworten
  • FAST direction, just before the 12 o’clock position
  • SLOW direction, just before the 12 o’clock position
  • FAST direction, just after the 12 o’clock position
  • SLOW direction, just after the 12 o’clock position

Frage 92

Frage
What is the characteristic of the mica used in the commutators of DC machinery?
Antworten
  • Harder than copper
  • Softer than copper
  • Same hardness as copper
  • Softer than copper but wears away at slower rate

Frage 93

Frage
Regarding an induction motor, where is the output power developed related to?
Antworten
  • Slip of the rotor
  • Speed of the rotating field
  • DC filed excitation
  • Current flow in the interpoles

Frage 94

Frage
What type of AC single-phase motor will also operate on direct current?
Antworten
  • Series-wound
  • split-phase
  • Shaded-pole
  • Repulsion-start

Frage 95

Frage
What do you call an AC motor which uses rheostat in the motor circuit to vary the speed?
Antworten
  • Wound rotor induction motor
  • Squirrel cage induction motor
  • Regenerative braking motor
  • Squirrel-cage induction motor

Frage 96

Frage
Which of the following is the most common of excitation for synchronous motor?
Antworten
  • DC supply
  • Step-up transformer
  • AC supply
  • Poor contact of brushes

Frage 97

Frage
Which of the listed transformers uses a single winding to produce voltage transformation?
Antworten
  • Autotransformers
  • Step up transformers
  • Stepdown transformers
  • Isolation transformers

Frage 98

Frage
What type of electric motor is commonly used to start small auxiliary diesel engines?
Antworten
  • Series
  • Synchronous
  • Cage
  • Shunt

Frage 99

Frage
Which of the following electric motors would be the most reliable to use on the open main deck of a vessel?
Antworten
  • Watertight motors
  • Synchronous motors
  • Drip proof motors
  • Squirrel cage motors

Frage 100

Frage
When a megohmmeter is used to test the dielectric strength of wire insulation, what causes the intial dip of the pointer toward zero?
Antworten
  • The capacitance of the circuit
  • The dielectric absorption effect of the insulation
  • The leakage of current along the surface of dirty insulation
  • Good insulation

Frage 101

Frage
On a modern 13 amp square pin electric plugs, which of the following statements is true ?
Antworten
  • The fuse is at the neutral connection.
  • The neutral wire is coloured brown.
  • The live wire is coloured blue.
  • The earth wire goes to the centre top connection.

Frage 102

Frage
The timer element of a reverse power relay will activate when ___
Antworten
  • the power flow is the same as the tripping direction
  • the power flow is the opposite to the tripping direction
  • the movement if the disk is damped by a permanent magnet
  • the load difference generators is more than 10 percent

Frage 103

Frage
The difference between the synchronous speed of a three phase induction motor and its operating speed is called slip and may be correctly expressed as_______.
Antworten
  • a percent of synchronous speed
  • the reduced amp rating
  • the decrease in shaft torque
  • reduced fuel consumption

Frage 104

Frage
What determines the cycle per second developed by the alternator aboard your vessel?
Antworten
  • The speed of the engine driving the alternator
  • The resistance applied to the field rheostat
  • The synchronous speed of induction
  • The adjustment made to the voltage regulator

Frage 105

Frage
Which of the following statements identifies the difference between the primary windings and the secondary windings of a 2:1 step down transformer?
Antworten
  • The secondary windings have half as many turns as the primary windings
  • The secondary windings have twice as much resistance as the primary windings
  • The secondary windings use smaller wires than the primary windings
  • The secondary windings can only provide half as much current as the primary windings

Frage 106

Frage
What will happen if there is a change in field excitation of an alternator operating in parallel?
Antworten
  • There will be a change in voltage output
  • There will be change in alternator frequency
  • There will be a change in kilowatt load
  • There will be a change in current rating

Frage 107

Frage
What is the advantage of DC motors over AC motors?
Antworten
  • Offer infinite speed variations
  • They are less expensive
  • They require less maintenance
  • They offer slow speed

Frage 108

Frage
A galvanometer is an instrument used to measure ____.
Antworten
  • very small amounts of current or voltage
  • thickness of galvanized metal
  • resistance of electrical wiring insulation
  • quantity of galvans in an electric circuit

Frage 109

Frage
Regulations require emergency diesel engine starting systems to have sufficient capacity to provide power for at least ____.
Antworten
  • six consecutive cranking cycles
  • three continuous starting sequences
  • nine repeated starts under load
  • twelve cranking periods of 5 seconds

Frage 110

Frage
In a three-phase, open-delta connected transformer, the line current is equal to ____.
Antworten
  • the phase current
  • three times the phase current
  • the sum of any two phase currents
  • the difference of any two phase currents

Frage 111

Frage
In a running electric motor, why are we using a sound listening bar?
Antworten
  • To detect fault in ball bearing
  • To detect fault in motor windings
  • To detect fault in stator windings
  • To detect if motor is overload

Frage 112

Frage
Why is an armature cores in a DC generator made of laminated steel sheets?
Antworten
  • To reduce eddy current losses
  • To fit the curvature of the frame
  • To increase the hysteresis effect
  • To allow for easy assembly

Frage 113

Frage
What will be the next step after closing the circuit breaker to place two similar alternators in parallel?
Antworten
  • To balance the kilowatt load
  • To maintain the power factor
  • To reduce voltage load
  • To balance ampere load

Frage 114

Frage
What is the reason why one of the generator or motor bearings generally insulated from the end housing?
Antworten
  • To preventcirculation of shaft currents induced in the machine’s frame
  • To prevent excessive field winding heat
  • To remove current leakage from the shaft
  • To minimize rapid brush wear

Frage 115

Frage
Why is a modern DC generators fitted with commutating poles?
Antworten
  • To reduce sparking
  • To prevent motorizing
  • Reduce spring pressures ion the brushes
  • Reduce the load on the main poles

Frage 116

Frage
Why is there an amortisseur windings installed in a synchronous motor?
Antworten
  • To dampen any speed fluctuation as a result of load change
  • To produce a higher power factor
  • produce a higher power factor
  • eliminate arcing between the stator and the rotor

Frage 117

Frage
What is the function of the interpoles installed in DC motors?
Antworten
  • To limit the production of counter electromotive force
  • To provide greater torque by strengthening the main field
  • To limit the starting surge current

Frage 118

Frage
What is the purpose of squirrel-cage windings in a synchronous motor?
Antworten
  • To provide a means for starting
  • To provide more precise balancing
  • To produce a higher power factor
  • To eliminate arcing between the stator and the frame

Frage 119

Frage
When energizing a DC propulsion motor using Local override manual control, What should the variable resistor do?
Antworten
  • Turn to a position which initializes motor rotation and then turn back to the slow position
  • Turn all the way to the full run position then quickly back toslow
  • quickly to the mid position
  • quickly to the full run position

Frage 120

Frage
What is an operating characteristic appearing on the name plates of shipboard AC motors?
Antworten
  • Temperature rise
  • type of overload protection
  • rated slip
  • locked rotor torque

Frage 121

Frage
When mixing electrolyte, which if the following precautions should always be observed?
Antworten
  • Add the acid to the water
  • Use a heavy duty aluminum pail
  • Add the water to the acid
  • Mix the solution outdoors

Frage 122

Frage
If the approximate voltage to be measured in an electric circuit is not known, you should _____.
Antworten
  • use the highest voltage range on the voltmeter
  • Use the lowest voltage range on the voltmeter
  • connect the meter in series with the circuit
  • only have to calibrate the meter before using it

Frage 123

Frage
The basic operating principle of a transformer is attributed to ___.
Antworten
  • electromagnetic induction
  • variance of a conductor in a magnetic fluid
  • mutual reaction
  • thermionic emission

Frage 124

Frage
How is kilowatt load divided between two AC generators operating in parallel?
Antworten
  • Adjusting the governor controls
  • Varying the excitation voltage
  • Increasing both prime mover speeds simultaneously
  • Decreasing both prime mover speeds simultaneously

Frage 125

Frage
An increase in which of the listed conditions will increase the speed of synchronous electric motor?
Antworten
  • Frequency
  • Voltage
  • Armature current
  • Inductance

Frage 126

Frage
Which of the following meters uses a shunt connected in series with the load, but parallel with the meter movement?
Antworten
  • ammeter
  • voltmeter
  • power factor meter
  • wattmeter

Frage 127

Frage
How is the capacity of a storage battery being measured?
Antworten
  • Ampere-hours
  • Volts
  • Volt-hours

Frage 128

Frage
A general purpose electrical multimeter can be used to directly measure ____.
Antworten
  • current
  • watts
  • field flux
  • all of the above

Frage 129

Frage
What is the simplest method of controlling the terminal voltage of compound-wound DC generator?
Antworten
  • With a hand-operated field rheostat connected in series with the shunt field circuit
  • With a separate exciter in series with the shunt field  
  • With a balance coil diverting neutral current through the shunt field
  • With a carbon pile regulator in series with the load

Frage 130

Frage
A ‘dead front’ switchboard is one ____.
Antworten
  • with insulated switches and no exposed terminals
  • without switches on it
  • without circuit breakers
  • without safety hand rail nor rubber mats

Frage 131

Frage
When the feeder system has no ground fault, what does the pointer of the insulation resistance indicates
Antworten
  • Infinity ohm resistance
  • Zero ohm resistance
  • 500 ohm resistance
  • 100 ohm resistance
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