competence 7

99問 • 2ヶ月前

問題一覧

Moisture accumulating in electric motors and generatos windings having a cold insulation resistance greater than 50,000 ohms may be baked out with internal heat. This heat can be developed by

feeding current into the windings at low voltage

What precaution should be taken with a vessel's impressed current cathodic protection system after a drydocking period during which the hull has been painted?

The unit should remain off for the specified amount of time so as not to disturb curing

The schematic symbol for an operational amplifier in an analogue circuit is a

Triangle

A three-phase squirrel-cage induction motor will run hot due to

Open stator coils

A capacitor can be tested using a megohmmeter or an ohmmeter, if the meter is connected to a shorted capacitor, the meter pointer should

immediately deflect to and remain at zero

A switchboard for an AC electrical system requires the use of which of the following devices?

Frequency meter

When changing tubular fuses always use a

Fuse puller

The greatest single cause of electrical failure is

The breakdown of insulation

What will you do if the generator is exposed to rain or any water?

Make a megger test

A safety device in an electrical circuit consisting of metal strip that melts when the current exceeds the safe level is called

fuse

An electric tachometer receives the engines speed signal from?

bimetallic sensing device

A current at which a magnetic-type overload relay tends to trip maybe decreased by raising the plunger further into the magnetic circuit of the relay. This action will

Increase magnetic pull on the plunger and requires less current to trip the relay.

What does teh variable resistance placed in the rotor circuit of a wound-rotor induction motor provide?

speed control

Periodic testing of circuit breaker is necessary to assure that a correct rated and properly installed unit

will continue to provide the original degree of protection

Which of the following materials is recommended for finishing the slip rings afeter grinding or turning?

crocus cloth

What kind of device that has two pieces metal joined together so that when its junction is heated, a voltage is produced?

Thermocouple

When removing ball or roller bearings from the shaft of a motor, you should use a

wheel puller

What do you call on a periodic testing by a shore side support technician using a special camera which can detect potentially dangerous loose or corroded bus bar and controller

heat sensitive thermography

When the equivalent circuit diagram of double squirrel-cage induction motor is constructed the wo cages can be considered

in parallel

What motor is fitted with an instantaneous overload relay?

Winch

If both the "high level and low level" alarms come on for the same address of a centralized control console, the most likely problem is alan

sensor failure

Which of the listed procedures should be carried out to prevent moisture damage to electrical apparatus during extended periods of idleness?

Place heat lamps in the motor housings

A common type of protective covering used on electrical conductos is

fibrous braid

When a nickel-cadmium bateery begins gassing while connected to the battery charging circuit, you should

do nothing as this is a normal condition when charging

A molded-case breaker provides protection against short circuits by using?

electromagnet

What may happen to the components of a winch master control switch, if the cover gasket becomes deteriorated?

Rapid corrosion of switch components

What should you use to determine if a stator coil is grounded?

megger

The charging of lead-acid storage batteries will always result in ?

a dangerously explosive gas being liberated

With both ends of a three conductor cable disconnected and arranged without the conductors touching each other, an ohmmeter reading of'zero' ohms between the ends of one conductor would indicate

continuity

What is a device that changes an input signal of one type into an output signal of a different type that is proportional to the original input?

transducer

What gives the information about the speed of a motor in D.C. Generator ?

Speedometer

To check the three line fuses of three-phase system consisting of a three-phase motor, you must

make sure the motor is operating at full load to guard against a false reading

Periodic testing of circuit breakers is necessary to assure that a correct rated and properly installed unit

will continue to provide the original degree of protection

How should controller contacts be routinely cleaned?

wiping with a clean dry cloth

Which of the following safest precautionary measure is to be done prior working on the motor of the cargo winch?

Switch off main switch and put sign do not switch on

Four lamps are connected in parallel in a single circuit, If one of the lamp burns out, the other will

burn with their original intensities

Electrical leads and insulation on a motor should be painted with

insulating varnish

Which of the following physical characteristics does a wound-rotor induction motor possess that a squirrel-cage motor does not?

Slip rings

Why should you use a high impedance multimeter when troubleshooting electronic equipment?

so as not to load down the circuit and obtain erroneous voltage readings

Air gap readings should be periodically taken for electrical generation equipment. The best tool to use to take these measurement is a

tapered, long blade gage

Which test on a transformer provides information about the regulationm, efficiency and heating under load condition?

Back to back test

It is a type of electrical fault that happens when a phase conductor is completely or partially interrupted:

Open circuit fault

The windings of electric generators during short idle periods should be

kept warm by using strip or space heaters

The part of teh shipboard electrical system used to control the distribution of power to the branch circuits, is the

main switchboard

A temperature instrumentation system for an engine room consoel consistes of resistance temperature detector(RTD), a measuring bridge circuit, and a meter( or alarm circuit).Which of the following statements is true concerning the measuring bridge circuit?

The resistance bridge is said to be balanced when its output voltage is zero

In the event of a powr failure during cargo loading operations, which of the following can stop the movement of an electric powered cargo winch?

A spring set brake

A device which can be used to check the calibration of a circuit breaker is a

portable low voltage high current testing unit

Before reassembling any machinery, what should you do?

apply a heavy coat of oil to all mating surfaces

Air gap readings should be periodically taken for electrical generation equipment. The best tool to use to take these measurements is a

tapered, long blade gage

A semiconductor that decreases in resistance with an increase in temperature is known as ?

Thermistor

What should be done to protect the rotor of a motor disassembled for maintenance or overhaul?

it must be supported by two "V" notched blocks

What is variable-resistance component as a control device in electrical circuit ?

Potentiometer

What kind of electrical cable that is widely used and is highly resistant to mechanical damage?

aluminum cable covered with insulation

When trouble shooting electronic equipment, what is the first step to be taken before testing the circuit voltage?

check the voltage supply from the power source

The purpose of a main switchboard circuit breakers reverse-power trip is to

prevent alternator motorization

Temporary repairs to an open DC propulsion armature coil can be made by

disconnecting coil ends, insulating each, and short circuiting the two commutator bars

When charging lead-acid batteries, you should reduce the charging rate as the battery nears its full charge capacity to

prevent excessive gassing and overheating

When shipboard electrical distribution circuits are connected in parallel, additional parallel circuits will cause the total circuit resistance to

decrease, causing an increase in the line current

What is a device that converts fluid powers into linear mechanical force and motion that consists of a movable piston, connecting rod, and plunger operating in a cylindrical cavity?

Cylinder

During maintenance of circuit breakers,

inspect for wear and misalignment of main contacts

What is used in most for starting three-phase induction motors of five (5) horsepower or less?

across the line starters

Periodic testing of circuit breakers is necessary to assure that a correct rated and properly installed unit

will continue to provide the original degree of protection

You are testing the insulation in an AC generator with a megohmeter. the resistance value of a dry, clean winding will

continue to rise the test potential is maintained, becoming fairly steady as the leakage current stabilizes

Which of the following data is required to draw the circle diagram for an induction motor ?

Block rotor test, no load test and stator resistance test

The removal of paint from electrical equipment such as generators, should be cautiously undertaken because

the paint dust is composed of abrasive and semi-conducting materials which impair insulation

A reversible electric motro with worm gear that is connected to the flywheel to postion engine parts is the

turning gear

If a small electric motor is immersed in salt water it should be I. washed in fresh water II. dried in an oven III. blow air until it dries

I only

To carry out an insulation resistance test, one terminal of the megohmmeter should be connected to the winding, with the other terminal being connected to the

frame of the machine

Before working on an electric motor starter panel located on the main deck, what should you do FIRST?

Open the circuit breaker and tag out

A fuse the blows often should be replaced only with a fuse of

the recommended current and votlage rating

Electrical Insulating rubber gloves should be dielectrically tested every how many months?

6 months

it is a type of temperature sensor that has the characteristic of being very accurate, linear and has a good long term stability

RTD's

A self-excited DC generator fails to come up its normal 440 volts. What could be the probable cause?

low armature speed

A common type of protective covering used on electrical conductors is,

Fibrous braid

The air gap provided in induction motors should be checked periodically with a feeler gage to detect an unequal air gap and

mechanical damage to rotor

A temperature instrumentation system for an accomodation reefer room consists of a resistance temperature detector (RTD), a measuring bridge circuit and a meter or alarm circuit. Which of the following is true concering the measuring bridge circuit?

The resistance bridge is said to be balanced when its output voltage is zero

Electrically operated safety devices on auxiliary diesel engines functions to stop the engine by

shutting off fuel supply

A molded-case circuit breaker provides protection against short circuits by using alan?

electromagnet

The proper way to apply plastic electrical tape to an electric cable splice to

wind the tape so that each turn overlaps the turn before it

The division of kilowatt load between two paralleled alternators is determined by the ?

load-speed characteristics of the governors

What is the result if the solenoid coil burns on a cargo winch with an electrical brake?

The brake will be set by spring force

The air gap provided an induction motor should be checked periodically with a feeler gage to detect

any increase in rotor bearing wear

Encrusted dirt accumulated inside a motor should be removed with a

Fiber scraper

A temperature instrumentation system to an engine room console consists of a resistance temperature detector (RTD), a measuring bridge circuit, and a meter (or alarm circuit) which of the following statements is true concerning the measuring bridge circuit?

The resistance bridge is said to be balanced when its output voltage is zero

When replacing a fuse with one of a higher rating than the original, which of the following is true?

it endagners the apparatus it is supposed to protect

The purpose of a motor under voltage protection device is to

prevent high armature current when power is restored

The power sclae of circle diagram of an induction motor can be fouond from

short-circuit test only

What electrical apparatus can test insulating efficiency in an electric installation?

Megger tester

When reading electrical motor controller diagrams, it helps to know that

current paths in the power circuit are drawn as heavy lines and in control circuit as lighter lines

What devices is fitted to prevent the generator windings from absorbing moisture while at stanstill?

Space heater

Any electric motor can be constructed to be?

explosion proof

A common type of protective covering used on electrical conductos is

rubber or plastic

Which of the following statements concerning the maintenance of solid-silver Contacts in relay and auxiliary control circuits is correct?

They should be filed with a fine-cut file when projection extend beyond the contact surface

What can you do if the generator is exposed to rain or any water?

Make a megger test

What is the cause when an alternator failed to produce line voltage?

exciter generator failure

Moisture as a result of condensation occurring inside of the cargo winch master switches, can be reduced by?

using strip heaters inside the switch box

Regulations require each motor controller to have a wiring diagram located

on the inside of the controller door

A device which can be used to check the calibration of a circuit breaker is a

portable low voltage high current testing unit

Which of the following statements concerning analog and digital devices are correct?

The variables in digital systems are fixed quantities and the variables in analog systems are continuous quantities

Competence 1

Emm · 112問 · 2ヶ月前

Competence 1