MEO Class 4 - Electrical Test 5

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Which of the following are benefits of modifying ward Leonard control system by replacing motor set with a thyristor speed controller

Reduces the overall cost

Increases operating speed range of system

Reduces system maintenance

Reduces overall space required

Enhanced speed regulation by making the motor acceleration uniform

Increases efficiency of system especially lightly loaded

Which statement is true for reactor starter for electrical motor

In reactor starter, a Coil with iron core is connected in parallel with motor during starting

Minimal reduction in starting torque available

Starting current is limited in proportion to voltage

Advantage of this method is its low cost in comparison to other starters

Which trip is present in emergency generator?

Under voltage trip

Over speed trip

None

Over voltage trip

An amplifier is said to suffer distortion when its output is

Low

Noisy

Larger than is input

Different from input

Reversing any two of the three rotor leads on induction motor will _____________.

decrease motor performance

reverse the motor

increase motor performance

have no effect on the direction of rotation or motor performance

Motor having rheostat in motor circuit to vary speed in cell

Squirrel cage motor

Regenerating breaker motor

Wound round induction motor

Synchronous motor

To repair a small electric motor which was submerged in saltwater, you should

Rinse all electrical parts with a carbon tetrachloride cleaning solvents and then blow dry the motor with compressed air

Wash it with f.w and apply an external source of heat.

Send to ashore to an approved service facility

Renew the windings

Large cable sizes are formed as individual conductors that may be comprised of several smaller strands to

reduce the overall weight of the wire run

reduce the number of supports needed for a horizontal overhead run

all of the above

obtain the flexibility required for easy handling

An operating characteristic appearing on the name plates of shipboard AC motor is ___________

Temp rise

Locked rotor torque

Type of windings

Input kw

Which statements are true of starts used for electric motor. Mcq

Rheostat starting can be used with slip ring motors

Soft stator is made of semiconductor

Advantage of Reactor start is their relatively low cost

Frequency convertor cannot be used as stator

NER- what is true for high voltage circuit?

To limit max load current

Main switchboard earthed

Not known

Neutral earth resonance

Which of the following are TRUE with regards to incorrect synchronization of Alternators?

If voltages are not in phase and circuit breaker is closed, the phase difference will cause low current to flow from alternator and alternator will run on low load

If incoming supply voltage is lesser than that of bus bar, the alternator will start drawing power from bus bar and start motoring

If incoming supply voltage is higher than that of bus bar, the alternator will start drawing power from bus bar and start motoring.

If frequencies of bus bar and alternator don???t match, alternator will run on low frequency on synchronization.

If voltages are not in phase and circuit breaker is closed, the phase difference will cause overloading and potential black out.

If frequencies of bus bar and alternator don???t match, alternator will run on high frequency on synchronization.

Arrange the following in correct sequence foe achieving correct KW sharing when an AC generator is paralleled with live bus bar and generator has some owe factor as others in system 1. Synchronize the incoming generator in terms of voltage, frequency and phase. 2. Trim voltage of the machine which has/ have lower load current to increase excitation 3. Increase speed on incoming machine while lowering than that of others connected to system 4. Adjust machine voltage to keep overall system efficiency ready. 5. Adjust the governor control switch on main switch board to increase the fuel to its prime mover

Adbc

Aebc

Aecb

Aec

Acbd

Adc

In common collector transistor collector amplifier voltage gain

Always constant

Depends on output impedance

Depends on output signal

Cannot exceed unity

Which statement is true for any storage battery

Amp hr. efficiency of alkaline battery is high than lead acid battery

Alkaline battery can left in any state of charge or discharge

All

Watt hr. efficiency of alkaline is more than lead acid battery

The depletion region in semiconductor diode is due to

Crystal doping

Forward biasing

Reverse biasing

Migration of mobile charge carriers

For leading power circuits which of the following can be used?

Neither shunt capacitors nor shunt reactors

Either shunt capacitors or shunt reactors

Shunt capacitors only

Shunt reactors only

Motor having rheostat in motor circuit to vary speed in cell

Squirrel cage motor

Synchronous motor

Regenerating breaker motor

Wound round induction motor

Electric motor stator- true statements? (mcq)

Freq. convertor can be used as starter

Generator used only with slip rings motors

Not known

Auto transformer act as rheostat starter

Which of the following is not self-starting motor?

Squirrel cage motor

Synchronous motor

Induction motor

Split phase motor

Which of the following are true for Thermistors (mcq)

Thermistors are semiconductors devices

In a Positive temperature coefficient (PTC) thermistors, resistance increases with temperature increase

NTC thermistors are generally used for monitoring coolant and engine lube oil temp in automobiles.

PTC thermistors can be used as resistance thermometers in low temperature environments.

–ve temperature coefficient (NTC) thermistors, can be used as replacement of fuse.

Current applied to lead acid battery would lead to

Higher thermal voltage

Decrease in specific gravity of electrolyte

Increase generation of H2 gas

Lower terminal voltage high charging

Which of the following are true for shipboard storage batteries?

Emgy batteries should never be stored in battery room

The deck below the cells should be protected with acid resisting or alkaline resisting materials

Construction should be so as to prevent emission of spray

Battery banks above 2 kw should be kept in battery room only

If voltage is above 200v insulation stands must be used

Common emitter amplifier is characterized by

Very high output impedance

Signal phase reversal

Moderate power gain

Low voltage gain

Motor overhaul is to be done which statements are true?

Stator should be isolated

Not known

Tag on overall ship

To prevent the race of DC series, motor what arrangement should make?

Use a strong series weak shunt compound DC motor

All

Use a weak series strong shunt compound DC motor

Always start at heavy load

Which of the following statements represents an application of a silicon controlled rectifier?

To provide DC power for a main propulsion motor

For sensing flame in an automated burner.

For use as a voltage reference diode

To eliminate power supply hum.

Which of the following are TRUE with regards to a Synchro scope? (MCQ)

One of the coils in the armature is fed through a Capacitor while the other is fed through an Inductor

The field produced by the coils rotates the magnetic armature pointer at a speed relative to the voltage of the bus-bar supply.

One of the coils in the armature is fed through an Inductor while the other is fed through a Resistor.

The coils produce a two-phase rotating field.

The rotating armature has two coil windings parallel to each other.

Which of the following method used for biasing a BJT in integrated circuits is considered independent of transistor beta?

Fixed biasing

Voltage divider bias

Collector feedback bias

Base bias with collector feedback

Mercury filled thermometer should never be used to determine the temp of the battery electrolyte bcoz accidental breakage of thermometer can cause

Severe sparking and explosions

Corrosion of battery terminals

Contamination of the electrolyte

Rapid oxidation of battery plates

Voltage generator by most AC generators is fed from the machine to the bus by means of

Direct connection from stator

Brushes on slip rings

Brushes on commutator

Slip rings on commutator

which of the following is true for synchroscope (mcq)

the rotating armature has two coils windings perpendicular to each other.

The coils produce a single phase rotating field

the coil produces a three phase rotating field

The field produces by the coils rotates the magnetic armature pointer at a speed relative to the frequency of the bus bar supply

one of the coil in the armature is fed through a capacitor while other is through resistance

Which of the following are true about a temp measuring ckt employed in in a data logger system? 1. A Wheatstone bridge can be used in conjunction with a Wheatstone bridge induction thermometer 2. Thermometer is energized using a constant current source and voltage developed is measured in potentiometer type method 3. Inductance of thermometer will change with change in temp

2 & 3 only

1 only

1 & 2 only

1 & 3 only

2 only

Which of the following will prevent a DC generator from becoming motorized?

Motorization trip

Reverse current relay

Overcurrent relay

Reverse power relay

What happens when battery is excess charged?

Don’t remember

Gassing increases

Electrolyte decreases

For t/c, leak current in P-N diode is produced by?

Not known

Heat energy

Chemical energy

Barrier potential

Which of the following is not true about star delta starters

Can only be used with induction motor delta connected in supply voltage

Typically used to start the motor with lower voltage

Popular bcoz relatively inexpensive

Gives lower starting current than DOL

Disadvantage of ward Leonard system (mcq)

System operates in very narrow speed range

expensive

Speed regulation is difficult to achieve as motor acceleration is uniform

Requires high maintenance

Overall efficiency of the system is low especially when lightly loaded

Motor generator set requires lot of space

Which of the following does not change in a transformer?

Current

Voltage

Frequency

Fuses replaced in series with thermal trip type ckt breakers are used for?

Short ckt protection

Sustained overload protection

Short duration surge protection

Time delay protection

An amplifier is said to suffer from distortion when its output is

Larger than is input

Noisy

Low

Different from input

Squirrel cage used in synchronous motor for?

Not known

Just for starting

Uniform balancing

Improving p.f

Which of the following are TRUE with regards to incorrect synchronization of Alternators?

If frequencies of bus bar and alternator don???t match, alternator will run on high frequency on synchronization

If voltages are not in phase and circuit breaker is closed, the phase difference will cause overloading and potential black out

If incoming supply voltage is higher than that of bus bar, the alternator will start drawing power from bus bar and start motoring

If frequencies of bus bar and alternator don???t match, alternator will run on low frequency on synchronization.

If voltages are not in phase and circuit breaker is closed, the phase difference will cause low current to flow from alternator and alternator will run on low load

If incoming supply voltage is lesser than that of bus bar, the alternator will start drawing power from bus bar and start motoring.

In capacitor, energy stored is? SURE

Electrostatic energy

Potential energy

Not known

Kinetic

Across the line starters are used with AC motors to provide

Regulated starting current

High starting torque

Controlled starting acceleration

Reduced starting current

The main use of a Class-C amplifier is

as stereo amplifier

as distortion generator

as an RF amplifier

in communication sound equipment

Which statement is true for any storage battery

Amp hr. efficiency of alkaline battery is high than lead acid battery

All

Alkaline battery can left in any state of charge or discharge

Watt hr. efficiency of alkaline is more than lead acid battery

Which statement is true about any soft starters used in electrical motor

Soft starters progressively increase motor voltage with causing torque or current peak

Used to control the stopping of motor

Use of soft starters initially result in lower motor torque

Soft starters are based on semiconductors

In an earth neutral system, an earth fault will occur only

2 fault in two line

1 fault in 1 line

Don’t know

Two fault in 1 line

Max full wave rectifier efficiency possible by two diodes from a sinusoidal wave is (Half wave is 40.6%)

80.2

None of the above

82.1

81.2

Time is Up!

Time's up

MEO Class 4 – Electrical Test 5

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