Marine Electrotechnology. Test 5

Before taking insulation resistance readings of generator windings the automatic voltage regulators should be isolated and all semiconductor short circuited or disconnected in order to:

Prevent damage to sensitive electronic components from high voltage tester
Protect insulation resistance tester from being damaged
Prevent operation of automatic voltage regulator during insulation testing
Prevent charging of capacitive components within the automatic voltage regulator causing false regulation when generator restarts

A star connected induction motor operates on 220 V with power factor 0.7 and efficiency of 82 %. Its output is 8 HP. What is the phase, current and voltage?

I phase is 12.8 Ampere , phase voltage is 220 Volt.
I phase is 27.3 Ampere, phase voltage is 127 Volt.
I phase is 22.7 Ampere, phase voltage is 127 Volt.
I phase is 15.8 Ampere, phase voltage is 220 Volt.

How is the set pressure (opening pressure) adjusted on the cylinder head safety valve of a diesel engine?

By adjusting the spring pressure.
By adjusting the lift height of the spindle.
By adjusting the distance of the valve cone.
By fitting distance washers.

The potential of this thermocouple bridge is zero if all connections are kept at the same temperature. Why is the indication of the potentiometer zero ?

Because of the second balancing couple B.
Because the connections in A and B and in C and D are opposed
Because of the copper (Cu) calibration wiring connected to C and D.
Because A and B couples are opposed.

Indicate the correct characteristic of the amplifier 'A'.

A frequency range less than 1kHz
An output impedance greater than 10,000 Ohm
An input impedance lower than 1,000 Ohm
A voltage gain greater than 100,000

The power requirements for the excitation winding/circuit for a 3-phase alternator operating at rated output power are supplied by:

Independent power supply and rectifier unit
Independent battery supply
The main switchboard via a three phase rectifier
The alternators output itself via the automatic voltage regulator

Item No 2 of this Wheatstone Bridge is _____

the field wire fed by amplifier A
the thermal resistance fed by the output of amplifier A
the field balance indicating field wire of amplifier output
the feed-back coil fed by amplifier A

Generator 1 and 2 are working in parallel. Prime-mover 2 suffers a total fuel loss. The likely outcome is:

Generatorset 2 trips on reverse speed
No.2 generator trips on reverse power
No.1 machine overloads and trips out on overspeed
No.1 machine overspeeds and trips out on overload

Review Answers

Marine Electrotechnology. Test 5

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