FUNCTION -5 (ELECTRICAL)

181. Power factor is
     1. true power divided by the product of amperes and volts
     2. true power divided by apparent power
     3. KW divided by KVa
     4. all of the above

ANS.: D

182. After main power is restored, a timed sequential restart of motor-driven auxiliaries is necessary to avoid:
     1. Generator overload due to many motors starting at simultaneously
     2. Overloading creating earth faults
     3. Overvoltage due to current surges
     4. Over-frequency due to overspeed of generator

ANS.: A

183. A 3-phase induction motor is rated at 200 Amperes. Its initial direct- on-line starting current will be approximately:
     1. 100A
     2. 200A
     3. 50A
     4. 1000A

ANS.: D

184. An earth fault exists on the blue line of a 100 A bilge pump circuit. A second earth fault occurs on the yellow line of a 10 A ventilation fan circuit. The likely outcome is that:
     1. An open circuit occurs between earth fault and both motors trip out
     2. Both motors trip out on overload
     3. A short circuit occurs between earth faults and the ventilation fan fuse blows
     4. A short circuit occurs between earth fault and the bilge pump fuse blows

ANS.: C

185. The insulation resistance (IR) to earth of a new galley hot-plate is measured to be 30 Mohm. When three identical hot-plates are tested together their combined IR will be:
     1. 90 M ohm
     2. 30 M ohm
     3. 10 M ohm
     4. 6 M ohm

ANS.: C

186. A motor is protected by a thermal overcurrent relay. After tripping on overload it will not be possible to reset the overcurrent relay because the:
     1. Bimetallic strips need time to cool down
     2. Starter isolator automatically applies an interlock
     3. Oil dash-pot has also to be reset.
     4. Line contactor spring also has to be reset

ANS.: A

187. A 3-phase A.C. induction motor is running normally at its rated current of 150 A when a single phasing fault (open circuit) occurs in one line. The likely outcome will be:
     1. Line currents: 0 A, 150 A, 300 A. Trip condition: trip on overload.
     2. Line currents: 75 A, 75 A, 75 A. Trip condition: no trip but speed falls.
     3. Line currents: 150 A, 150 A, 150 A. Trip condition: fuses blow on short circuit.
     4. Line currents: 0 A, 180 A, 180 A. Trip condition: trip on overload.

ANS.: D

188. The function of the fuses in a motor starter circuit is to provide:
     1. Overload protection.
     2. Under voltage protection.
     3. Short circuit protection.
     4. Open circuit protection.

ANS.: C

189. If the A.C. line current in a generator is doubled, the heating effect in the stator windings will be:
     1. 4 times
     2. Same
     3. Half
     4. Twice

ANS.: A

190. When a large motor load suddenly is disconnected from the switchboard and the generator is AVR controlled, the voltage will:
     1. Initially fall, then reset to the set value.
     2. Initially rise, then reset to the set value
     3. Remain approximately constant, due to governor action.
     4. Remain approximately constant, due to AVR action

ANS.: B

191. Unloading a generator, it is necessary to gradually decrease the load in order to avoid:
     1. Undue overload on the switchboard.
     2. Undue overcurrent
     3. Undue overspeeding.
     4. Undue temperature rise.

ANS.: C

192. The pair of instruments necessary for generator synchronizing are:
     1. Voltmeter and synchro scope
     2. kW meter and frequency meter
     3. Amp-meter and volt-meter
     4. Synchronoscope and kVA-meter

ANS.: A

193. Prior to synchronizing, the generator voltage and frequency are respectively controlled by:
     1. Speed governor and load power factor
     2. Synchro scope and speed governor
     3. Voltmeter and frequency meter
     4. AVR and speed governor

ANS.: D

194. For ideal synchronizing, the phase angle difference between the incomer e.m.f. and the bus bar voltage should be:
     1. 0°
     2. 30° behind
     3. 90° lag
     4. 30° ahead

ANS.: A

195. During synchronizing, the incoming generator should be running slightly “fast” compared to the bus bar frequency. This is to ensure that the:
     1. Incomers reverse power trip is tested
     2. Incomer picks up as a motor
     3. Most rapid synchronizing action is achieved
     4. Incomer picks up as a generator

ANS.: D

196. The correct time to synchronize is usually taken to be when the synchroscope reaches the “5 to 12” position. This to allow for:
     1. Synchroscope pointer time lag
     2. Circuit breaker operating time
     3. Synchroscope error
     4. Generator phase difference error

ANS.: B

197. Generator 1 and 2 are working in parallel. Prime-mover 2 suffers a total fuel loss. The likely outcome is:
     1. 2 generator trips on reverse power
     2. Generator set 1 trips on reverse speed
     3. 1 machine overloads and trips out on overspeed
     4. 1 machine overspeeds and trips out on overload

ANS.: A

198. You have just synchronized a second alternator onto the main switchboard, and want to equally share the load between the “on” and incoming alternators. What would you do first?
     1. Adjust voltage rheostat for the incoming alternator on the front of the switchboard
     2. Lower the governor speed controller of the incoming alternator and increase the governor speed controller of the alternator already on the switchboard
     3. Trip the circuit breaker of the incoming alternator and check the voltage and speed adjustments bef ore trying again
     4. Raise the governor speed controller of the incoming alternator and reduce the governor speed controller of the alternator already on the switchboard

ANS.: D

199. Advantage of Ni Cad battery
     1. no need to top up
     2. no damage due to short circuit
     3. no corrosive/ explosive vapors
     4. all of the above

ANS.: D

200. At which point do you engage the main circuit breaker of the incoming alternator when paralleling two alternators?
     1. With the pointer of the synchronoscope rotating fast and both synchronizing lamps flashing on and off
     2. In none of the mentioned alternatives
     3. With the pointer of the synchronoscope at 0° (12 O’clock) and both synchronizing lamps dark (off)
     4. With the pointer of the synchronizer stopped at any position and both synchronizing lamps bright (on)

ANS.: C

201. With no.1 and no.2 alternators running in parallel and the kW loads equally shared, one alternator is drawing much higher current than the other. What does this indicate?
     1. Alternator frequencies are different and should be adjusted on the governor speed controllers
     2. Alternators are out of phase and should be tripped and paralleled again
     3. One alternator has lost one of its phases
     4. The alternators are not generating the same voltages and should be adjusted on automatic voltage regulator rheostats

ANS.: D

202. With two alternators running in parallel, you wish to stop one. The first step is to:
     1. Remove the load from the alternator to be stopped
     2. Make sure the load is evenly shared
     3. Trip the main circuit breaker
     4. Increase the frequency on the switchboard

ANS.: A                                                  

203. You are paralleling two alternators and the pointer of the synchronoscope slowly stops rotating and remains stopped in one position before the circuit breaker is closed. This would indicate:
     1. The frequency of the incoming alternator is the same as that of the main switchboard
     2. The synchronoscope is not functioning properly and should be checked
     3. The voltage of the incoming alternator is the same as that of the main switchboard
     4. The incoming alternator is in phase with the switchboard, but the frequency is not the same

ANS.: A

204. A 450 volt, 859 kW rated generator has not been in operation for several weeks. Prior to starting, insulation resistance readings are taken. The minimum acceptable insulation resistance reading on the main stator winding to allow you to proceed with running the generator is:
     1. 10 000 000 Ohms
     2. 10 0000 Ohms
     3. 10 000 Ohms
     4. 10 00 Ohms

ANS.: A

205. On regular inspections of alternator windings, it is found that windings are always covered with a heavy oil film coming from the atmosphere surrounding the auxiliary engine. After cleaning with an approved solvent, what do you do?
     1. Take no additional action
     2. Blank off intake air filters
     3. Reinsulate the windings after each cleaning
     4. Improve material of intake air filters

ANS.: D

206. On routine daily inspection you notice that there is a light arcing between an alternator’s carbon brushes and rotor slip rings, with alternator operating at 70% load. Should you:
     1. Increase the tension on the brushes
     2. Reverse the polarity of the excitation voltage at the brush holder connection
     3. Move the position of the brushes around the slip rings to find the correct neutral position
     4. Check the surface of the slip rings, polish if necessary and bed in the brushes

 ANS.: D

207. What is the purpose of the alternator reverse power trip?
     1. To prevent parallel operation if the excitation field voltage is reversed
     2. To prevent the alternator from being paralleled if it is out of phase with the main switchboard
     3. To prevent the alternator from “motoring” by being supplied power from other parallel alternator
     4. None of the above

 ANS.: C

208. If you alter the field excitation voltage of one alternator operating in parallel, this will cause change in that alternators:
     1. Reactive load (kVAR)
     2. Frequency
     3. None of the mentioned alternatives
     4. Active load (kW)

ANS.: A

209. The automatic voltage regulator is used to control the output voltage of the alternator at varying load conditions by:
     1. Varying the excitation field strength by regulating excitation voltage/current
     2. Regulating the voltage signal to the engine governor to regulate the speed to the desired load condition
     3. Supplying variable current to compounding and no load transformers in the alternator stator winding circuit
     4. all of the mentioned alternatives

ANS.: A

210. The power requirements for the excitation winding/circuit for a 3-phase alternator operating at rated output power are supplied by:
     1. Independent battery supply
     2. Independent power supply and rectifier unit
     3. The main switchboard via a three phase rectifier
     4. The alternators output itself via the automatic voltage regulator

ANS.: D

211. A three phase alternator is connected singularly to the main switchboard. The switchboard instruments show 440 Volts/950 amperes. With a power factor of 0.8 what will be the kW load?
     1. 9 KW
     2. 418 KW
     3. 4 KW
     4. 2 KW

 ANS.: D

212. 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:
     1. Prevent charging of capacitive components within the automatic voltage regulator causing false regulation when generator restarts
     2. Prevent operation of automatic voltage regulator during insulation testing
     3. Prevent damage to sensitive electronic components from high voltage tester
     4. Protect insulation resistance tester from being damaged

ANS.: C

213. Following circuits are NOT used in digital computers
     1. AND gate
     2. NOT gate
     3. IF gate
     4. OR gate

ANS.: C

214. Megger readings versus temperature – 1 mega ohm at 75◦c is equivalent to how much at 25◦c.
     1. 1 mega ohm — no change
     2. 30 mega ohms
     3. 2 mega ohms
     4. 7 mega ohms

ANS.: B

215. The black terminal probe of the multimeter is
     1. positive terminal
     2. negative terminal
     3. common terminal
     4. earth terminal

ANS.: C

216. A star delta starter
     1. used for large motors like bow thruster
     2. starting torque and starting current reduced to 1/3
     3. long starting time
     4. all of the above

ANS.: D

217. Direct on line starter
     1. less time taken
     2. can be started at full load
     3. starting current is 7 times more than full load current
     4. all of the above

 ANS.: D