Description : In the illustration, the purpose of part B is to _________. EL-0033 A. increase resistance in series with the contacts as they close to prevent arcing B. create a magnetic field in the steel ... event of an overload D. provide ventilation to the contact when the breaker is close to rated capacity
Last Answer : Answer: B
Description : An AC generator operating in parallel loses its excitation without tripping the circuit breaker. This will __________. A. not affect the faulty generator due to the compensation of the other generators B. ... between the armature and the bus D. cause high currents to be induced in the field windings
Last Answer : Answer: D
Description : When securing an AC generator, you should FIRST ___________. A. open the generator circuit breaker B. switch the voltage regulator to 'manual' C. decrease the field excitation to minimum D. reduce the load on the unit
Description : The arc resulting from the tripping of a circuit breaker is prevented from damaging the contacts by _____________. A. designing the contacts to open slowly B. directing the arc into an ... an inverse timed thermal trip for short circuit currents D. instantaneous magnetic trip for overload currents
Description : A molded-case circuit breaker provides protection against short circuits by using a/an ________________. A. electromagnet B. shading coil C. arc quencher D. burn away strip
Last Answer : Answer: A
Description : A molded-case breaker provides protection against short circuits by using a/an ____________. A. shading coil B. arc quencher C. electromagnet D. holding coil
Last Answer : Answer: C
Description : In an AC generator, direct current from a separate source is passed through the windings of the rotor _____________. A. by means of slip rings and brushes B. by means of a commutator C. by means of rotating bar magnet D. to minimize the danger of arc over
Description : Voltage failure of an AC generator may be caused by ____________. A. failure of the exciter generator B. a tripped bus circuit breaker C. high mica segments on the stator bus bar D. excessive prime mover speed
Description : An alternator will fail to produce line voltage as a result of _____________. A. a closed circuit breaker B. oxidized slip rings C. improperly staggered brushes D. exciter generator failure
Description : In order to safely carry out repairs to a generator circuit breaker, it must be isolated from the bus. This is accomplished by opening the _____________. A. reverse power relay B. bus disconnect link C. generator bus fuse connections D. power directional relay
Description : As a result of a mechanical malfunction in one of the ship's service generators operating in parallel, you must secure that generator. In order to prevent a possible overload to the ... feeder circuit breakers, the malfunctioning prime mover turbine throttle trip, and the generator circuit breaker.
Description : Attempting to parallel an AC generator which is out of phase with the bus will result in which of the following problems? A. The breaker should trip. B. The KVA will decrease. C. The synchronizing lamps will burn out. D. The power factor will be unitized.
Description : In the illustration, the contacts between terminals 26 and 27 should be closed when _________. EL-0046 A. using one generator in isochronous mode only B. using two or more generators in ... through varying loads in parallel or single operation D. the circuit breaker is closed for that generator
Description : When paralleling two AC generators, the frequency (cycles) of the incoming generator, just prior to closing the circuit breaker, should be _____________. A. slightly less than the frequency of the generator on ... C. slightly more than the frequency of the generator on the line D. all of the above
Description : When paralleling two AC generators, the frequency of the machine coming online, immediately prior to closing its breaker, should be ____________. A. slightly less than the oncoming generator frequency B. the ... bus frequency C. slightly greater than the bus frequency D. the same as the bus voltage
Description : Undervoltage trips are frequently installed on switchboard circuit breakers to trip ____________. A. out generators in the event of severe arcing or sparking B. out generators when there is reversal of power ... , but continues to run D. out generators when there is low voltage in the main circuit
Description : An AC generator panel is fitted with both synchronizing lamps and a synchroscope. When the synchroscope pointer reaches the noon position, one synchronizing light is bright and the other is dark. This ... sequence is incorrect C. the phase sequence is correct D. the generator breaker may be closed
Description : A reverse-current relay will prevent AC generator motorization by ____________. A. automatically redirecting the load B. automatically speeding up the prime mover C. tripping the panel board main switch D. tripping the generator circuit breaker
Description : The devices labeled 'L' in the illustration are _________. EL-0003 A. load lights indicating that the generator breaker is closed and the generator is supplying power to the main bus B. ... o'clock position the lights are at their dimmest or out indicating the the generators are in phase
Description : A bus disconnect link is used to isolate _____________. A. one bus bar from another B. the generator circuit breaker from the bus C. different phases from the equalizer connection D. positive and negative buses from the neutral
Description : Arc in a circuit breaker is interrupted at (a) zero current (b) maximum current (c) minimum voltage (d) maximum voltage
Last Answer : (a) zero current
Description : The arc voltage produced in A.C. circuit breaker is always (a) in phase with the arc current (b) lagging the arc current by 90" (c) leading the arc current by 90° (d) none of the above
Last Answer : (a) in phase with the arc current
Description : In a circuit breaker the basic problem is to (a) maintain the arc (b) extinguish the arc (c) transmit large power (d) emit the ionizing electrons
Last Answer : (c) transmit large power
Description : The voltage appearing across the contacts after opening of the circuit breaker is called______voltage. (a) recovery (b) surge (c) operating (d) arc (e) none of the above
Last Answer : (a) recovery
Description : Which of the following medium is employed for extinction of arc in air circuit breaker ? (a) Water (b) Oil (c) Air (d) SF6
Last Answer : (c) Air
Description : Which of the following medium is employed for extinction of arc in air circuit breaker ?(a) Water (b) Oil(c) Air (d) SF6
Last Answer : Which of the following medium is employed for extinction of arc in air circuit breaker ?(a) Water (b) Oil(c) Air (d) SF6
Description : The arc temperature in Oil Circuit Breaker may reach up to_______. (A) 5,000° K (B) 8,000° K (C) 10,000° K (D) None of the above
Last Answer : The arc temperature in Oil Circuit Breaker may reach up to 5,000° K
Description : The arc voltage in a circuit breaker is :
Last Answer : The arc voltage in a circuit breaker is : in phase with the arc current
Description : Which of the following is used in a circuit breaker as the medium in which the arc forms? A) Insulating gas B) Insulating oil C) Vacuum D) All the above
Last Answer : Which of the following is used in a circuit breaker as the medium in which the arc forms? A) Insulating gas B) Insulating oil C) Vacuum D) All the above
Last Answer : Arc in a circuit breaker is interrupted at zero current.
Last Answer : The arc voltage produced in A.C. circuit breaker is always in phase with the arc current.
Description : When molten sulphur is quenched, the following is formed.
Last Answer : When molten sulphur is quenched, the following is formed. A. Monoclinic sulphur B. Rhombic sulphur C. Crystex(plastic) D. `gamma`-sulphur
Description : A solid aluminium ball, when quenched in a water bath maintained at 40°C, cools down from 550°C to 450°C in 20 seconds. The expected temperature of the ball after next 20 seconds may be about __________ °C. (A) 370 (B) 340 (C) 320 (D) 300
Last Answer : (A) 370
Description : 5. In "Imperial Smelting Process" for extraction of zinc, zinc vapour thus produced is quenched in the external condenser by the use of the following: (A) Jet of water at high pressure (B) Blast of air (C) Mixture of water and air (D) Rain of molten lead
Last Answer : Option D
Description : Wrought metal is to be, A. Marble B. Quenched C. Subjected /undergone/ to cold treatment during processing (annealed)
Last Answer : C. Subjected /undergone/ to cold treatment during processing (annealed)
Description : You are attempting to parallel two AC generators and the synchroscope pointer is revolving slowly in the fast direction. You should _____________. A. use the governor control switch to adjust the incoming ... the 0° position D. use the field rheostat to adjust the speed of the incoming machine
Description : A ground can be defined as an electrical connection between the wiring of a motor and its ____________. A. shunt field B. circuit breaker C. metal framework D. interpole
Description : How over voltage is produced in Field breaker?
Last Answer : Over voltages appear if synchronous generators and motors fall out of step inducing an AC voltage in the field system. Depending on the type of construction of the machine and the slip this ... -permissibly high, for this purpose over voltage protectors are provided in the field breaker cubicle.
Description : What are the logics adopted to close the field breaker?
Last Answer : a) Turbine speed 2880 rpm. b) Class A, B and BG trip reset. c) Auto/manual reference minimum. d) Auto/manual channels supply normal. e) FB closing circuit healthy.
Last Answer : The type of dc generator used for arc welding purposes is a Differentially compound generator.
Description : After a black out the emergency generator comes on; On restoring the main supply we are closing the circuit breaker of the main generator without bothering about synchronizing. How is this possible?
Last Answer : There is a power link connection breaker between the main generator and the emergency generator. During black out, this breaker trips. The emergency generator starts and its breaker closes and feeds only ... , there is no paralleling between main and emergency generator. Ask E/O for more details.
Description : Moving the rheostat handle shown in the illustration, that is used to control a DC generator, towards the 'raise' direction will increase the _____________. EL-0030 A. field resistance B. armature resistance C. armature speed D. line voltage
Description : As shown in the illustration, the generator field is excited with DC current provided by ____________. EL-0016 A. conductors '1', '2' and '3' B. inductor 'L1' C. rectifier 'CR1' D. winding 'S-2'
Description : The most common type of AC service generator found aboard ship is the stationary _____________. A. electromagnetic field, revolving armature type B. electromagnetic field, oscillatory armature type C. armature, oscillatory electromagnet field type D. armature, rotating electromagnetic field type
Description : A loss of field excitation to an AC generator while operating in parallel will cause it to ____________. A. absorb more and more load due to decreased armature reaction B. lose its load due to ... polarity D. lose its load, begin to motorize, trip out on reverse power relay, and possibly overspeed
Description : An open occurring within the field rheostat of an AC generator can be detected by short circuiting its terminals and observing a ____________. A. negative deflection of the wattmeter pointer B. ... of the wattmeter pointer C. buildup of alternator voltage D. low, but constant alternator voltage
Description : If an AC generator experiences voltage failure, the cause may be _____________. A. an open in the field circuit B. the brushes shifting out of the neutral plane C. excessive locked-rotor current D. a rotating slip ring
Description : Which of the listed electrical devices is represented by the symbol shown in the illustration? EL-0055 A. Fixed resistance resistor B. Coil with magnetic core C. DC motor or generator shunt field D. Transformer
Description : Moisture accumulating in electric motors and generator windings having a cold insulation resistance greater than 50,000 ohms may be baked out with internal heat. This heat can be developed by ____________. ... an electric welder and feeding it into the armature while running the motor at full speed
Description : If the connections for the field and the armature on a DC motor are reversed, _____________. A. the motor will run as a generator B. the motor will not run C. the direction of rotation will be the same D. the direction of rotation will be reversed