Description : The voltage output of an AC generator is accurately controlled by _____________. A. changing the sensitivity of the prime mover to large changes in voltage B. varying the reluctance of the air gap C. varying the DC exciter voltage D. shorting out part of the armature windings
Last Answer : Answer: C
Description : The frequency of an alternator at a given RPM is determined by the _____________. A. number of turns of wire in the armature coil B. number of magnetic poles C. strength of the magnets used D. output voltage
Last Answer : Answer: B
Description : The frequency output of an operating alternator is controlled by the _____________. A. relative speed of the rotor poles B. number of turns of wire in the armature coil C. strength of the magnets used D. output voltage
Last Answer : Answer: A
Description : A DC generator is used to supply direct current in order to maintain an AC generator field and is known as a/an _____________. A. rotor B. stator C. exciter D. armature
Description : The output voltage of a 440 volt, 60 hertz, AC generator is controlled by the _____________. A. prime mover speed B. exciter output voltage C. load on the alternator D. number of poles
Description : An electrical device which employs a stationary armature and a rotating electromagnetic field is used aboard ship as a ____________. A. magnetic amplifier B. ship's service alternator C. three-wire DC generator D. saturable core reactor
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
Last Answer : Answer: D
Description : DC generator voltage is decreased by cutting _____________. A. in field resistance B. out field resistance C. in armature resistance D. out armature resistance
Description : The purpose of the commutator and brushes on a DC generator is to _____________. A. transfer generated direct current voltage from the armature to the line B. convert the alternating voltage ... contact method to excite the field D. reduce sparking between the armature and the carbon brushes
Description : When three-phase AC power is supplied to the device shown in the illustration, the output will be _____________. EL-0063 A. single-phase AC B. split-phase AC C. three-phase DC D. unidirectional DC
Description : AC and DC generators are similar in that they _____________. A. both generate alternating voltages B. both rectify the voltage before delivery C. are constructed at the same physical size for the same kilowatt rating D. both supply three-phase power
Description : A change in field excitation of an alternator operating in parallel will cause a change in its _____________. A. alternator frequency B. kilowatt load C. voltage output D. all of the above
Description : The standard method of controlling the output voltage of a 440 volt, 60 Hz, AC generator is accomplished by adjusting the ____________. A. prime mover speed droop B. number of poles C. alternator field excitation D. load on the alternator
Description : One factor that determines the frequency of an alternator is the ____________. A. number of turns of wire in the armature coil B. number of magnetic poles C. strength of the magnets used D. output voltage
Description : The purpose of DC generator brushes is to _____________. A. neutralize armature reaction B. conduct electric current to an outside circuit C. convert DC current to AC current D. provide excitation to a DC generator
Description : A short in the shunt field of a DC motor is best located by _____________. A. visual inspection of the commutator B. applying AC voltage to each field coil and measuring the voltage drop across ... using a growler and hacksaw blade D. isolating each coil from the others and using a megohmmeter
Description : A three-phase synchronous motor has a terminal voltage of 460 V and a terminal current of 120 A at a power factor of 0.95 lagging, synchronous reactance of 1.68 ohm and the field current is 47 A. The field to armature mutual ... _____________. (a). 20mH (b). 16mH (c). 24mH (d). 22mH
Last Answer : 22
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
Description : If you reverse both the field and the armature connections to a DC propulsion motor, _____________. A. the direction of motor rotation will change B. the brushes will become overheated C. a magnetic lock will occur in the motor D. the direction of motor rotation will remain the same
Description : A shunt-wound DC generator is one in which the shunt field windings are in parallel with the _____________. A. commutator B. brushes C. armature D. all of the above
Description : A DC shunt generator has its field windings connected in _____________. A. series with the series windings B. parallel with the field rheostat C. series with the armature windings D. parallel with the armature windings
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 : The most practical way to control the voltage output of an AC generator is to vary the _____________. A. number of windings B. speed of the rotating field C. strength of the rotating magnetic field D. power factor of the load
Description : The voltage of an operating AC turbogenerator is raised or lowered by adjusting the _____________. A. exciter generator governor controls B. synchronizing switch C. phase sequence switch D. generator field exciter
Description : The output voltage of a 440 volt, 60 Hz AC generator is controlled by the ______________. A. load on the alternator B. load on the prime mover C. speed of the prime mover D. exciter output voltage
Description : If field excitation is suddenly lost to an alternator operating in parallel, that alternator will _____________. A. supply excessive current to the bus B. operate at the same load, but with reduced voltage C. lose its load and tend to overspeed D. become overloaded and slow down
Description : The cycles per second developed by the alternator aboard your vessel is determined by _____________. A. the speed of the engine driving the alternator B. the resistance applied to the field rheostat C. the synchronous speed of induction D. the adjustments made to the voltage regulator
Description : Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in ... . governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay
Description : The direction of rotation of the winch shown in the illustration is changed by reversing the _____________. EL-0102 A. direction of current through the shunt field B. polarity of voltage at 'S1' and 'S2' C. direction of current through the armature D. polarity of voltage at 'L1' and 'L2'
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 : 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 : 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
Description : The electrical supply applied to the anodes shown in the illustration is _____________. EL-0090 A. low voltage, high current DC B. low voltage, high current AC C. high voltage, low current DC D. high voltage, low current AC
Description : The most common source of excitation for synchronous motors is a/an _____________. A. low voltage battery B. motor attenuator set C. DC exciter generator D. AC supply
Description : Across-the-line starters are used with AC motors to provide _____________. A. reduced starting current B. regulated starting current C. high starting torque D. controlled starting acceleration
Description : A three-phase alternator is operating at 450 volts, 250 amps at 0.6 power factor. If the power factor increases to 0.8, the kw load potential will increase by _____________. A. 38.525 kw B. 116.91 kw C. 155.88 kw D. 194.85 kw
Description : The torque produced by a DC motor armature is the product of the force acting at the armature surface multiplied by _____________. A. work done by the armature in one revolution B. effective ... arm at the center of rotation of the armature D. perpendicular distance to its center of rotation
Description : A shorted armature coil in a DC motor can be detected by _____________. A. sparking at the brushes B. shiny armature coil C. worn grooves in the armature D. undercut mica
Description : A short circuit in the armature of a DC motor will cause the motor to _____________. A. run fast B. hum when energized C. spark at the brushes D. fail to start
Description : A flickering ground detection lamp on a DC system would indicate a _____________. A. multiple-ground condition in the distribution system B. ground in an armature coil of an operating machine C. ground in a motor accompanied with a short D. short between two adjacent bars of the generator commutator
Description : Temporary repairs to an open DC propulsion armature coil can be made by _____________. A. connecting the coil ends directly to a pair of negative brushes B. disconnecting coil ends, insulating ... C. grounding the coil ends and short circuiting the commutator bar D. removing the sparking brushes
Description : Armature cores in a DC generator are made of laminated steel sheets to _____________. A. fit the curvature of the frame B. increase the hysteresis effect C. reduce eddy current losses D. allow for easy assembly
Description : Transformers are used onboard ships with AC generators to _____________. A. change frequency B. increase power output to modulating frequency controllers C. decrease power output to modulating frequency ... D. permit higher voltage for electric motor operation and low voltage for lighting circuits
Description : A constant output voltage from an AC generator is maintained by the _____________. A. prime mover governor B. exciter generator C. voltage regulator D. reverse power relay
Description : Three factors responsible for the change in voltage as load is applied to an AC generator are: 1) the drop in resistance in the armature circuit, 2) the change in flux, and 3) the ____________. A. armature winding speed B. inductance load drop C. coil pitch factor D. armature reactance voltage drop
Description : Why shading rings provided in armature core of ac contactor. Why not for dc contactor?
Last Answer : Because the force developed is not steady in ac therefore contacts will chatter but if shading ring is used force developed becomes steady due to splitting of phases of flux, therefore contacts becomes bounce free and humming sound reduces.
Description : Which of the following are the parts of a DC generator that convert the AC in the armature to DC in the external circuit. Are these parts the: w) field poles x) slip rings and the brushes y) commutator and the brushes z) armature and the core
Last Answer : ANSWER: Y -- COMMUTATOR AND THE BRUSHES
Description : The number of cycles per second occurring in AC voltage is known as the _____________. A. phase angle B. frequency C. wave form D. half mode
Description : In a three-phase, squirrel-cage type, induction motor the rotating magnetic field is established by the _____________. A. current induced in the rotor windings B. application of a three-phase voltage ... caused by the induced current in the squirrel-cage bars with the magnetic field of the stator
Description : In the illustration, the component labeled 'EXC' is _______. EL-0003 A. a separate class II regulated DC generator for critical direct current loads B. a generator feeding the FLD ... to drive the governor for turbogenerator speed. D. the electronic driver for the switchboard metering circuits