Description : The speed of a three-phase squirrel-cage induction-type motor operating in a fixed frequency system is varied by changing the _____________. A. number of phases to the motor B. number of stator poles C. locked rotor current D. resistance of the rotor winding
Last Answer : Answer: B
Description : A characteristic of a wound-rotor induction motor, with a high resistance rotor winding, is _____________. A. low starting torque B. high starting torque C. high speed D. low starting voltage
Description : The torque produced by a motor when its shaft will not turn, even though rated voltage is applied to the stator, is known as _____________. A. locked-rotor torque B. pullout torque C. breakdown torque D. torque margin
Last Answer : Answer: A
Description : If the energy input is significantly reduced to the prime mover of one shipboard alternator operating in parallel with others, that alternator will _____________. A. continue to operate at no load B. lose ... overspeed C. begin to motorize and then trip out D. slow down and operate at reduced load
Last Answer : Answer: C
Description : The purpose of a cage rotor winding placed on the rotor of a synchronous motor is to _____________. A. provide excitation to the DC field B. start the machine as an induction motor C. contribute extra torque at synchronous speed D. prevent the machine from falling out of step
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 : A characteristic of an induction motor with a low resistance rotor winding is _____________. A. high starting voltage B. high starting current C. high slippage D. low starting voltage
Description : A megger is being used to test the insulation of an AC generator. The resistance value of a dry, clean winding will _____________. A. continue to rise as test potential is maintained, ... , becoming fairly steady after 5-7 minutes D. stabilize after approximately 2-4 minutes of fluctuation
Description : Motor name plate data includes '°°C rise'. This indicates the _____________. A. actual running temperature of the winding from no load to full load B. permissible temperature rise ... above normal full load operating temperature D. maximum allowable temperature rise for continuous no load service
Description : The function of the autotransformers used with the starters of large AC motors is to provide _____________. A. increased voltage for starting B. increased torque for starting C. reduced voltage for starting D. speed control
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 : Using illustrated chart, when will the power factor be least efficient? EL-0006 A. When the motor is operating at full load. B. When the percentage of slip is greatest. C. When there is no load on the motor. D. the power factor is the same from no-load to locked rotor.
Description : In the construction of D.C. motors, parts of both the series and shunt fields are wound on the _____________. A. opposite main pole B. rotor core C. interpole D. same main pole
Last Answer : Answer: D
Description : The air gap provided in induction motors should be checked periodically with a feeler gage to detect an unequal air gap and _____________. A. decreased motor magnetizing current B. hysteresis loses C. increased power factor D. mechanical damage to the rotor
Description : The speed of a squirrel cage induction motor is determined by the _____________. A. diameter of the stator B. number of stator poles C. rotor winding resistance D. bar resistance of the conducting rotor
Description : If the residual flux is absent in the rotor iron of the isolated induction generator, a) it will not run. b) it will run as induction motor c) it will burn the winding d) it will not affect the characteristic of the generator
Last Answer : Ans: A
Description : You are testing the insulation in an AC generator with a megohmeter. The resistance value of a dry, clean winding will ____________. A. continue to rise as the test potential is maintained, ... fairly steady after 5 to 7 minutes D. stabilize after approximately 2 to 4 minutes of fluctuation
Description : Power transformers are rated in _____________. A. kilowatts B. ampere-turns C. kilowatt-volts D. kilovolt-amperes
Description : Autotransformer starters or compensators are sometimes used with polyphase induction motors to _____________. A. reduce the voltage applied to the motor during the starting period B. increase the voltage for ' ... to be either stepped up or down, depending on the application, to ensure full torque
Description : Regarding an induction motor, the power developed by the rotor automatically adjusts itself to the _____________. A. power required to drive the load B. speed required to drive the load C. current flow in the motor stator D. torque developed by the rotating field
Description : Which of the following is a characteristic of fractional horsepower repulsion start motors? A. They start with a rotating stator field. B. The short circuiting ring is removed from the commutator while ... brushes are removed from the commutator while starting. D. They have a low starting torque.
Description : If the centrifugal switch or relay used for cutting out the starting winding of a split-phase induction motor fails to open once the motor is in operation, the _____________. A. motor will overspeed B ... C. motor will immediately stall under load D. motor torque will be above normal at rated speed
Description : What is the purpose of each of the 'signal conditioners' (6000F085 / AH170 / F125) shown in the illustration? EL-0094 A. Convert the varying signal from its particular sensor and deliver a ... the 'setpoint module' in order to keep the pressure or temperature at its sensor at set limits.
Description : Which of the following operating characteristics for DC motors is considered to give high starting torque? A. series B. shunt C. cumulative-compound D. differential-compound
Description : If the driving torque, such as that produced by a diesel engine, creates pulsations when coupled with a synchronous generator operating in parallel; the generator rotor may be periodically pulled ahead or behind ... as it rotates. This co A. hunting B. direct coupling C. peaking D. harmonic coupling
Description : If the driving torque, such as that produced by a diesel engine, creates pulsations when coupled with a synchronous generator operating in parallel; the generator rotor may be periodically pulled ... windings B. direct coupling C. increase governor speed droop D. decreasing governor speed droop
Description : The shipboard general alarm system must receive its main source of power from _____________. A. a storage battery B. the emergency generator C. an auxiliary generator D. the ship's service generator
Description : When shipboard electrical distribution circuits are connected in parallel, additional parallel circuits will cause the total circuit resistance to _____________. A. increase, causing a drop in the line current B ... an increase in the line voltage D. decrease, causing an increase in the line current
Description : The part of the shipboard electrical system used to control the distribution of power to the branch circuits, is the _____________. A. bridge control panel B. disconnect links C. governor relay box D. main switchboard
Description : The cross-sectional area of shipboard electrical cable is expressed in _____________. A. millimeters B. gage numbers C. centimeters D. circular mils
Description : An advantage of DC motors over AC motors is that they _____________. A. are less expensive B. require less maintenance C. offer infinite speed variation D. all of the above
Description : Universal motors will operate on AC or DC current, and are generally found in _____________. A. portable tools B. large pump motors C. turbo electric main motors D. forced draft fans
Description : An advantage of DC motors over AC motors is that they _____________. A. are less expensive B. require less maintenance C. can be started across the line D. offer a more effective means of controlling speed
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 : 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 reactive power drawn by a motor from an AC generator is the power which is _____________. A. used to establish the magnetic field of the motor B. lost in overcoming friction in the ... by current flow through the windings D. transmitted directly through the rotor shaft to perform useful work
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 : The hook-on AC volt-ammeter consists essentially of a split-core and a rectifiertype instrument connected to the secondary winding of a _____________. A. potential transformer B. control transformer C. current transformer D. reactance transformer
Description : Basically, a magnetic amplifier is a saturable reactor with the addition of _____________. A. AC to the bias winding B. variable capacitance to all windings C. eddy current protectors D. a rectifier in the load circuit
Description : Ambient temperature is the _____________. A. amount of temperature rise with no load B. amount of temperature developed by an operating motor C. temperature of the compartment where the motor is located D. normal operating temperature, less the room temperature
Description : Ambient temperature is the _____________. A. amount of temperature rise with no load B. temperature of the compartment where the motor is located C. normal operating temperature, less the room temperature D. amount of temperature developed by an operating motor
Description : The speed of a multi-speed, squirrel-cage, induction motor operating in a fixed frequency system can be changed by _____________. A. reconnecting stator windings for different numbers of poles B. ... sequence of the applied voltage D. reconnecting the stator so that no poles have the same polarity
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
Description : The device in figure 'B' shown in the illustration can be used to control an AC load yet maintain its high gain by ______________. EL-0091 A. connecting the load to the output side of the ... connecting the load to the input side of the bridge D. reversing the current flow through the bias winding
Description : Routine A.C. motor maintenance should include periodic ______________. A. thermometer readings at normal loads to detect abnormal temperature rises B. inspection of the motor's internals for loose rotor bars ... C. bearing replacement each year using sealed units if available D. all of the above
Description : The operating torque of the upper induction disc-type element, or timer element, of an AC reverse power relay is obtained from ____________. A. the main bus B. a separate battery source C. line voltage D. electromagnets
Description : The purpose of the bias winding in figure 'B' shown in the illustration is for ____________. EL-0091 A. changing the direction of current in the control winding B. setting the operating point of the ... use of either AC or DC in the load circuit D. changing the direction of current through the load
Description : If 450 volts AC were measured across the load as shown in the illustration it would indicate a/an _______________. EL-0083 A. open winding between 'H1' and 'X1' B. properly operating circuit C. open winding between 'X1' and 'X4' D. ground on one side of 'Ep'
Description : Excessive heat in an operating motor controller can result from _____________. A. a closed starter contact B. loose connections C. missing arc chutes D. low motor starting torque
Description : The timer element found in a reverse power relay obtains its operating torque via _____________. A. line voltage B. the main bus C. electromagnets D. a separate battery source