Description : What will happen if the induction motor runs at synchronous speed ?
Last Answer : Since there is always slip present in rotor it cannot run at synchronous speed no current will be developed hence no torque will developed
Description : If the field circuits of an unloaded salient pole synchronous motor gets suddenly open circuited, then (A) The motor stops. (B) It continues to run at the same speed. (C) Its runs at the slower speed. (D) It runs at a very high speed.
Last Answer : Ans: B The motor continues to run at the same speed because synchronous motor speed does not depend upon load, Nα f.
Description : A four-pole 60-hertz induction motor has a synchronous speed of 1800 RPM and a slip of 4 percent at full load. What will be its full load speed? A. 1728.0 RPM B. 1730.7 RPM C. 1800.0 RPM D. 1872.0 RPM
Last Answer : Answer: A
Description : If the synchronous speed of a 12 pole, polyphase, induction motor operating at 60 Hz were 600 RPM, how many poles will be required in a similar motor operating at the same frequency but having a synchronous speed of 900 RPM? A. 4 B. 6 C. 8 D. 18
Last Answer : Answer: C
Description : If an induction motor were to be operated at 90% rated voltage, _____________. A. there would be an increase in starting torque B. starting current would increase slightly C. synchronous speed would decrease slightly D. the slip would increase
Last Answer : Answer: D
Description : The speed of a wound-rotor induction motor _____________. A. will be fixed by the number of field poles B. can be varied by a rheostat-type control C. can only be synchronous speed at full load D. can only attain synchronous speed at no load
Last Answer : Answer: B
Description : The synchronous speed of an induction motor is the ________. A. speed at which the rotor turns B. speed of the rotating field C. frequency of the rotor current D. slip in per cent of rotor RPM
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 : A motor using a rheostat in the motor circuit to vary the speed is called a ____________. A. squirrel-cage induction motor B. regenerative braking motor C. wound-rotor induction motor D. synchronous motor
Description : The synchronous speed for a 3 phase 6-pole induction motor is 1200 rpm. If the number of poles is now reduced to 4 with the frequency remaining constant, the rotor speed with a slip of 5% will be _________. (A) 1690 rpm (B) 1750 rpm (C) 1500 rpm (D) 1710 rpm
Last Answer : (D) 1710 rpm
Description : Synchronous motor always runs at which speed?
Last Answer : Synchronous motor always runs at synchronous speed.
Description : A four pole, 60 Hz, three-phase synchronous motor comes up to 1760 RPM when started as an induction motor. What is the percent slip after the rotor field is energized? A. 0 B. 1.1 C. 2.2 D. 3.3
Description : Which of the listed motors will operate at the highest RPM, assuming that each operates at the same frequency? A. A four-pole synchronous motor under normal load. B. A four-pole induction motor under ... A six-pole synchronous motor under normal load. D. A six-pole induction motor under full load.
Description : A shaded-pole motor is a ____________. A. synchronous motor B. three-phase induction motor C. compound-wound motor D. single-phase induction motor
Description : Which of the following statements is true concerning a polyphase synchronous propulsion motor? A. The motor is started as an induction motor. B. Resistance is gradually added to the rotor circuit. C. ... is held below the rated current. D. The field winding is energized for starting purposes only.
Description : Which motor has high Starting Torque and Staring current DC motor, Induction motor or Synchronous motor?
Last Answer : DC Series motor has high starting torque. We can not start the Induction motor and Synchronous motors on load, but can not start the DC series motor without load.
Description : Which Motor Has High Starting Torque And Staring Current Dc Motor, Induction Motor Or Synchronous Motor?
Description : The drive motor used in a mixer-grinder is a (A) dc motor. (B) induction motor. (C) synchronous motor. (D) universal motor.
Last Answer : Ans: D The universal motor is suitable for AC & DC both supply systems.
Description : A motor which can conveniently be operated at lagging as well as leading power factors is the (A) squirrel cage induction motor. (B) wound rotor induction motor. (C) synchronous motor. (D) DC shunt motor.
Last Answer : (C) synchronous motor.
Description : The synchronous speed of an 8 pole induction motor supplied power from a 50 Hz source will be ?
Last Answer : Ns equals f/pair pole 50/4 - 12.5
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 : The difference between the synchronous speed of an induction machine and its operating speed (slip) may be correctly expressed _____________. A. as a percent of synchronous speed B. as a decimal fraction of synchronous speed C. directly in revolutions per minute D. as all of the above
Description : The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a (A) dc machine. (B) 3 phase induction machine. (C) synchronous machine. (D) single phase induction machine.
Last Answer : Ans: all options are correct
Description : in a three-phase induction motor, the rotor field runs at the following speed with respect to the stator structure:
Last Answer : in a three-phase induction motor, the rotor field runs at the following speed with respect to the stator structure: At synchronous speed in the direction of stator field
Description : A 3-phase, 4-pole, 50Hz induction motor runs at a speed of 1440 rpm. The rotating field produced by the rotor rotates at a speed of ________ rpm with respect to stator field. (A) 1500 (B) 0 (C) 1440 (D) 60
Last Answer : 0
Description : The effect of carrying field excitation excessively high on a synchronous motor will result in a _____________. A. tendency for the motor to fall out of step B. tendency for the motor to overspeed C. tendency for the motor to overheat D. loss of motor speed regulation
Description : The speed of a synchronous motor is varied by _____________. A. interchanging any two of the three live leads B. changing the voltage of the system C. changing the input frequency D. increasing the field excitation
Description : The propeller shaft speed in a turbo-electric, synchronous, propulsion drive motor is changed by varying the __________. A. turbine speed B. number of motor poles C. field strength of the generator D. field strength of the motor
Description : An increase in which of the listed conditions will increase the speed of a synchronous motor? A. Frequency B. Voltage C. Armature current D. Inductance
Description : In an AC synchronous motor electric propulsion plant, propeller speed is controlled by varying the _____________. A. prime mover speed B. electric coupling field strength C. number of energized main motor poles D. propulsion generator field strength
Description : Why a synchronous motor is a constant speed motor?
Last Answer : When load increase in synchronous motor the load angle δ also increases but speed remains constant. The further increase in load cause further increase in load angle. When load angle reaches ... out of synchronism. Hence the motor rotates at synchronous speed otherwise it comes out of synchronism.
Description : What is the effect on speed if the load is increased on a 3 phase synchronous motor?
Last Answer : The speed of operation remains constant from no load to maximum load in the motor operating at constant frequency bus bars.
Description : A single phase Hysteresis motor (A) can run at synchronous speed only (B) can run at sub synchronous speed only (C) can run at synchronous and super synchronous speed (D) can run at synchronous and sub synchronous speed
Last Answer : Ans: A The rotor revolves synchronously because the rotor poles magnetically lock up with the revolving stator poles of opposite polarity
Description : The speed-torque characteristics of a DC series motor are approximately similar to those of the _________motor. (A) universal (B) synchronous (C) DC shunt (D) two-phase
Last Answer : Ans: A Universal motor has same characteristics as DC series motor and also known as an a.c series motor.
Description : In a 3-phase synchronous motor (A) the speed of stator MMF is always more than that of rotor MMF. (B) the speed of stator MMF is always less than that of rotor MMF. (C) the speed of ... speed while that of rotor MMF is zero. (D) rotor and stator MMF are stationary with respect to each other.
Last Answer : Ans: D Because, Motor is magnetically locked into position with stator, the rotor poles are engaged with stator poles and both run synchronously in same direction Therefore, rotor & stator mmf are stationary w.r.t each other.
Description : When a synchronous motor is running at synchronous speed, the damper winding produces (A) damping torque. (B) eddy current torque. (C) torque aiding the developed torque. (D) no torque.
Last Answer : (D) no torque.
Description : A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will (A) come to stop. (B) continue to run at synchronous speed. (C) continue to run at ... more than the synchronous speed. (D) continue to run at a speed slightly less than the synchronous speed.
Last Answer : (B) continue to run at synchronous speed.
Description : A d.c. shunt motor runs at no load speed of 1140 r.p.m. At full load, armature reaction weakens the main flux by 5% whereas the armature circuit voltage drops by 10%. The motor full load speed in r.p.m. is (A) 1080 (B) 1203 (C) 1000 (D) 1200
Last Answer : (A) 1080
Description : What are the differences between synchronous and induction motor?*
Last Answer : Synchronous motor : Constant speed on all loads, can be operated on a wide range of power factors, not self starting, requires dc excitation.
Description : The length cf air gap to be provided in ______ is primarily determined by power factor consideration. (a) d.c. series motor . (b) d.c. shunt motor (c) induction motor (d) synchronous motor
Last Answer : (c) induction motor
Description : Synchronous wattage of induction motor means: A) rotor input in watts B) stator input in watts C) combined stator and rotor input in watts D) shaft output in watts
Last Answer : Synchronous wattage of induction motor means: rotor input in watts
Description : A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because?
Last Answer : A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because stator supply is not required to produce magnetic field.
Description : Which motor have more efficiency, synchronous motor or induction motor?
Last Answer : Synchronous motor has more efficiency.
Description : Induction generator a) can not work in isolation b) can work in isolation c) should work in parallel with synchronous generators d) any of the mentioned
Last Answer : Ans: C
Description : Which of the following types of motors is often designed for use in correcting power factor? A. Polyphase B. Wound-rotor C. Induction D. Synchronous
Description : An 8-pole alternator runs at 750 rpm and supplies power to a 6-pole induction motor which has a full load slip of 3 percent. The full load speed of the induction motor will be: A) 1000 rpm B) 920 rpm C) 950 rpm D) 970 rpm
Last Answer : An 8-pole alternator runs at 750 rpm and supplies power to a 6-pole induction motor which has a full load slip of 3 percent. The full load speed of the induction motor will be: 970 rpm
Last Answer : If a single phase induction motor runs slower than normal, the most likely defect is worn bearings.
Description : A 3 phase 50 Hz induction motor has full load speed of 970 rpm. Calculate no of poles and slip frequency.
Last Answer : The number of poles in an induction motor can be calculated using the following formula: No. of poles = (120 * frequency) / speed In this case, the number of poles would be calculated as follows: No. of poles = ( ... ) - 50 Hz = 8.08 Hz So the motor has 6 poles and a slip frequency of 8.08 Hz.
Description : Which statement is true concerning a split-phase induction motor? A. Motor rotation can be reversed without changing the windings or leads. B. Motor speed can be readily adjusted from zero to full ... proper wiring. D. Motor rotation can be reversed by reversing the leads on the starting winding.
Description : The speed of a squirrel-cage, multi-speed, induction motor, as used aboard ship, is varied by changing the __________. A. number of connected poles in the stator B. frequency to the motor C. excitation voltage D. resistance of the rotor circuit