Description : Why Induction motor is called rotating transformer?
Last Answer : Transformer has two sides: primary & secondary. Transformer transforms energy from primary to secondary by induction. Similarly, Induction motor has primary (stator) & secondary (rotor). Voltage is ... magnitude i.e. the process of induction Thus induction motor treated as a rotating transformer.
Description : 9 Which loss is not common between a transformer and rotating machines? A. Eddy current loss B. Copper loss C. Windage loss D. Hysteresis loss
Last Answer : A. Eddy current loss
Description : 17. Which type of loss is not common to transformer and rotating machines? A. Eddy current loss B. Copper loss C. Hysteresis loss D. Windage loss
Last Answer : D. Windage loss
Description : why induction motor is called rotating transformer?
Last Answer : Induction motor works on same principal as transformers work ie faradays law of electromagnetic induction. ie IM called as rotating transformer
Description : what is mean by rotating transformer ?
Last Answer : Induction motor is a rotating transformer
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
Last Answer : Answer: D
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
Last Answer : Answer: A
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.
Last Answer : Answer: B
Description : What is the main function in the use of a capacitor for starting a single phase motor? A. Reduce radio interference B. Split the phase to establish a rotating magnetic field C. Reduce the phase angle D. Prolong the life of the starting contacts
Description : When two AC generators are being paralleled, the breaker should be closed with the synchroscope pointer rotating in the ____________. A. 'slow' direction, just before the 12 o'clock position B. 'fast' ... just before the 12 o'clock position D. 'slow' direction, just after the 12 o'clock position
Last Answer : Answer: C
Description : If the pointer of the synchroscope is rotating in the slow direction when you are preparing to parallel two alternators, the _____________. A. incoming machine is turning faster than the load alternator B ... alternator is ready to split D. incoming machine is beginning to pick up some of the load
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 : 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 : 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 rotor of a synchronous motor operates in synchronism with the rotating field because ______________. A. of the amortisseur windings B. the rotor is magnetically locked into step with the ... field strength varies directly with rotor slip D. the stator flux rotates in the opposite direction
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 : The direction of rotation of an induction motor is ________. A. opposite the rotating field direction B. the same as the direction of the rotating field C. determined by the number of poles D. determined by the staggering of the brushes
Description : What will be the phase angle relationship of a six-pole, three-phase, rotating field generator? A. 60° B. 120° C. 180° D. 360°
Description : A synchronous motor maintains synchronism with the rotating field because _____________. A. field strength varies directly with rotor slip B. DC current applied to the rotor coils causes the rotor ... the flux created by the excitation current D. the stator flux rotates in the opposite direction
Description : Which of the following statements is true concerning all three-phase alternators? A. Each has three separate but identical armature windings acted on by one system of rotating magnets. B. Each has one ... The three phases always provide power to the load through three sets of slip rings and brushes.
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 : 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 : In an induction motor, rotor currents are circulated in the rotor by _____________. A. slip rings and brushes B. an armature and brushes C. inductive reaction of the rotating stator field D. external variable resistors
Description : On some diesel-electric ships, the DC propulsion motor will only attain half speed when the generator fields are fully excited. Speeds above this are obtained by _____________. A. rotating brush ... B. raising the generator engine speed C. lowering the generator engine speed D. decreasing excitation
Description : What is the direction of rotation of rotor with respect to the rotating magnetic field?
Last Answer : Answer: Rotating Magnetic Field is set up when 3 phase ac supply is provided to the stator windings of the induction motor. Rotating Magnetic Field rotates at synchronous speed. Rotor rotates in the direction of the rotating magnetic field
Description : Name power loses in rotating electrical machines.
Last Answer : A: Power losess in rotating electrical machines are Copper losses, core losses, mechanical losses and stray losses.
Description : Will The Alternators Have Rotating Armature System Or Stationary Armature System?
Last Answer : Generally in alternators, the armature is stationary and the field rotates. Small low-voltage alternators often have a rotating armature and a stationary field winding. But in large alternators rotating armature field type is used.
Description : What Are The Advantages Of Stationary Armature And Rotating Field System?
Last Answer : The stationary armature coils can be insulated easily. Higher peripheral speed can be achieved in the rotor. Cooling of the winding is more efficient. Only two slip rings are required to give DC ... Output current can be easily supplied to the load circuit. Slip-rings and brushes are not necessary.
Description : Why almost all large size Synchronous machines are constructed with rotating field system type?
Last Answer : The following are the principle advantages of the rotating field system type construction of Synchronous machines: 1. Small size 2. low centrifugal forces 3. easy to insulate field winding 4 ... better ventilation 7. higher speed 8. reduce sparking problems 9. higher capacity
Description : What is the classification of duty of rotating electrical machines?
Last Answer : S1 - Continuous operation at rated load (MCR) in 40 °C S2 - Short time operation (STR) for 5 minute or 15 minutes or 30 minutes. S3 - Intermittent periodic operation (resting and loading e.g. ... As for S3 but with starting S5 - As for S3 with electric braking S6 - Continuous cyclic operation.
Description : What is the minimum recommended absorption coefficient value for AC and DC rotating machines?
Last Answer : Tips: a. IR value decreases some what with an increase I applied voltage. However for machines in good condition substantially the same IR is obtained for any test voltage ... a value which after correction for temperature, may be compared with the recommended minimum value of IR.
Description : What are the minimum recommended PI values for AC and DC rotating machines?
Last Answer : Following minimum recommended PI values criteria is to be followed. a. 1.5 for class – A insulation. b. 2.0 for class – B insulation. c. 2.5 for class – F insulation.
Description : What are the advantages of rotating field system?
Last Answer : a. For rotating field alternators only two slip rings and brush gear assembly are required irrespective of number of phases. b. The DC excitation voltage is low and it is very easy to insulate ... mechanical stress set as a result of short circuit current and the high centrifugal brought into play.
Description : In a d.c. machine, the armature mmf is (A) stationary w.r.t. armature. (B) rotating w.r.t. field. (C) stationary w.r.t. field. (D) rotating w.r.t. brushes.
Last Answer : (C) stationary w.r.t. field.
Description : In conversion of 3-phase to 2-phase supply with T connection, the transformation ratio of the teaser will be__ times to that of main transformer: a) 1.732 b) 1.15 c) 0.866 d) Unity
Last Answer : Ans: C
Description : The harmonic currents in a power transformer does not cause increase in: a) Secondary voltage b) Core loss c) Copper loss d) Magnetic interference with protective relays
Last Answer : Ans: A
Description : An auto transformer is preferred over an ordinary two winding transformer due to: a) Safety of operation b) Availability of taps on secondary c) Copper savings d) All the above
Description : In a transformer, with closed magnetic coupling between primary and secondary __ will improve: a) Efficiency b) All day efficiency c) Regulation d) None of the above
Description : Booster transformer should never: a) Have fuse in the HV winding b) Be left open circuited c) Be left closed circuited d) None of the above
Last Answer : Ans: B
Description : The rating of the Transformer __ when the supply frequency is increased: a) Remains unchanged b) Increases c) Decreases d) None of the above
Description : Stones are provided in the substation to: a) To avoid fire accident by draining oil from transformer if leaks b) To avoid growing of weeds and plants c) To provide insulation d) All the above
Last Answer : Ans: D
Description : A transformer has negative voltage regulation when its load power factor is- (a) Zero (b) Unity (c) Leading (d) Lagging
Description : The electrical schematic illustrated in figure A, depicts a/an _____________. EL-0059 A. autotransformer B. Delta Wye transformer C. primary EMF generator D. potential transformer
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 : The symbol shown as figure 'A' represents a/an ____________. EL-0059 A. transformer B. coil C. shunt field D. inductor
Description : The diagram shown in the illustration represents a/an _____________. EL-0082 A. stepup transformer B. magnetic amplifier C. autotransformer D. Scott-connected transformer
Description : In electric circuit schematics, a transformer is represented by which of the symbols shown in the illustration? EL-0059 A. A B. B C. C D. D
Description : Which of the following statements identifies the difference between the primary windings and the secondary windings of a 2:1 stepdown transformer? A. The secondary windings have twice as much resistance ... primary windings. D. The secondary windings have half as many turns as the primary windings.
Description : An open coil in a transformer will be indicated by which of the listed conditions? A. 'zero' resistance accompanied by high inductance B. no resistance accompanied by stray inductance C. infinite resistance in addition to no inductance D. infinite resistance in addition to normal inductance
Description : A load with an impedance of 440 ohms is connected across the secondary of the transformer illustrated. If the input voltage is 110 VAC and the step-up ratio is 10 to 1, what will be the primary current? EL-0055 A. 2.5 amps B. 25 amps C. 250 amps D. current cannot be determined with information given