An auxiliary phase winding is used in a single-phase fractional horsepower motor to A. decrease flux density. B. reverse motor rotation. C. increase motor speed. 11.B. How is a rotating magnetic field produced during starting in a split-phase motor? A. A low resistance coil is placed around a portion of each pole. B. An auxiliary winding is made

An auxiliary phase winding is used in a single-phase fractional horsepower motor to A. decrease flux density. B. reverse motor rotation. C. increase motor speed. 11.B. How is a rotating magnetic field produced during starting in a split-phase motor? A. A low resistance coil is placed around a portion of each pole. B. An auxiliary winding is made

Electric Motor Control

10th Edition

ISBN:9781133702818

Author:Herman

Publisher:Herman

Chapter51: Electric And Electronic Braking

Section: Chapter Questions

Problem 2SQ: Differentiate between the AC and DC magnetic fields applied to an induction motor stator.

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DEGREE: ELECTRICAL ENGINEERING SUBJECT/COURSE: AC MACHINES Answer the following questions (A, B and C) depending on the topic. 1. ALTERNATORS A. Why is it necessary to maintain the speed of an alternator at all times and how do they control the speed of an alternator when in operation? B. Distinguish between half-coiled and full-coiled armature windings in alternators. C. Why are fractional pitch windings generally used in alternators?
Q5) Identify the machine where the Rotating magnetic field is produced. a. Three Phase Induction Motor b. DC Motor c. DC Generator d. Transformer
A) Although the magnetic field for each phase of a 3-phase induction motor is merely switching back and forth between north and south poles, the resultant magnetic influence from all phases sets up a rotating magnetic field to cut the rotor conductors. a) true b) false B) In a two-pole stator winding of a 3-phase motor, how many revolutions does the rotating tr) magnetic field make in one cycle of the electrical current? a) one b) 60 c) 3600 d) none of the above
The stator of a three-phase, 60-Hz, 8 pole synchronous generator has 48 slots. Determine (a) the speed of the rotor, (b) the number of coils in a phase group, (c) the slot pitch, and (d) the coil pitch. Sketch the winding arrangement for two phase groups.
Calculate the synchronizing torque for one mechanical degree of phase displacement in a 6,019-kVA, 50-Hz, alternator when running at 1,500 r.p.m with a generated e.m.f. of 10,000 volt. The machine has a synchronous impedance of 25%.
A 6-pole, dc machine has a double layer, lap winding in 63 slots. The coils in the machine have one turn each. There are 189 commutator bars. The flux per pole is 0.082 Wb. The rotor speed is 700 rev/min. a. Find the number of coils per slot. b. Find the number of conductors per slot. c. Is full-pitch winding possible? Why? d. Find the number for the bottom-layer conductor of coil 1. e. We can decide to use equalizers on this machine. Why? f. It is possible to use 21 equalizers on this machine. Why? h. Find the commutator bar(s) to be connected with the commutator bar 1 to an equalizer. i. Find the commutator bar(s) that must be connected to equalizer number 5 if 21 equalizers are used and commutator bar 1 is connected to equalizer number 1. g. Find the dc voltage that is generated in this machine.
11/ Name the type of three-phase induction motor, which provides low starting torque. a. Squirrel cage rotor b. Single phase induction motor c. DC motor d. slip ring rotor
A 4 pole dc generator runs at 750 rpm and generates an emf of 240 V. The armature is wave wound and has 792 conductors. If the total flux from each pole is 0.0145 Wb, If leakage coefficient is given as the ratio of the total flux/pole to the working flux per pole, find its value.
Q.36 Name three factors that determine the torque produced by an induction motor. Select one or more: A. THE ARRANGEMENT OF THE STATOR WINDINGS B. THE PHASE ANGLE DIFFERENCE BETWEEN ROTOR AND STATOR FLUX C. THE SPEED OF THE CUTTING ACTION D. THE STRENGTH OF THE MAGNETIC FIELD OF THE STATOR E. THE NUMBER OF TURNS OF WIRE IN THE ROTOR F. THE STRENGTH OF THE MAGNETIC FIELD OF THE ROTOR
A 6-pole, dc machine has a double layer, lap winding in 63 slots. The coils in the machine have one turn each. There are 189 commutator bars. The flux per pole is 0.082 Wb. The rotor speed is 700 rev/min. A. Find the number of coils per slot. B. Find the number of conductors per slot. C. Is full-pitch winding possible? Why? D. Find the number for the bottom-layer conductor of coil 1. We can decide to use equalizers on this machine. Why? E. It is possible to use 21 equalizers on this machine. Why?
A 20-pole, Y-connected, three-phase, 400-Hz alternator has 3 coils per phase group. Each coil has 2 turns and the flux per pole is 23 mWb. The coils are connected in two parallel groups. Determine (a) the rotor speed, (b) the number of slots in the armature, (c) the winding factor, (d) the per-phase voltage, and (e) the line voltage.
3.An induction motor has a rotor resistance and reactance at standstill of 0.1 ohm and 3.5 ohm respectively. At standstill the voltage induced to the rotor is 60volts per phase. If the slip is 5%, determine the rotor current