A- Discuss why rotor slots of three-phase induction motor are skewed? B- Draw torque-speed characteristics of three-phase induction motor assigning: locked rotor torque, pull up torque, breakdown torque, full load torque and accelerating torque? C- Explain briefly the soft starting of three-phase induction motor?

F-a). Single-phase repulsion motors have......... . a) excellent starting torque b) excellent running torque c) unstable speed characteristics d) all of the above F-b). Which type of repulsion motor runs quieter? a) repulsion b) repulsion-start, induction-run c) repulsion-induction d) they are all the same F-c. Single-phase repulsion-induction motors have........ . a) high starting torque b) good speed regulation c) both "a" and "b" d) neither "a" nor "b"

8. Homework: III. IV. V. What is the effect of load on the efficiency of an induction motor? Explain the term air-gap power or power developed in the rotor and shaft power. How these terms are related to each other? Derive an expression for the rotor copper loss in terms of slip and input to the rotor? What are the various losses in an induction motor? On what factors do they depend? List the different types of stray load losses in an induction motor.

A 110-V, 1-phase, 4-pole, 60-Hz induction motor has the following circuit constants: R1 = R2’ = 1.6 ohm,X1 = X2’ = 1.8 ohm, Xm = 60 ohm; core loss is 16 W and friction and windage loss is 12 W. Determine theefficiency of the motor at 0.04 slip by using (a) the exact equivalent circuit and (b) the approximateequivalent circuit

A wound rotor, induction motor has a rotor resistance of 0.6 ohms per phase and a rotor leakage reactance of 8 ohms.a)What is the operating speed (rpm) of this 2-pole induction motor fed from a 50Hz supply if the slip is 5%?b)If maximum torque occurs when R2 = sX2, what is the slip at maximum torque?c)What resistance must be added to the rotor circuit to give maximum startingtorque?

Does a DC motor have to be turning in order for it to develop torque? a) yes b) no Most DC motor consist of many turns per armature loop as well as many evenly distributed loops per al mature. a) true b) false Brushes a DC motor. a) are part of the electrical circuit in b) provide a sliding electrical contact to the commutator of c) are made of a material which is softer than the commutator segments of d) all of the above

QUESTION 2 a) Draw the equivalent circuit and torque-speed characteristic curve for a series DC motor. b) Briefly explain the induced torque occurs in a series DC motor. e) A 20-hp 240-V 76-A 900 rimin series motor has a field winding of 33 turns per pole. Its armature resistance is 0.09 2, and its field resistance is 0.06 2. The magnetization curve expressed in terms of magnetomotive force versus Ex at 900 rimin is given by the following table: Table Q2 c): The magnetomotive force table for a de motor taken at 900r'min E. V 95 150 188 212 229 243 F.A tuus 1000 1500 2000 2500 500 3000 If the motor running at 33 percent of the full-koad armature current, determine: ) The motor's power converted from electrical to mechanical form, Prene i) The motor's torque, Tnit ii) The motor's speed, n

I need an expert's solution to the following questions in a simple manner, without too .much explanation 1. Discuss the ratios of no load current, and starting current of three phase induction motor to its rated value? 2. Explain the applications of three phase wound rotor I.M? 3. Why is the starting torque increased by providing external resistance on the wound rotor type induction motor? 4. Why does an induction motor always works on lagging P.F? 5. What are the advantages of adding an external resistance to the rotor circuit of three-phase wound rotor induction motor?

50. A) The rotor conductors of the 3-phase double-squirrel-cage induction motor are used during the starting cycle of the motor. a) inner b) outer B) How does the starting torque of a 3-phase double-squirrel-cage induction motor compare with the standard 3-phase squirrel-cage motor? a) starting torque is better in the double-squirrel-cage motor b) starting torque is better in the standard squirrel-cage motor c) they are about the same C) How does the starting current of a 3-phase double-squirrel-cage induction motor compare with the standard squirrel-cage induction motor? a) starting current is lower in the double-squirrel-cage motor b) starting current is lower in the standard squirrel-cage motor c) they are about the same

6- In a stepper motor, how is the speed of rotation determined? a) By the current supplied to the motor. b) By the magnitude of the voltage applied. c) By the load applied to the motor. d) By the frequency of the waveforms used. 7- A transformer core is laminated to a) reduce hysteresis loss b) reduce eddy current losses c) reduce copper losses d) reduce all above losses 8- An induction motor with 580 r.p.m. speed at 60 Hz will have a) 8 poles b) 6 poles c) 4 poles d) 2 poles 9- If any two phases for an induction motor are interchanged a) the motor will run in reverse direction b) the motor will run at reduced speed c) the motor will not run d) the motor will burn 10- No-Load speed of which of the following motor will be highest? a) Shunt motor b) Series motor c) Short-Shunt compound motor d) Long-Shunt compound motor