Machine II: PUT Question Paper- RTU

Department of Electrical Engineering Pre-University Test : 08/05/2017 4EE10A: Electrical Machines II Attempt all questions. Internal options are given in each question. All questions have been asked in previous year RTU Papers 1 a) Derive the basic emf equation for an induced emf per phase for full pitch, concentrated type winding. 2014 8 b) An alternator runs at 250 rpm and generates an emf of 50 Hz. The winding distribution factor Kd is 0.9597 and Pitch factor Kp (or coil span factor Kc) is 1. All the conductors of each phase are in series and flux per pole is 30 milliweber, which is sinusoidally distributed. If the winding is star connected, determine the value of induced emf available across terminal. 2014 8 OR 1 a) Explain the concept of rotating magnetic field. 2014 8 b) Explain the different ways to eliminate the harmonics effect from generated voltage 2014 8 2 a) Draw the Torque-Slip Characteristics of 3-Phase Induction motor and explain it. Find condition of maximum torque. Show the effect of rotor resistance on torque-slip characteristics. 2015 8 b) A 10-hp, 4 pole, 50 Hz, 3 phase Induction motor runs at 1450 rpm at full load. The stator copper loss is 231 Watt and rotational loss is 343 Watt. Determine i) Shaft torque, ii) Mechanical power developed, iii) Air gap power, iv) Rotor copper loss and v) Motor efficiency. 2015 8 OR 2 a) Explain the equivalent circuit of Induction motor. Draw basic equivalent circuit and approximate equivalent circuit. 2014 8 b) A 4-pole, 3 phase star connected induction motor is supplied from a 50 Hz supply. Determine its synchronous speed. On full load, its speed is observed to be 1410 rpm. Calculate its full load slip. When the full load slip becomes 4%, calculate its full load speed. 2014 8 3 a) Draw equivalent circuit of single phase Induction motor and explain its working principle. 2015 8 b) Explain the working of Universal Motor 2015 8 OR 3 a) Explain the double revolving field theory of single phase Induction Motor. 2015 8 b) Describe the working of stepper motor with its diagram 2015 8 4 a) Explain Zero Power Factor (ZPF Method) characteristics and concept of Potier triangle in Synchronous Generator. 2013 8 b) Explain Synchronization and Parallel operation in Synchronous Generator. 2013 8 OR 4 a) Draw Phasor diagram of lagging power factor of Synchronous Generator. A 3 phase, 10 kVA, 400 Volts, 50 Hz, star connected alternator supplies the rated load at 0.8 power factor lagging. If armature resistance is 0.5 Ohm and synchronous reactance is 10 Ohm, find the torque angle and voltage regulation. 2015 8 b) Give the advantage for providing armature winding on stator circuit rather than rotor circuit. Explain the working principle of 2- Pole Synchronous Generator. 2014 8 5 a) Describe the power factor control of synchronous motor under: i)                    Under Excitation ii)                   Normal Excitation iii)                 Over Excitation Draw V curve and inverted V curve. 2014 8 b) Explain the principle of operation of a 3 phase Synchronous Motor. Why synchronous motor is not self starting? 2014 8 OR 5 a) Explain Synchronous Induction Motor (Slip ring starting method of Synchronous Motor) 2013 8 b) What is hunting of synchronous machines and how it can be eliminated? 2015 8