Electrical Engineering interview questions and answers - part 2

Part 1   Part 2   Part 3   Part 4   Part 5   Part 6 9. Explain advantages of storage batteries Few advantages of storage batteries are mentioned below: • Most efficient form of storing energy portably. • Stored energy is available immediately because there is no lag of time for delivering the stored energy. • Reliable source for supply of energy. • The energy can be drawn at a fairly constant rate. 10. What are the different methods for the starting of a synchronous motor. Starting methods: Synchronous motor can be started by the following two methods: • By means of an auxiliary motor: The rotor of a synchronous motor is rotated by auxiliary motor. Then rotor poles are excited due to which the rotor field is locked with the stator-revolving field and continuous rotation is obtained. • By providing damper winding: Here, bar conductors are embedded in the outer periphery of the rotor poles and are short-circuited with the short-circuiting rings at both sides. The machine is started as a squirrel cage induction motor first. When it picks up speed, excitation is given to the rotor and the rotor starts rotating continuously as the rotor field is locked with stator revolving field. 11. Name the types of motors used in vacuum cleaners, phonographic appliances, vending machines, refrigerators, rolling mills, lathes, power factor improvement and cranes. Following motors are used: - • Vacuum cleaners- Universal motor. • Phonographic appliances – Hysteresis motor. • Vending machines – Shaded pole motor. • Refrigerators – Capacitor split phase motors. • Rolling mills – Cumulative motors. • Lathes – DC shunt motors. • Power factor improvement – Synchronous motors. 12. State Thevenin’s Theorem: According to thevenin’s theorem, the current flowing through a load resistance Connected across any two terminals of a linear active bilateral network is the ratio open circuit voltage (i.e. the voltage across the two terminals when RL is removed) and sum of load resistance and internal resistance of the network. It is given by Voc / (Ri + RL). 13. State Norton’s Theorem The Norton’s theorem explains the fact that there are two terminals and they are as follows: • One is terminal active network containing voltage sources • Another is the resistance that is viewed from the output terminals. The output terminals are equivalent to the constant source of current and it allows giving the parallel resistance. The Norton’s theorem also explains about the constant current that is equal to the current of the short circuit placed across the terminals. The parallel resistance of the network can be viewed from the open circuit terminals when all the voltage and current sources are removed and replaced by the internal resistance. 14. State Maximum power transfer theorem The Maximum power transfer theorem explains about the load that a resistance will extract from the network. This includes the maximum power from the network and in this case the load resistance is being is equal to the resistance of the network and it also allows the resistance to be equal to the resistance of the network. This resistance can be viewed by the output terminals and the energy sources can be removed by leaving the internal resistance behind. Part 1   Part 2   Part 3   Part 4   Part 5   Part 6 Write your comment - Share Knowledge and Experience Discussion Board eee principle of transformer is mutual inductance. one morething if any question in transformer section containg the word battery means definetly the answer is zero MAHA 08-30-2016 04:32 AM machine nice..give more useful intervie qurstion over machine.. jyotirmoy sahoo 01-8-2016 04:44 AM principles I want all the principles of electrical devices such as transformer,induction motor/generator,synchronous machine/generator,etc....... Anyone please help me by giving above details THANK YOU IN ADVANCE snega priya 10-20-2015 11:10 AM DC series motor When the motor is connected across the supply without load,it draws small current from supply main through the series field and armature, the speed tend to increase so that back emf may approach the applied voltage in magnitude.the increase in back emf weakness the armature current and hence the field current .this causes again in increase in speed and back emf .thus field continue to weaken and speed continue to increase until the armature gets damage bikram 03-17-2015 12:12 PM eee why capacitors use in LT panel kiran 01-21-2015 02:04 AM EEE What happened in the D.C series motor starting without load?if it is started how much times it can be run? JEYAKUMAR.M 12-28-2014 10:47 PM EEE What happened while connecting the AMMETER in parallel and VOLT METER in the closed circuit? JEYAKUMAR 12-28-2014 10:43 PM EEE WHAT IS MEANED BY PREVENTIVE MAINTAIENCE sreejith 11-6-2014 10:28 AM interview Q & A Electrical eng.... Very use full web site for jobless student thank you for making manthan 09-17-2014 11:48 PM comment this can be answer by 2nd year student give some hard questions Anu 10-9-2013 12:45 PM