Previous year Questions -ELECTRICAL MACHINES -II

Previous year Questions

Electrical Machines –II

JNTUH R18 B.Tech II  EEE

Short answer Questions :

• List any two differences between cage rotor and wound rotor. [2]
• Explain the concept of RMF. [3]
• Draw torque – slip characteristic of three phase IM. [2]
• What is cogging? Explain? [3]
• Why two reactances are required for the analysis of Salient pole alternator? [2]
• List the differences between distributed and concentrated windings. [3]
• What is synchronizing torque? [2]
• What is Synchronous induction motor? Explain? [3]
• Why single phase IM is not self starting? [2]
• List Applications of shaded pole motor.
• What is rotating magnetic field of a three phase induction motor. [2]
• Define slip of an induction motor. Write the equation for the same. [3]
•  What is cogging of an induction motor? [2]
•  List three different speed control methods of a three phase induction motor. [3]
•  List any two advantages of rotating magnetic field in Synchronous Generators. [2]
•  List any three differences between smooth Cylindrical and Salient pole types of Alternator. [3]
• Why a 3-phase synchronous motor always runs at synchronous speed? [2]
•  List any three conditions to be satisfied for parallel operation of alternators. [3]
• Classify different types of single phase induction motors. [2]
•  Explain Double revolving field theory of Single phase Induction motor. [3]
•  What is slip and slip speed of an Induction motor? [2]
•  Give the applications of 3-phase induction motor. [3]
•  What is crawling in Three-phase Induction motor? [2]
•  What is the principle of V/f speed control in Induction motor? [3]
•  What is pitch factor? [2]
•  Draw the load characteristics of an alternator. [3]
• What is Synchronous reactance of an alternator? [2]
•  Write short note on Synchronous induction motor. [3]
• State the disadvantages of single phase Induction motor. [2]
• Give the applications of shaded pole induction motor. [3]
•  Write the merits and demerits of slip-ring induction motor. [2]
• Write the effects of crawling and cogging on the performance of induction motor. [3]
• What is the procedure to conduct the blocked rotor test on 3-ϕ induction motor? [2]
• Why starting methods are needed for 3-ϕ induction motor
• What is the effect of skewing the rotor slots of an induction motor? [2]
• Draw the speed-torque characteristics of a deep-bar double cage induction motor. [3]
• What are the limitations of speed control by conventional methods? [2]
• What will be the effect on torque developed by an induction motor if applied voltage is reduced to half with frequency unchanged?
• Define slip. And explain necessity of slip in an induction motor. [2]
• Define frequency of rotor current and its condition during starting and synchronous speed. [3]
• What information can be obtained from circle diagram of 3-ϕ Induction Motor? [2]
• What is the necessity of speed control of a three phase induction motor?
• Derive the condition for maximum torque at the time of starting in a 3-ϕ I.M. [2]
•  Derive the condition for maximum torque under running conditions in a 3-ϕ I.M. [3]
• Explain the working principle of Induction generator. [2]
• Explain the speed control of 3-ɸ IM using cascade connection