DESIGN OF AC MACHINES [ ] ACTIVE LEARNING ASSIGNMENT TOPIC : DESIGN ASPECTS FOR LARGE SIZE MACHINES, HIGH VOLTAGE MACHINES, HIGH SPEED MACHINES UNIVERSITY : GUJARAT TECHNOLOGICAL UNIVERSITY COLLEGE : VADODARA INSTITUTE OF ENGINEERING DEPARTMENT : ELECTRICAL ENGINEERING [E.E.– I] SEMESTER : VII COMPILED BY : [ JESTY JOSE] [ JOBIN ABRAHAM ] [ SAGAR KALAL ] [ DENISH I. KHATRI ] GUIDED BY : ASST. PROF. NIRAV PATEL [ELECTRICAL DEPARTMENT] [ELECTRICAL DEPARTMENT] ACTIVE LEARNING ASSIGNMENT 1

 Outline  Introduction Introduction  Stator design Stator design Stator design  Rotor design Rotor design Rotor design  References References ACTIVE LEARNING ASSIGNMENT 2

 Introduction  The physical size of electrical machines is primarily determined by their torque capability.  It will be shown that the output torque is proportional to the product of the rotor volume and the shear stress. The shear stress in turn is proportional to the product of the electric and magnetic loading.  Once the approximate rotor volume has been determined, other design decisions include the rotor aspect ratio, the stator slot diameter ratio and the number of poles.  Though the torque rating is the primary factor affecting motor sizing, the motor speed rating is important in determining factors such as the maximum allowable rotor diameter (due to mechanical stress), the maximum number of poles (due to excessive iron losses) and the minimum rotor mechanical critical speed. ACTIVE LEARNING ASSIGNMENT 3

 Stator design  Proper radial air ducts are provided to ensure uniform and efficient cooling.  The stator is vacuum pressure impregnated & cured with a specially formulated epoxy resin. This ensures a sealed & homogeneous insulation system, resulting in low dielectric losses, high dielectric strength, excellent heat transfer & the elimination of hazardous internal partial discharges.  Motors are designed to stay within temperature class F (temperature limit 155).  The winding basic impulse level is kept high & windings are designed to cope with highest mechanical stresses. ACTIVE LEARNING ASSIGNMENT 4

 Rotor design  The key to a long rotor operating life is minimal vibration. This is achieved through robust construction & careful balancing.  Selecting the shaft material according to the demands of the application & the ambient conditions in which the motor is to operate.  Squirrel cages are made of copper, copper alloy or aluminum, depending upon load & customer requirements.  More care is taken during manufacture of rotor to minimize stress build-up, & the rotor bars are swaged to provide a very robust construction able to withstand heavy duties. ACTIVE LEARNING ASSIGNMENT 5

 Rotor design {cont.}  Additional stiffness is provided by fabricated rotor bars, which enable the motors to withstand long periods of heavy use.  Aluminum bars & end rings are used to ensure optimal characteristics. And, once assembled each rotor is dynamically balanced at full operating speed in accordance with the standards or mechanical vibration.  Proper radial air ducts are provided to ensure uniform & efficient cooling. ACTIVE LEARNING ASSIGNMENT 6

 Book References 1. A.K. SAWHNEY “A Course in ELECTRICAL MACHINE DESIGN”, DHANPAT RAI & Co. Pvt. Ltd., Sixth Edition, 2014 Reprint, ISBN : R.K. AGARWAL “PRINCIPLES OF ELECTRICAL MACHINE DESIGN”, S.K. KATARIA & SONS PUBLISHERS, Fourth Edition 2007, ISBN : J.B. Gupta “Theory & Performance of ELECTRICAL MACHINES”, S.K. KATARIA & SONS PUBLISHERS, Fourteenth Edition, 2013 Reprint, ISBN : M.A. Chaudhari, S.M. Chaudhari, Sachin V. Shelar “Design of AC Machines”, Tech-Max Publications, First Edition, 2016, ISBN : ACTIVE LEARNING ASSIGNMENT 7

 Website References 1. pebn/pebn009%20sizing%20of%20electrical%20machi nes.pdf pebn/pebn009%20sizing%20of%20electrical%20machi nes.pdf pebn/pebn009%20sizing%20of%20electrical%20machi nes.pdf ACTIVE LEARNING ASSIGNMENT 8

9 ANY QUESTIONS? SUGGESTIONS ARE WELCOME!