COMPUTER AIDED ANALYSIS AND DESIGN FOR ELECTRICAL ENGINEERING [ ] ACTIVE LEARNING ASSIGNMENT: TOPIC : VENTILATION SCHEMES IN ROTATING MACHINES. UNIVERSITY : GUJARAT TECHNOLOGICAL UNIVERSITY. COLLEGE : VADODARA INSTITUTE OF ENGINEERING. DEPARTMENT : ELECTRICAL ENGINEERING [E.E.– I]. SEMESTER : VI. PREPERED BY : [ MEET K. JANI ] [ BHARGAV M. JAYSWAL ] [ JESTY JOSE ] [ JOBIN ABRAHAM ] GUIDED BY :ASST. PROF. ABHISHEKH PATEL. [ELECTRICAL DEPARTMENT] [ELECTRICAL DEPARTMENT] ACTIVE LEARNING ASSIGNMENT 1

 Contents:  Introduction Introduction  Radial ventilation system Radial ventilation system Radial ventilation system  Axial ventilation system Axial ventilation system Axial ventilation system  Forced ventilation system Forced ventilation system Forced ventilation system  Induced ventilation Induced ventilation Induced ventilation  References References ACTIVE LEARNING ASSIGNMENT 2

 Introduction  In rotating machines heat transfer is much better (i.e. due to its rotatory motion) as the rotating component enhances cooling medium, pressure and discharge.  Various ventilation or cooling methods commonly used for rotating electrical machines are classified as follows:  Radial ventilation system,  Axial ventilation system,  Combined ventilation system,  Forced ventilation system, and  Induced ventilation system.  The method employed for a particular machine depends on size of machine and on its types. ACTIVE LEARNING ASSIGNMENT 3

 Radial ventilation system  This system is mainly used for machines of medium and large output.  The core is divided into a number of separate stacks each of 6 cm to 10 cm thickness.  Between any two core stacks a radial ventilating duct of 1 cm width is provided.  In radial ventilation, the rotation of rotor causes natural centrifugal movement of the air, augmented as required by rotor fans. This air circulation takes away heat generated in the windings and core, heat is dissipated into the frame from there it is radiated. ACTIVE LEARNING ASSIGNMENT 4

 Advantages: 1. Minimum energy losses for ventilation 2. Sufficiently uniform temperature rise of machines.  Disadvantages: 1. An appreciable portion of armature length is occupied by ventilation duct, so net core length is reduced. 2. The heat dissipation is less than in other systems of ventilation. ACTIVE LEARNING ASSIGNMENT 5  Radial ventilation system {cont.}

 Axial ventilation system  It is commonly used for high speed machines of small and medium output.  When applied in induction machine with axis ducts only on the rotor. Such a system with axial ducts on the rotor is called simple axial.  If the axial ducts are provided on the stator and rotor of machine system is known as double axial system. ACTIVE LEARNING ASSIGNMENT 6

 Axial ventilation system {cont.}  Advantage:  The length of the core increases as there is no radial ventilation ducts.  Disadvantage:  The heat transfer is not uniform. ACTIVE LEARNING ASSIGNMENT 7

 Combined (Radial and Axial) ventilation system  This system employs the main advantages of both the earlier methods.  It is used for cooling of large electrical machines. ACTIVE LEARNING ASSIGNMENT 8

 Combined (Radial and Axial) ventilation system {cont.}  In this, the air is drawn in at one end of the machine.  Then the air is circulated through the ventilation ducts and expelled into ambient atmosphere by the rotor mounted fan.  In the case of totally enclosed machines as they have no air connection with the outside atmosphere, this method is employed with addition of external and internal fans.  The external fan blows air over the carcass through a space between the main housing and thin cover plate, whereas the internal fan produces the internal air circulation. ACTIVE LEARNING ASSIGNMENT 9

 Forced ventilation system  Large machines such as modern turbo-generators cannot be cooled by any of the above methods.  Large machines require forced ventilation due to their compact design, in other words large amount of heat is dissipated from a small area. ACTIVE LEARNING ASSIGNMENT 10

 Forced ventilation system {cont.}  The rate of heat dissipation by forced cooling depends on the following:  The volume of gas to be passed through the machine.  The surface exposed to cooling.  Difference in temperature between the cooling air and the surface to be cooled.  Large machines requires tons of cooling air which is forced through ventilating ducts at high velocities.  All turbo-generators are cooled by forced ventilation.  They are totally enclosed, using a closed circuit system for circulating the air as shown. ACTIVE LEARNING ASSIGNMENT 11

 Induced ventilation  There are two types  Cooling of machine with external fan Cooling of machine with external fan Cooling of machine with external fan  Cooling of machine with internal fan Cooling of machine with internal fan Cooling of machine with internal fan ACTIVE LEARNING ASSIGNMENT 12

 Cooling of machine with external fan  In this method a cooling fans are installed outside the machine.  The external fan are used to provide cooling to the machine by extracting the heat or hot air from the machine and throw the air outside.  The fans are operated after the machine gets heated up. ACTIVE LEARNING ASSIGNMENT 13

 Cooling of machine with internal fan  In this method a cooling fans are installed inside the machine.  The fans are operated with the machine so it provides cooling continuously with the operation of machine.  This method provide a better cooling as compared to external cooling. ACTIVE LEARNING ASSIGNMENT 14

 Conclusions  Radial ventilation system is used for machines of medium and large output.  Axial ventilation system is used for high speed machines of small and medium output.  Combined ventilation system is used for cooling of large electrical machines.  All turbo-generators are cooled by forced ventilation. ACTIVE LEARNING ASSIGNMENT 15

 References 1. Computer-Aided Design of Electrical Machines, e-book [ K.M. Vishnu Murthy ] {BS Publications} (2008). 2. Computer Aided Design of Electrical Machines, First Edition [ V.K. Maurya, Ritu Raj Jalan, Shasya Shukla ] {S.K. KATARIA & SONS PUBLISHERS} (2014). 3. AN INTRODUCTION TO THE Finite Element Method, Third Edition, 23 rd Reprint 2015 [ J.N. Reddy ] {McGraw Hill Education (INDIA) Pvt. Ltd.} (2015). ACTIVE LEARNING ASSIGNMENT 16

ANY QUESTIONS? ANY QUESTIONS? ACTIVE LEARNING ASSIGNMENT 17