COMPUTER AIDED ANALYSIS AND DESIGN FOR ELECTRICAL ENGINEERING. ventilation schemes in rotating machines. PREPARED BY: JOBIN ABRAHAM.

1. COMPUTER AIDED ANALYSIS AND
DESIGN FOR ELECTRICAL
ENGINEERING [2160911]
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 :
130800109025 [ MEET K. JANI ]
130800109026 [ BHARGAV M. JAYSWAL ]
130800109027 [ JESTY JOSE ]
130800109028 [ JOBIN ABRAHAM ]
GUIDED BY :ASST. PROF. ABHISHEKH PATEL.
[ELECTRICAL DEPARTMENT]
ACTIVE LEARNING ASSIGNMENT
1

2.  Contents:
 Introduction
 Radial ventilation system
 Axial ventilation system
 Forced ventilation system
 Induced ventilation
 References
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3.  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.
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4.  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.
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5.  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.
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 Radial ventilation system {cont.}

6.  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.
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7.  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.
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8.  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.
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9.  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.
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10.  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.
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11.  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.
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12.  Induced ventilation
 There are two types
 Cooling of machine with external fan
 Cooling of machine with internal fan
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13.  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.
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14.  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.
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15.  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.
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16.  References
1. Computer-Aided Design of Electrical Machines, e-book
[ K.M. Vishnu Murthy ] {BS Publications} (2008) <ISBN
: 978-81-7800-146-3>.
2. Computer Aided Design of Electrical Machines, First
Edition [ V.K. Maurya, Ritu Raj Jalan, Shasya Shukla
] {S.K. KATARIA & SONS PUBLISHERS} (2014) <ISBN :
978-93-5014-525-8>.
3. AN INTRODUCTION TO THE Finite Element Method,
Third Edition, 23rd Reprint 2015 [ J.N. Reddy ]
{McGraw Hill Education (INDIA) Pvt. Ltd.} (2015)
<ISBN : 978-0-07-060741-5>.
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17. ANY QUESTIONS?
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