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This document deals with basics of electrical machine design. It will also give you detailed knowledge of MAGNETIC CIRCUIT AND COOLING OF ELECTRICAL MACHINE.
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EE 1403 DESIGN OF ELECTRICAL APPARATUS
BY
V.BALAJI, B.E. M.Tech, (Ph.D), MIEE, MISTE, MIAENG.Asst.ProfessorEEEDhanalakshmi College of Engg
1. MAGNETIC CIRCUITS AND COOLING OF ELECTICAL MACHINES
� Concept of magnetic circuit – MMF calculation for various types of electrical machines – real and apparent flux density of rotating machines –leakage reactance calculation for transformers, induction and synchronous machine - thermal rating: continuous, short time and intermittent short time rating of electrical machines-direct and indirect cooling methods – cooling of turbo alternators.
i. To study mmf calculation and thermal rating of various types of electrical machines.
ii. To design armature and field systems for D.C.machines.
iii. To design core, yoke, windings and cooling systems of transformers.
iv. To design stator and rotor of induction machines.
v. To design stator and rotor of synchronous machines and study their thermal
SYALLBUS
D.C. MACHINES
Constructional details – output equation –main dimensions - choice of specificloadings – choice of number of poles –armature design – design of field polesand field coil – design of commutator and brushes – losses and efficiencycalculations.
TRANSFORMERS Constructional details of core and shell type transformers – output rating of single phase and three phase transformers – optimum design of transformers – design of core, yoke z and windings for core and shell type transformers – equivalent circuit parameter from designed data – losses and efficiency calculations – design of tank and cooling tubes of transformers.
THREE PHASE INDUCTION MOTORS Constructional details of squirrel cage and slip ring motors – output equation –main dimensions – choice of specific loadings –design of stator – design of squirrel cage and slip ring rotor – equivalent circuit parameters from designed data – losses and efficiency calculations.
SYNCHRONOUS MACHINES 9Constructional details of cylindrical pole and salient pole alternators – output equation – choice of specific loadings –main dimensions – short circuit ratio –design of stator and rotor of cylindrical pole and salient pole machines - design of field coil - performance calculation from designed data - introduction to computer aided design.
TEXT BOOKS1. A.K. Sawhney, ‘A Course in Electrical Machine Design’, Dhanpat Rai and Sons, New Delhi, 1984.2. S.K. Sen, ‘Principles of Electrical Machine Design with Computer Programmes’,Oxford and IBH Publishing Co.Pvt Ltd., New Delhi, 1987.
REFERENCE BOOKS1. R.K. Agarwal, ‘Principles of Electrical Machine Design’, S.K.Kataria and Sons,Delhi, 2002.2. V.N. Mittle and A. Mittle, ‘Design of Electrical Machines’, Standard Publicationsand Distributors, Delhi, 2002.
Unit Unit --11
MAGNETIC CIRCUITS AND COOLING OF ELECTICAL
MACHINES
BY
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
Asst.Professor
EEE
Dhanalakshmi College of Engg
INTRODUCTION INTRODUCTION
Definition :-
Design may be defined as a creative physical
realisation of theoretical concepts
Engineering design is the application of Science,
Technology and inventions to produce Various
machines to solve specified tasks with optimum
efficiency and economy.
The major considerations of a good design
� Cost effective
� Durable
� Quality
� Efficient
� Classification of design� Electromagnetic design
� Mechanical design
� Thermal design
� Dielectric design → design of insulators
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
Electromagnetic design:
Stator & Rotor
Rotating machine
1. Core
2. Teeth dimension
3. Winding & air gap
Stationary
Core & winding
V.BALAJI AP/EEE DCE
Mechanical design:
Rotating
FrameShaftbearings
Stationary
Tank (Transformer tank)
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
General design procedure
Main dimensions (decides voltage rating of the machine)
Rotating
D- diameter of armature (or) stator
L- Length of armature (or) stator are length.
Stationary:
Hw – height of the window
Hw – width of the window
Main dimensions depend on loading of the machine
ie
D & L α loading
Window
Total electric loading:
Total number of armature ampere conductors
the air gap (or) around the armature face.
Specific magnetic loading
Bav =
Specific electrical loading (ac)
DL
p
πφ
D
IzZac
π=
Similarities in Electric & Magnetic Similarities in Electric & Magnetic
circuits.circuits.
The path of flux is The path of flux is
called magnetic called magnetic cktcktThe path of Current is called The path of Current is called
electric electric cktckt..3.3.
The creation of flux is The creation of flux is
opposed by reluctance opposed by reluctance
of the of the cktckt..
Flow of current is opposed Flow of current is opposed
by resistance of the circuit.by resistance of the circuit.2.2.
The The mmfmmf creates flux creates flux
in a closed path.in a closed path.The The emfemf circulatescirculates
Current in a closed path.Current in a closed path.
1.1.
Magnetic CircuitsMagnetic CircuitsElectric CircuitsElectric CircuitsS.NS.N
oo
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
ContdContd……..
Flux density = Flux/ Flux density = Flux/
areaareaCurrent density = Current density =
current/area current/area 5.5.
Flux = Flux = mmfmmf / /
RelutanceRelutanceCurrent = EMF/ ResistanceCurrent = EMF/ Resistance4.4.
Magnetic CircuitsMagnetic CircuitsElectric CircuitsElectric CircuitsS.NS.N
oo
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
Differences between Electric and Magnetic Differences between Electric and Magnetic
CircuitsCircuits
Reluctance depends Reluctance depends
on total flux or flux on total flux or flux
density in the material.density in the material.
Resistance is independent of Resistance is independent of
current strength. current strength. 3.3.
Energy is needed only Energy is needed only
to create the flux but to create the flux but
not to maintain it.not to maintain it.
When current flows, the When current flows, the
energy is spent continuously. energy is spent continuously. 2.2.
Flux does not flow, Flux does not flow,
but it is only assumed but it is only assumed
to flow to flow
Current actually flows in the Current actually flows in the
electric electric cktckt..1.1.
Magnetic CircuitsMagnetic CircuitsElectric CircuitsElectric CircuitsS.S.
NoNo
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
Magnetic circuit:-
1. It provides path for flux lines
2.mmf creates flux against
Reluctance calculate:- in smooth armature
ysPole surface
Closed slotsArmature surfacews
Ws – width of slot
Wt – width of tooth
(i) For smooth armature closed type of slot are chosenV.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
Reluctance in open type of slot:-
Ws Wt
lg
ys
(without fringing flux )
flux liner
go
gg A
ls
A
ls
µ
µ
=
=
A
ls
µ=
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
Semi closed type:-
tg wLA ×=
( )ss wyL −×=
( )sso
gg wyL
LS
−=
µ
wt wsws
lg
ys
ys’Fringing flux
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
LyA
A
lS
sg
go
gg
×′=
=µ
( )ss wywL −×=
( )oso
gg wyL
lS
−=
µ
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
Reluctance in open type of slots (with fringing flux ):-
ssttss
sts
sg
go
gg
wywwwy
wwy
LyA
A
lS
−=⇒+=+=′×′=
=
δ
µ
ωs ωt
lg
ys
ys'fringing flux
ωs
( )δωδωω−−=′
+−=′1sss
ssss
yy
yy
( )kcswy ss −=Kcs – carter’s coefficient
Sg = lg/µoL(ys – kcs ws)
Gap contraction factor:- (kgs)
It is defined as the ratio between reluctance of air gap with slotted armature to reluctance of air gap with smooth armature.
Empirical relation:-
ksc (semi closed slots) =
Open slots:-wSlg /1
1
+
g
o
l
wy
yykcs
2
1log1
tan2 21
=
+−= −
ππ
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
V.BALAJI, B.E. M.Tech, (Ph.D), MIEEE, MISTE, MIAENG.
�� THANK YOU THANK YOU
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