1. Introduction to Electrical Machinery
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
• Generators
 AC, DC
• Motors
 AC (Single Phase, Three Phase), DC
• Transformers
 AC (Single Phase, Three Phase)

2. • Transfers energy from one electrical circuit to another without
change in frequency.
• Static Device working on principle of electromagnetic
induction
• Electric Circuits linked by common magnetic core
• Applications
 Electric power systems
 Power transmission, Distribution Networks
 Electronic Circuits
 Electric Traction
Transformers
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal

3. Primary Side Secondary Side
Core
V1Supply side V2 Load sideN1
N1 = Number of turns on primary
N2
N2 = Number of turns on secondary
Representation
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal

4. Physical Model
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal

5. I1
E1
E2 V2
I2
LOADV1
Ø
• Magnetic Core : Flux path
• Flux Linkages : Primary & Secondary
• Induced Emf : Primary – Self Induced Emf
& Secondary – Mutually Induced Emf
Operation
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal

6. Yoke
LV winding
Insulation
HV winding
Limbs
Core
Winding crossover
Primary &
Secondary windings
Laminations
Construction – Core Type
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal

7. Side Limbs
Central Limb LV winding
Insulation
HV winding
Yoke
Core
Insulation
Secondary
Winding
Yoke
Terminals
Laminations
Construction - Shell Type
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal

8. tsin,Core flux m ωφ=φ
)
2
π
t(sinNω
dt
d
Nf, eInduced em m −ωφ=
φ
−=
11111 2),
2
sin( NfNEtEe mmmm where φπωφ
π
ω ==−=
m11 fN44.4E, φ=EmfInducedPry
m22 fN44.4E, φ=EmfInducedSec
emf equation
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
2
φNf2
2
E
EEmfinducedSelfofvalueRMS
ωφNEEmfinducedselfofvalueMaximum
m11max
1
m11max
π
==
=

9. k==
1
2
1
2
N
N
E
E
(Transformation Ratio)
N2 > N1 : Step Up type
N1 N2
V1 V2
E2 > E1
V2 > V1, I1 > I2
V1 V2
N2 = N1 : 1:1 type
E2 = E1
V2 = V1, I1 = I2
N2 < N1 : Step down type
V1 V2
E2 < E1
V2 < V1, I1 < I2
Transformation Ratio
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal

10. A 250 kVA, 11000 / 415 V, 50 Hz, 1φ transformer has 80 turns on the
secondary. Determine (a) rated primary and secondary currents (b) primary
turns (c) maximum flux (d) emf induced per turn
Ans: (a) 22.73 A, 602.41 A (b) 2120 turns (c) 23.37 mWb (d) 5.1886 Volts / turn
Exercise
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal