1. Single Phase Transformers ELE 2103 Electrical Machinery1

2. Transformer Ideal Transformer Practical Transformer Equivalent Circuit
Concept of flux leakage,
Representation of Primary, Secondary & Core Impedances
Equivalent Circuit
Representation of Elements
Exact, Approximate
Exercise

3. Ideal Transformer – No Load
Pry & Sec windings have no resistance
Core has infinite permeability (zero reluctance)
No leakage or losses of any kind Im V1 Ø E1 E2 V2 N1 N2

4. Practical TransformerØ
Mutual Flux X
Primary Leakage
Flux
L1
Secondary
Leakage
Flux
L2 X
Windings have definite resistance values
Occurrence of Losses
Copper Loss (Pry & Sec)
Core Loss (Hysteresis Loss & Eddy current Loss)
Primary & Secondary Leakage Flux

5. Practical Transformer - Primary
Primary Leakage Flux L1 X
Primary Side
I1 sets up leakage flux L1 , links with primary only
Leakage flux L1 induces an self induced emf eL1, thus opposing current I1
eL1 is treated as voltage drops across fictitious reactance placed in series
X1 = primary leakage reactance
Primary leakage reactance drop = I1 X1 = I1  L1
Primary Side Impedance Z1 = R1 + j X1 R1 X1

6. Practical Transformer - Secondary
Leakage Flux L2 X
Secondary Side
I2 sets up leakage flux L2 , links with secondary only
Leakage flux L2 induces an self induced emf eL2, thus opposing current I2
eL2 is treated as voltage drops across fictitious reactance placed in series
X2 = secondary leakage reactance
Secondary leakage reactance drop = I2 X2 = I2  L2
Secondary Side Impedance Z2 = R2 + j X2 R2 X2

7. Core
Confining the flux set up, to the magnetic material path
Responsible for Hysteresis loss & Eddy current loss
Hysteresis Loss minimized by high grade material such as silicon steel
Eddy current loss minimized by stacks of thin laminations RC XM Io
Im = Magnetising current component Ic Im
Ic = Core loss current component
Io = No load current

8. Practical Transformer Representation
Core Ø N1 N2 E1 E2 V2 V1 R1 X1 R2 X2 Rc Xm Ø N1 N2 V2 V1 R1 X1 R2 X2
Ideal

9. Practical Transformer - No LoadRc Xm Ø N1 N2 V2 V1 R1 X1 R2 X2
Ideal Io E1 E2 Ic Im
Primary Side
Secondary Side