Unit 3 of the document covers principles of alternating current machinery, including inductance, capacitance, and impedance. It discusses types of electrical machines like alternators and transformers, their construction, working principles, and efficiency. Additionally, it outlines three-phase induction motors, detailing their construction, operating principles, and applications.

1. Unit 3
Principles of Alternating current
machinery
by
P. V. Thokal
Assistant Professor
Sanjivani College of Engineering, Kopargaon

2. Unit 3 Syllabus

3. Introduction to Inductance, Capacitance and Impedance
1. Inductance(L): The property of an electric conductor or circuit that
causes an electromotive force to be generated by a change in the
current flowing. Unit is Henry, Circuit symbol L
2. Capacitance (C): It is the ability of a component or circuit to collect
and store energy in the form of an electrical charge. Unit is Farad
Symbols

4. 3. Impedance(Z): It is the effective resistance of
an electric circuit or component to alternating
current, arising from the combined effects of
ohmic resistance and reactance. Unit is Ohm.
Z= V/I

5. Identify the Components

6. Introduction Single and Poly Phase supply
1. Alternator: Alternator is an electrical machine
which generates AC supply. it is also called as
AC GENERATOR.
Types of Alternators:
1. Single Phase Alternator:
• Generates 1 phase supply
2. 3 Phase Alternator:
• Generates 3 ph. Supply

7. Benefits of 3 phase system
• Its possible to take single phase supply
From 3 phase supply.
• 3 phase machines are self start machines,
Single phase machines are NOT self start.
• 3 phase machines have higher power factor.
• 3 phase machines have higher efficiency.
• Three phase motors have uniform torque ,
Single phase motors have pulsating torque.
• The output of 3 phase machine is always greater than single phase
machine of same size.

8. Single Phase Transformer
• TRANSFORMER = TRANSFORM + POWER
• Definition: A transformer can be defined as a static device which
helps in the transformation of electric power in one circuit to electric
power of the same frequency in another circuit.
• Working Principle: it works on the Principle of mutual induction,
according to Faraday’s laws of Electromagnetic Induction.
• Construction: i) Iron Core ii) Windings (Copper or Al)

9. • Circuit Symbols:
• Types of single phase Transformer (According to
Construction)
1. Core Type Transformer 2. Shell Type Transformer

10. Images of 1 phase & 3 Phase Transformer

11. Difference between Core and Shell Type transformer

12. EMF equation of a single phase transformer

13. • Transformation Ratio (K):
• Losses in Transformer:

14. • The Equation for Hysteresis loss is given as:
Ph = η * Bmax
n * f * V
Where Ph = hysteresis loss (W)
η = Steinmetz hysteresis coefficient, depending on
material (J/m3)
Bmax = maximum flux density (Wb/m2)
n = Steinmetz exponent, ranges from 1.5 to 2.5,
depending on material
f = frequency of magnetic reversals per second (Hz)
V = volume of magnetic material (m3)

15. • The Equation for Eddy current loss is
given as:
Pe = Ke * Bmax
2 * f2 * t2 * V
Pe = eddy current loss (W)
Ke = eddy current constant
B = flux density (Wb/m2)
f = frequency of magnetic reversals per
second (Hz)
t = material thickness (m)
V = volume (m3)

16. • Rating of a transformer: Transformer rating is
expressed in VA or KVA or MVA
• From KVA rating of transformer we can calculate
primary and secondary current at full load.
KVA rating = V1I1/1000 from this we can write
• I1 = KVAX1000/V1
• I2= KVAX1000/V2
• Why transformer ratings are expressed in
VA/KVA/MVA???

17. • Efficiency of a Transformer
• Regulation of a transformer

18. • Auto Transformer:

19. Advantages:
1. Saving of Copper due to only one Winding.
2. Small in size
3. Higher efficiency than two winding
transformer
4. Better Voltage Regulation
Disadvantages:
• Not useful for HIGH VOLTAGE applications,
due to no isolation between Primary and
Secondary windings.

20. Applications of Auto Transformers
• Compensating voltage drops by boosting supply
voltage in distribution systems.
• Auto transformers with a number of tapping are
used for starting induction and synchronous
motors.
• Auto transformer is used as variac in laboratory or
where continuous variable over broad ranges are
required.
• Used as Dimmerstat.

21. Comparison between Autotransformer and Two winding transformer

22. Three Phase Induction Motor
Construction:
• Stator: Outer Body

23. • Rotor: Rotating Part
• Types:
1. Squirrel Cage Rotor
2. Slip ring (Wound) Rotor

24. • Rotating Magnetic Field (RMF): When we apply a
three-phase supply the 3 phase stator winding a rotating
magnetic field is produced which rotates in synchronous
speed.

25. • Synchronous speed (Ns): It is the speed at which the
Rotating Magnetic Field( RMF) rotates.
• Slip speed: The difference between the
synchronous speed and the actual speed of the rotor is
known as the slip speed.

26. Torque Equation of thee phase I.M.
• The torque produced by three phase induction motor depends upon
the following three factors:
1. magnitude of rotor current 2. flux which interact with the rotor of
three phase induction motor 3. power factor of rotor

27. Torque Slip Characteristics of 3 phase I.M.

28. Power Stages of 3 Phase I.M.

29. Applications of Squirrel cage and Slip Ring I.M.
• Squirrel cage IM is constant speed motor with
Moderate torque…
Applications: ????????
• Slip Ring IM has high starting torque and
variable speed
Applications: ????????

30. Thank You