Introduction about the electrical machines

dc machines basics

1. Introduction Class

2. MODULE 1 PRINCIPLES OF ENERGY CONVERSION Faraday's law of electromagnetic induction -singly and doubly excited magnetic field systems -EMF and torque production in rotating machines. MODULE 2 DC GENERATORS Construction – Windings – Principle of operation – Types – Characteristics. Armature reaction and commutation - parallel operation-Applications MODULE 3 DC MOTORS Principle of operation – Types – Characteristics – Starting and Speed control –Various testing- Applications MODULE 4 TRANSFORMERS Construction – Principle of operation – Types – phasor diagram of practical transformer on no load and load – Equivalent circuit –Voltage regulation and efficiency- Auto transformer.-Applications MODULE 5 TRANSFORMER TESTING Testing of transformers –Polarity, open circuit, short circuit and Sumpner‟s test –Three phase transformers connections- Parallel operation Syllabus 19UEE303 - Electrical Machines – I 2

3. What Is Electricity? Form of energy involving the flow of electrons All matter is made up of atoms Center called a nucleus Positively charged particles - protons Uncharged particles - neutrons Surrounded by negatively charged particles – electrons Number of electrons = number of protons 19UEE303 - Electrical Machines – I 3

4. What is an Electromotive Force? Force that acts on the electrons to make them move in a certain direction - voltage Work done on a unit electric charge Unit : volts (joules/ coulombs) Electrical power - Rate at which energy is being used or generated Unit: watts Energy - rate at which work is being done Unit: joules (J) (watt-second) Direct current (DC) -   does not change direction  AC current - charges continually change direction 19UEE303 - Electrical Machines – I 4

5. What is Electric Current? Rate of flow of electrons in a conductor Unit : Ampere (coulombs per second) 19UEE303 - Electrical Machines – I 5

6. History of Electricity Benjamin Franklin - In 1752, prove that lightning was electrical, he flew a kite during a thunderstorm 6 19UEE303 - Electrical Machines – I Thomas Edison - In 1879, the American inventor was finally able to produce a reliable, long-lasting electric light bulb Nikola Tesla - In 1887, developed an Induction Motor

7. 19UEE303 - Electrical Machines – I 7

8. Magnetic circuit 19UEE303 - Electrical Machines – I 8 The path in space through which magnetic flux passes Uniform cross-sectioned iron core Magnetic field within the toroid core is uniform

9. Terms involved in Magnetic Circuits Magnetomotive force F = N I Magnetic flux φ Reluctance R Permeability µ Magnetic flux density B Magnetic field intensity H 19UEE303 - Electrical Machines – I 9