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1. Design of Rotating Electrical Machines Subject code: EET 3186 Semester: 6 th 1 Lecture 1

2. Course Plan INTRODUCTION DC MACHINE CONSTRUCTIONAL DETAILS DC machine windings Problem solving Exercises for students AC MACHINE CONSTRUCTIONAL DETAILS AC machine windings Problem solving Exercises for students Constructional details of ceiling Fan and its winding design approach Design exercise problems for students 2 Lecture 1

3. Introduction 3 Lecture 1 Classification of DC machines DC machines Separately excited machine Self excited machine Shunt Series Compound

4. Classification of DC machines 4

5. Different parts of a DC machine Basically DC machines are made up of the following parts Yoke armature 5 Lecture 1 Pole shoes Field windings Armature core Armature Windings commutator Brushes Other than these electrical parts there are also some mechanical Parts such as shaft and bearings. Interpoles

6. Different parts of DC machine 6 Lecture 1

7. The Yoke 7 Lecture 1 Forms the outer structure of the machine. Provides the magnetic path for the flux outside the air gap. Supports the pole shoes and interpoles. Also it provide s the base for mounting the machine.

8. Cross sectional view of a dc machine 8 Lecture 1 Base for mounting

9. Contd … 9 Lecture 1

10. Armature It is the rotating part of the machine. It is the part of the machine where the electro - mechanical energy conversion takes place. Provides a low reluctance path for the flux in the air gap. 10 Lecture 1

11. Flux Path in the machine. 11 Lecture 1 Number of closed magnetic paths are equal to the number of poles. For production of a symmetrical magnetic field the field windings are wound in such a way that they produce alternate magnetic poles.

12. Armature core 12 Lecture 1 Armature core is made up of a number of circular stampings which are put together on the shaft to form the core. The stampings are laminated to increase the resistance of the core. By increasing the resistance eddy current loss in the armature core can be reduced.

13. Commutator Facilitates the current collection from the armature conductors. Converts the alternating current induced in the armature circuit conductors into unidirectional current in the external load circuit. The commutator consists of a number of copper segments which are electrically isolated from each other. Each commutator segment is connected to an armature conductor. 13 Lecture 1

14. Brushes Brushes are used for current collection from the commutator. Brushes are generally made up of carbon due to its high electrical conductivity as well as its inherent lubricating property. Generally brushes are spring loaded. 14 Lecture 1

15. 15 Lecture 1 Contd … Carbon brushes with copper springs

16. 16 Lecture 1 END of Lecture 1