Electrical Engineering ⇒ Topic : Introduction of magnetic circuit

INTRODUCTION

Magnetic flux lines form closed loops. Magnetic circuit is defined as the closed path followed by flux lines. Electric circuit provides a path for electric current, whereas magnetic circuit provides a path for magnetic flux. The knowledge of magnetic circuit is very important in the design, analysis, and applications of electromagnetic devices like transformers, rotating electrical machines, and electromagnetic relays. 

Introduction

We have seen that magnetic lines of force form closed loops around and through the magnetic material. The closed path followed by magnetic flux is called a magnetic circuit just as the closed path followed by current is called an electric circuit. Many electrical devices (e.g. generator, motor, transformer etc.) depend upon magnetism for their operation. Therefore, such devices have magnetic circuits i.e. closed flux paths. In order that these devices function efficiently, their magnetic circuits must be properly designed to obtain the required magnetic conditions. In this chapter, we shall focus our attention on the basic principles of magnetic circuits and methods to obtain their solution

INTRODUCTION TO MAGNETIC FIELDS

        The magnetic effect of electric current was first discovered by Oersted in 1820. When a conductor carries an electric current, a magnetic field is produced around that conductor.

    In the course of his experiments,Oersted happened to lead a wire carrying current over a compass needle, and also parallel to it, as shown in Fig. (a). The needle was observed to deflect from its original position.On the other hand, when the wire was placed under the compass needle, the needle deflected in the opposite direction. Another example to shown the magnetic effect of electric current is shown in Fig. (b). The figure shows a current carrying conductor pierced through a sheet of paper held horizontal to the surface. If iron filings are sprinkled on the paper, the iron filings align themselves in concentric circles around the current carrying wire. From the above observations Oersted concluded that the magnetic field lines are circular around the wire.

                                          (a)                                                                                           (b)

                                                                             Figure