Magnetic Circuits and Magnetic Materials KALOL INSTITUTE OF TECHNOLOGY & RESEARCH CENTER PRESENTATION ON Magnetic Circuits and Magnetic Materials Guided By:- Kiran Patel sir subject:- Elements of Electrical Design Enrollment no:-130260109020 130260109024

1.1 Introduction to Magnetic Circuits

Simple magnetic circuit. Figure 1.1 1-3

Magnetic circuit with air gap. Figure 1.2 1-4

Analogy between electric and magnetic circuits Analogy between electric and magnetic circuits. (a) Electric circuit, (b) magnetic circuit. Figure 1.3

Air-gap fringing fields. Figure 1.4

Simple synchronous machine. Figure 1.5

1.2 Flux linkage, Inductance, and Energy

Faraday’s Law When magnetic field varies in time an electric field is produced in space as determined by Faraday’s Law: Line integral of the electric field intensity E around a closed contour C is equal to the time rate of the magnetic flux linking that contour. Since the winding (and hence the contour C) links the core flux N times then above equation reduces The induced voltage is usually refered as electromotive force to represent the voltage due to a time-varying flux linkage.

+ - e(t) N The direction of emf: If the winding terminals were short-circuited a current would flow in such a direction as to oppose the change of flux linkage.

(a) Magnetic circuit and (b) equivalent circuit for Example 1.3. Figure 1.6

Magnetic circuit with two windings. Figure 1.8

1.3 Properties of Magnetic Materials

1.4 AC Excitation

Excitation phenomena. (a) Voltage, flux, and exciting current; (b) corresponding hysteresis loop. Figure 1.11

CORE LOSSES Hysteresis Losses: hysteresis loss is proportional to the loop area (shaded). Figure 1.13 Eddy Current Losses: Time-varying magnetic fields give rise to electric fields in the material resulting in induced currents. These induced currents cause Eddy Current Losses. These losses can be reduced by using thin sheets of laminations of the magnetic material.

1.5 Permanent Magnets

1.6 Application of Permanent Magnet Materials

Magnetization curves for common permanent-magnet materials. Figure 1.19

Portion of a B-H characteristic showing a minor loop and a recoil line. Figure 1.21