Application of Permanent Magnet: Application of Permanent Magnet are given in Table 2.1. These properties are: residual flux density Br, coercive magnetizing force Hc maximum energy stored (BH)max and resistivity. Type A material is cheap but heavy, and suitable for low-rated production-run motors. Types B and C materials are hard and can be given simple […]

### MAGNETIC CIRCUITS

## Permanent Magnet Definition

Permanent Magnet Definition: The Permanent Magnet Definition is an important excitation source (life long) commonly employed for imparting energy to magnetic circuits used in rotating machines and other types of electromechanical devices. There are three classes of permanent magnet materials (or hard magnetic materials) used for permanent magnet dc (PMDC) motors: Alnicos, ceramics (ferrites) and […]

## Hysteresis Eddy Current Loss

Hysteresis Eddy Current Loss: When a magnetic material undergoes cyclic magnetization, two kinds of power losses occur in it Hysteresis Eddy Current Loss which together are known as core-loss. The core-loss is important in determining heating, temperature rise, rating and efficiency of transformers, machines and other ac run magnetic devices. Hysteresis Loss Figure 2.18 shows a […]

## Energy Density Formula

Energy Density Formula: The Energy Density Formula of transformers, ac machines and several other electromagnetic devices are excited from ac rather than dc sources. With ac operation, inductance is effective even in steady-state operation. Often, the flux is determined by the impressed voltage and frequency, and the magnetization current has to adjust itself in accordance […]

## Magnetically Induced Emf and Force

Magnetically Induced Emf and Force: Magnetically Induced Emf and Force – Faraday’s law of induction, which is the integral form of the fourth Maxwell’s equation, is given as The integrated form of Eq.(2.15) for a coil of N turns is The positive direction of current in the coil is that direction which establishes positive flux […]

## Magnetic Materials Properties

Magnetic Materials Properties: Magnetic Materials Properties – From the magnetic point of view a material is classified according to the nature of its relative permeability (μr). All nonmagnetic materials are classified as paramagnetic,μr slightly greater than 1, and diamagnetic, μr slightly less than 1. For all practical purposes, μr of these materials can be regarded […]

## Magnetic Circuit Calculations

Magnetic Circuit Calculations: Normally magnetic circuit calculations involve two types of problems. In the first type of problem it is required to determine the excitation (mmf) needed to establish a desired flux or flux density at a given point in a magnetic circuit. This is the normal case in designing electromechanical devices and is a […]

## BH Curve Relationship

BH Curve Relationship of Magnetization Characteristic: In free space (also nonmagnetic materials), the permeability μ0 is constant so that BH Curve Relationship is linear. This, however, is not the case with ferromagnetic materials used in electric machines, wherein the BH Curve Relationship is strictly nonlinear in two respects saturation and hysteresis. Hysteresis non-linearity is the double […]

## Magnetic Circuit Basics

Magnetic Circuit Basics: The exact description of the Magnetic Circuit Basics is given by the Maxwell’s equations and the constitutive relationship of the medium in which the field is established. Such description apart from being highly complex is otherwise not necessary for use in electric machines wherein the fields (magnetic and electric) are slowly varying […]