Lecture 01Electro Mechanical System1 Electro- Mechanical System

Course: Electro-Mechanical Systems Lecture 01Electro Mechanical System2 Instructor: Shahid Anwar Text Book: Electrical Machines, Drives,and Power System Author: Theodore Wildi (6 th Edition) Publisher: Pearson Education

Brief Description: Lecture 01Electro Mechanical System3 Course is designed to provide students with an understanding of:  Working of transformers;  The general principles of electromechanical machine operation, rotating magnetic fields, and power conversion;  Design process for sizing, powering and controlling rotational machines;  Methods for calculating and measuring machine parameters;  A general overview of variable speed and dc machine drives

Lecture 01Electro Mechanical System4 Chapter 2 Fundamentals of Magnetism

Magnetic Field Lecture 01Electro Mechanical System5  Whenever a magnetic flux  exists in a conductor or component, it is due to the presence of a magnetic field intensity H, given by: H = U/l Where: H = magnetic field intensity [A/m] U = magnetomotive force acting on the component [A] or (ampere turns) l = length of the magnetic circuit [m]

Magnetic Flux Density Lecture 01Electro Mechanical System6  For a magnetic flux , there exists a magnetic flux density, B, given by B =  /A Where: B = flux density [T] (tesla)  = flux in a component [Wb] (weber) A = cross section area [m2]

B-H curve in vacuum Lecture 01Electro Mechanical System7  In free space, the magnetic flux density B is directly proportional to the magnetic field intensity H and is given by: B = µ o H  The constant of proportionality for free space is called the permeability constant, µ o  µ o = 4  x10 -7 H/m [henry/meter] (also called permeability of vacuum.)

Lecture 01Electro Mechanical System8  The flux density is influenced by the magnetic property of the material in which the flux passes  instead of specifying a permeability for every material, a relative permeability is defined, µ r = µ / µ o  relative permeability is unitless B = µ o µ r H  for many materials, the relative permeability is not constant but varies nonlinear w.r.t. flux density B Determining Relative Permeability

Lecture 01Electro Mechanical System9 Determining Relative Permeability  Example Determine the relative permeability of relay steel (1% silicon) at a flux density of 1.4 T requires a magnetic field strength of 1000 A/m  One can find the relative permeability in a material by taking the ratio of the flux density in the material to the flux density that would have been produced in free-space.

Determining Relative Permeability Lecture 01Electro Mechanical System10  Following diagram shows the saturation curves of a broad range of materials from vacuum to permalloy, one of the most permeable magnetic material known