1._Fundamentals_of_Magnetics_2011

# 1._Fundamentals_of_Magnetics_2011 - Fundamentals of...

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EEL 3211 © 2011, Henry Zmuda 1. Fundamentals of Magnetics 1 Fundamentals of MAGNETICS Revised Tuesday, May 17, 2011

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EEL 3211 © 2011, Henry Zmuda 1. Fundamentals of Magnetics 2 Magnetic fields provide the fundamental mechanism by which energy is converted from one from to another by means of: •motors (electrical energy è mechanical energy ) •generators (mechanical energy è electrical energy) •transformers (electrical energy è electrical energy )
EEL 3211 © 2011, Henry Zmuda 1. Fundamentals of Magnetics 3 Four basic principles: 1. A current flowing in a wire produces a magnetic field in the vicinity of the wire. 2. A wire in the presence of a time-varying magnetic field will induce a voltage across the wire (transformer action). 3. A current-carrying wire in the presence of a magnetic field experiences a force exerted on the wire (motor action) 4. A a wire moving in the presence of a magnetic field has a voltage induced upon it (generator action). Each of these will be considered in detail.

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EEL 3211 © 2011, Henry Zmuda 1. Fundamentals of Magnetics 4 The fundamental postulate governing the electrical behavior of magnetic fields is given by Ampere’s law: ! H i d ! " C # ! = I enclosed ! H : Vector Magnetic Field (amperes/meter) ! " : Vector Closed Path of Integration (meters) I enclosed : Net Current ecnlosed by C
EEL 3211 © 2011, Henry Zmuda 1. Fundamentals of Magnetics 5 I I ! H C ! H i d ! " C # ! = I Side view (along axis)

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EEL 3211 © 2011, Henry Zmuda 1. Fundamentals of Magnetics 6 I ! H r ( ) C r Right Hand Rule Convention ! H I
EEL 3211 © 2011, Henry Zmuda 1. Fundamentals of Magnetics 7 I ! H r ( ) C ! H i d ! " C # ! = 2 " rH r ( ) = I # H r ( ) = I 2 r r

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EEL 3211 © 2011, Henry Zmuda 1. Fundamentals of Magnetics 8 We assumed that field produced by the wire exists in air . The strength of the magnetic field produced also depends on the material in which the field exists. Certain materials, called ferromagnetic materials , have the property of confining the field inside of it. Ferromagnetic materials are characterized by their permeability , μ . The for air (or free space): 7 41 0 o Henrys meter μμ π == ×