Lec20_21_23-MagneticMaterialsInductance

Lec20_21_23-MagneticMaterialsInductance - ECSE 351...

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ECSE 351 Electromagnetic Fields McGill University – ECE Dept. - Prof. Milica Popovi ć Lectures 19, 20 & 21: Materials in Magnetic Field Objective: we want to be able to: Assess: how big are the magnetic forces and how can they be calculated, Find a way to define behavior of materials in magnetic field, Understand the need for magnetic circuit analysis, Use the concept of inductance for field analysis
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The Lorenz Force = total force on a point charge moving in an electric and a magnetic field McGill – ECE – ECSE 351 Electromagnetic Fields – Prof. M. Popovic FQ E Q v B =+ × GJ G G J G
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McGill – ECE – ECSE 351 Electromagnetic Fields – Prof. M. Popovic FQ E Q v B =+ × GJ G G J G 1927 Solvay physics conference
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Force on a differential current element – result: the Hall effect McGill – ECE – ECSE 351 Electromagnetic Fields – Prof. M. Popovic QvB QE = H Imagine charges moving in a certain direction within a thin conductor, with a permanent magnetic field perpendicular to the conductor surface. || VE d v B d 12 = = H + - B B F F v v J J 1 1 2 2 Q > 0 Q < 0 d d H E vB =
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The Hall effect is most pronounced in semiconductors. Hall-effect devices are commonly used to determine the type and concentration of free carriers of semiconductor samples. Gaussmeters (often called Teslameters) use a Hall element to measure magnetic flux density , by generating output voltage proportional to the magnetic field. Special attention is given to the design of the accompanying Hall-effect probes. In integrated circuits technology, Hall effect is used for sensors and switches. In sensors, the magnetic flux density through the Hall element determines the output voltage; in switches, it determines the switching state. Hall- effect sensor operation is robust with respect to environmental conditions. McGill – ECE – ECSE 351 Electromagnetic Fields – Prof. M. Popovic
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Linear Hall sensors- Their industrial applications include measurement of angle, current, position and distance, and pressure, force, and torque sensors. In automotive industry: * for active suspension control, * headlight range adjustment, * liquid level sensors, * power steering, . ... With very low energy consumption (a fraction of a mW), linear Hall sensors are more efficient and cost- effective than most inductive and optoelectronic sensors. McGill – ECE – ECSE 351 Electromagnetic Fields – Prof. M. Popovic
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Hall-effect switches are more cost-effective than most electromechanical switches. * commutation of brushless DC motors, * wheel speed sensors, * measurement of rotations per minute, * pressure switches, * position-dependent switches, etc. The automotive industry uses Hall switches, * in ignition and wiper systems, * door locks, * window raising controls, * retraction roof controls and for * break light switches. In the computer industry , this type of switch is used in keyboards.
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Lec20_21_23-MagneticMaterialsInductance - ECSE 351...

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