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Topic 1 : Magnetic Concept and Transformer. Magnetism Magnetic Circuit Transformer Construction Transformer equivalent circuit Transformer test, efficiency and regulation. MAGNETISM. Magnetic field. A magnet has two poles – N and S
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Topic 1 : Magnetic Concept and Transformer • Magnetism • Magnetic Circuit • Transformer Construction • Transformer equivalent circuit • Transformer test, efficiency and regulation.
Magnetic field • A magnet has two poles – N and S • Shape of steel fillings on a sheet over a magnet are shown below.
Magnetic field • The shape and density of the chains formed enable us to form a mental picture of a magnetic field and lead to the idea of magnetic flux lines. • The density of the lines depends on the strength of the magnet. • The area in which the steel filling are affected by the magnet is become thinner further away from the magnet.
Characteristic of magnetic flux • The direction of flux is from North to South. • Each line of magnetic flux forms a closed loop. • Lines of electric flux never intersect. • Lines of magnetic flux are like stretched elastic cords, always trying to shorten themselves. • Lines of magnetic flux which are parallel and in the same direction repel one another.
Magnetic field of a current carrying conductor • Current going in (left) • Current coming out (right). • Solenoid.
S S Force N N Force on current carrying conductor • Flux of magnet and conductor • Interaction of flux produces force
Index finger FLUX Force on current carrying conductor Thumb FORCE Middle finger CURRENT • Left-hand rule
Electromagnetic induction • Two experiments performed by Michael Faraday. • Electric current could be produced by the movement of magnetic flux relative to the coil.
Index finger FLUKS Electromagnetic induction Thumb FORCE Middle finger CURRENT • Direction of induced emf. • Fleming’s right-hand rule. • Lenz’s law - The direction of an induced emf is always such that it tends to set up a current opposing the motion or the change of flux responsible for inducing that emf.
Basic Definitions • Permeability of different materials • Notice the nonlinearity
Comparison of electric and magnetic circuit • Since the magnetic circuit behaves in similar ways as an electric circuit, the laws of electric circuit are applicable to the magnetic circuit. • Ohm’s law equivalent : • F = ΦS. • Kirchoff law equivalent: • Φin = Φout • Total NI = Total Hl • A magnetic circuit can be redrawn as electric circuit equivalent to facilitate the analysis.