Topic 1 : Magnetic Concept and Transformer

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# Topic 1 : Magnetic Concept and Transformer - PowerPoint PPT Presentation

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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Presentation Transcript
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
• 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.

### MAGNETIC CIRCUIT

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.