06-10-2012, 03:54 PM
Transformer Parameter Laboratory
Transformer Parameter Laboratory.docx (Size: 284.26 KB / Downloads: 29)
Transformer
A device transferring electric energy from one circuit to another through inductively coupled conductors (the transformer coils) is called transformer.
Electromagnetism
This property is associated with Ampere’s Law which states that when current ‘i’ pass through a conducting wire it generates a magnetic field of intensity ‘H’ in the direction according to the right hand rule.
Magnetic indunction
Magnetic induction is explained by the law named Faraday’s Law. The Law states that When a Magnetic flux by a magnet is moved between a loop of wire it induce an electric force ‘e’ which cause current to flow if the flux ( φ) is changing. (Due to movement of magnet)
If the Magnet is kept stable then flux stays the same and no current ‘I’ flows in the loop.
An inverse of Faraday’s law known as ampere’s law also work , According to right hand rule the magnetic field generated by flowing current opposes the increasing flux.
Working of transformer
Transformer work after Ampere Law and faradays law occurs together.
Primary winding is the current driving winding whereas magnetic driven winding is known as secondary winding. As a single wire conducting current can’t be strong enough so a tightly wound coil is used as primary and secondary. More Turns Create larger ‘H’ magnetic field intensity.
Real Transformer
Real transformers have many losses which ideally should not be there.Few of them are described here.
Winding resistance
Current flow through the windings and causes conductors heat up because of their resistive property. Material of the coil creates additional winding resistance and losses.
Hysteresis losses
A non-liner phenomenon in which driving force of two opposite direction differs is named as term hysteresis. Magnetic hysteresis relates to how the properties of a material are affected by that material being magnetized and then demagnetized. When ‘H’ magnetic field Intensity is applied to the core which is a magnetic material, its domain aligns itself to increase the flux (B) of the core. After the saturation position all the domain is aligned and any increase in ‘H’ will not affect ‘B’. Each time the magnetic field is reversed, a small amount of energy is lost due to hysteresis within the core. For a given core material, the loss is proportional to the frequency, and is a function of the peak flux density to which it is subjected.
Eddy currents
Ferromagnetic materials are also good conductors, and a core made from such a material also constitutes a single short-circuited turn throughout its entire length. Eddy currents therefore circulate within the core in a plane normal to the flux, and are responsible for resistive heating of the core material.