Faraday law of Induction

Faraday law of Induction

The voltage induced across the secondary coil may be calculated from Faraday law of Induction, which states that:

where Vs is the Current’s Instantaneous voltage, Ns is the secondary coil’s number of turns,. And is the magnetic flux flowing through a coil turn. The flux is the product of the magnetic flux density B and the area A through which it cuts,. If the turns of the coil are Oriented Perpendicular to the magnetic field lines. The area is fixed because it is equal to the Cross-sectional area of the Transformer core,. But the magnetic field changes over time depending on how the primary is excited. The Instantaneous voltage across the primary winding in an ideal Transformer equals. Because the same magnetic flux flows through both the primary and secondary coils.

Taking the ratio of the two equations for Vs and Vp gives the basic equation for stepping up or stepping down the voltage

The primary Functional Characteristic of any Transformer is Np/Ns, also referred to as the turns ratio. This can Occasionally be expressed as the reciprocal, Ns/Np, in the context of step-up Transformers. A transformer with primary and secondary windings of 100 and 150 turns, respectively,. Is said to have a turns ratio of 2:3, rather than 0.667 or 100:150, which is how turns ratio is Typically Expressed.

An elementary transformer has two windings mounted on top of a core made of soft iron or silicon steel. Both the core and the windings are isolated from one another. Thin, soft iron or iron with a low magnetic flux resistance makes up the core. The magnetic flux was connected to the winding. The primary winding is the one connected to the supply main,. And the secondary winding is the one connected to the load circuit.

Although in the actual construction the two windings are usually wound one over the other,. For the sake of simplicity, the figures for analyzing transformer theory show the windings on opposite sides of the core, as shown below Simple Transformer

When primary winding is connected to an ac supply mains, current flows through it. Since this winding links with an iron core, so current flowing through this winding produces an alternating flux in the core. Since this flux is alternating and links with the secondary winding also, so induces an emf in the secondary winding.

The frequency of induced emf in secondary winding is the same as that of the flux or that of the s supply voltage. The induced emf in the secondary winding enables it to deliver current to an external load connected across it. Thus the energy is transformed from primary winding to the secondary winding. By means of electro-magnetic induction without anychange in frequency. The flux of the iron core links not only with the secondary winding but also with the primary winding, so produces self-induced emf in the primary winding:

This induced in the primary winding opposes the applied voltage. And therefore sometimes it is known as back emf of the primary. In fact the induced emf in the primary winding limits the primary current in much the same way that the back emf in a dc motor limits the armature current.

Transformation ratio

The ratio of secondary voltage to primary voltage is known as the voltage transformation ratio. And is designated by letter K. i.e. Voltage transformation ratio.

Current ratio

The ratio of secondary current to primary current is known as current ratio and is reciprocal of voltage transformation ratio in an ideal transformer.

V1I1 = Input VA

V2I2 = Ouput VA

V1I1 =  V2I2

V2/V1 = I1/I2 = K