**What is a Transformer?**

**Why voltage is required to be raised or lowered?**

**Working Principle of Transformer:**

**The transformer functions on the principle of Faraday’s Law of Electromagnetic Induction. The law states that if a conductor is placed in a varying magnetic field the voltage is induced in the conductor. When the alternating voltage is fed to the primary, the flux varying in magnitude and direction gets linked to the primary and the secondary winding of the transformer.**

**depends on the rate of change of the flux and number of turns in a coil. According to the Lenz’s Law the induced EMF in a coil always opposes the applied voltage. The induced EMF in a coil can be expressed as;**

*induced EMF***e = – N dФ/dt**

Ideally, the flux produced in the primary must get linked to the secondary without any leakage. However, practically all the flux produced in the primary does not link to the secondary and the some parts of the flux is lost. The magnetic core made of Cold Rolled Grain Oriented (CRGO) is more efficient for transferring the flux to the secondary winding. Also, the

**of CRGO core is less.**

*hysteresis loss*If the transformer is ideal, the flux generated by the primary winding gets linked to the secondary and primary and there is no leakage flux. However, this is an ideal condition and practically some of the flux gets leaked and links to the other parts of the transformer.The flux links in the core material induce emf which further cause heat loss in the core because of eddy current. The loss is called the eddy current loss. The magnetic core is laminated to reduce the

*eddy current loss.*

The primary winding is fed sinusoidal voltage.The sinusoidal voltage is alternating voltage and the current flowing in the primary set up magnetic flux in the core. The flux travels through the core and gets linked to the secondary and primary. The varying flux induce EMF in the primary and secondary. The magnitude of the EMF induced in the primary and secondary is as given below.**Ep = 4.44 Np fФm**

**Es = 4.44 Ns fФm**

**Where,**

Ep = Induced EMF in primary winding

ES = Induced EMF in secondary winding

Np = Number of turns in primary winding

Ns = Number of turns in the secondary winding

f = Frequency

Фm = Flux in the core

The transformer core can carry the flux up to its maximum rated capacity. The CRGO core can carry flux up to 1.9 Tesla. If the flux increases above 1.9 Tesla the core may get saturated and the output voltage may get distorted.

The transformer functions pretty well as long as the flux remains constant. The flux density depends on the ratio of voltage/ frequency.

**Turns ratio and voltage transformation ratio of Transformer :**

EMF equation of the transformer is as given below.**Ep = 4.44 Np fФm ——-(1)**

**Es = 4.44 Ns fФm ———(2)**

**Dividing equation (2) By (1) we get,**

**Es/Ep = Ns/ Np ———(3)**

**Es and Ep is almost equal to the primary and secondary terminal voltage if the winding resistance and the leakage reactance is ignored.**

**Es= Vs and Ep= Vp**

**Vs/Vp = Ns/ Np = K —-(4)**

**Where,**

**K is the voltage transformation ratio.****The input power of the transformer is almost equal to the output power.**

**Vs x Is = Vp x Ip**

**Vs/Vp = Ip/Is ———(5)**

**From equation (4) and (5) we get**

**Vs/Vp = Ns/Np = Ip/Is = K**

**The turns ratio is defined as the ratio of primary turns to secondary turns.**

**Turns ratio = Np/Ns= 1/K**

**In a step-down transformer,**the numbers of turns in the primary is more than the numbers of turns in the secondary.

**In a step-up transformer, the numbers of turns in the primary(Np) is less than the numbers of turns in the secondary(Ns).**

**Related Posts on Transformer**

**EMF Equation of Transformer****Single Phase Transformer and Applications of Single Phase Transformer****Why is the core of a power transformer grounded?****Dry Type Transformers: Types and Applications****Core Type Transformer****Shell Type Transformer**

You may also include all the necessary test procedures carried on transformer