TRANSFORMER Transformer is electromagnetic static electrical equipment (with no moving parts) which transforms magnetic energy to electrical energy. It consists of a magnetic iron core serving as magnetic transformer part and transformer cooper winding serving as electrical part. The transformer is high efficiency equipment and its losses are very low because there isn’t any mechanical friction inside. Transformers are used in almost all electrical systems from low voltage up to the highest voltage level. It operates only with alternating current (AC), because the direct current (DC) does not create any electromagnetic induction. Depending on the electrical network where the transformer is installed, there are two transformer types, three-phase transformers and single phase transformers. The operation principle of the single-phase transformer is: the AC voltage source injects the AC current through the transformer primary winding

TRANSFORMER CIRCUIT DIAGRAM

The AC current generates the alternating electromagnetic field The AC current generates the alternating electromagnetic field. The magnetic field lines are moving through iron transformer core and comprise the transformer secondary circuit. Thus the voltage is induced in the secondary winding with same frequency as voltage of the primary side. The induced voltage value is determine by Faraday’s Law. Where, f → frequency Hz N → number of winding turns Φ → flux density Wb

Applications of Single Phase Transformer The advantages of three single-phase units are transportation, maintenance and spare unit availability. The single-phase transformers are widely used in commercial low voltage application as electronic devices. They operate as step down voltage transformer and decrease the home voltage value to the value suitable for electronics supplying. On the secondary side rectifier is usually connected to convert AC voltage to the DC voltage which is used in electronics application

Copper Loss in Transformer Copper loss is I2R loss, in primary side it is I12 R1 and in secondary side it is I22R2 loss, where I1 and I2 are primary and secondary current of transformer and R1 and R2 are resistances of primary and secondary winding. As the both primary & secondary currents depend upon load of transformer, copper loss in transformer vary with load.

Core Losses in Transformer Hysteresis loss and eddy current loss, both depend upon magnetic properties of the materials used to construct the core of transformer and its design. So these losses in transformer are fixed and do not depend upon the load current. So core losses in transformer which is alternatively known as iron loss in transformer can be considered as constant for all range of load.

IDEAL TRANSFORMER An ideal transformer is an imaginary transformer which does not have any loss in it, means no core losses, copper losses and any other losses in transformer. Efficiency of this transformer is considered as 100%. Ideal transformer model is developed by considering a transformer which does not have any loss. That means the windings of the transformer are purely inductive and the core of transformer is loss free. There is zero leakage reactance of transformer. As we said, whenever we place a low Reluctance core inside the windings, maximum amount of flux passes through this core, but still there is some flux which does not pass through the core but passes through the insulation used in the transformer.

EXTRINSIC SEMICONDUCTOR The semiconductor in which impurities are deliberately added to the pure semiconductors is called extrinsic semiconductor. The process of adding impurities to the pure semiconductor is called doping. Doping increases the electrical conductivity of semiconductor. Extrinsic semiconductor has high electrical conductivity than intrinsic semiconductor. Hence the extrinsic semiconductors are used for the manufacturing of electronic devices such as diodes, transistors etc. The number of free electrons and holes in extrinsic semiconductor are not equal. Types of impurities: Two types of impurities are added to the semiconductor. They are pentavalent and trivalent impurities. Pentavalent impurities: Pentavalent impurities are those which have 5 valence electrons. The various examples of pentavalent impurity atoms include Phosphorus (P), Arsenic (As), Antimony (Sb), etc Trivalent impurities: Trivalent impurity atoms have 3 valence electrons. The various examples of trivalent impurities include Boron (B), Gallium (G), Indium (In), Aluminum (Al).

CLASSIFICATION Based on the type of impurities added, extrinsic semiconductors are classified in to two types. 1. N-type semiconductor 2. P-type semiconductor N-type semiconductor: When pentavalent impurity is added to an intrinsic or pure semiconductor (silicon or germanium), then it is said to be an n-type semiconductor. Pentavalent impurities such as phosphorus, arsenic, antimony etc are called donor impurity. Let us consider, pentavalent impurity phosphorus is added to silicon as shown in below figure. Phosphorus atom has 5 valence electrons and silicon has 4 valence electrons. Phosphorus atom has one excess valence electron than silicon. The four valence electrons of each phosphorus atom form 4 covalent bonds with the 4 neighboring silicon atoms. The fifth valence electron of the phosphorus atom cannot able to form the covalent bond with the silicon atom because silicon atom does not have the fifth valence electron to form the covalent bond.

P-Type semiconductors p-type semiconductors have a larger hole concentration than electron concentration The term p-type refers to the positive charge of the hole. In p-type semiconductors, holes are the majority carriers and electrons are the minority carriers. When the trivalent impurity is added to an intrinsic or pure semiconductor (silicon or germanium), then it is said to be a p-type semiconductor. Trivalent impurities such as Boron (B), Gallium (G), Indium (In), Aluminum (Al) etc are called acceptor impurity since these accept one electron from the neighboring atom to complete the covalent bond

THANKS