Explanation of Voltage Regulation of Transformer

Say an electrical power transformer is open circuited, means load is not connected with secondary terminals. In this situation, the secondary terminal voltage of the transformer will be its secondary induced emf E₂. Whenever full load is connected to the secondary terminals of the transformer, rated current I₂ flows through the secondary circuit and voltage drop comes into picture. At this situation, primary winding will also draw equivalent full load current from source. The voltage drop in the secondary is I₂Z₂ where Z₂ is the secondary impedance of transformer. Now if at this loading condition, any one measures the voltage between secondary terminals, he or she will get voltage V₂ across load terminals which is obviously less than no load secondary voltage E₂ and this is because of I₂Z₂ voltage drop in the transformer.

Expression of Voltage Regulation of Transformer

Expression of Voltage Regulation of Transformer, represented in percentage, is