The voltage regulation is the percentage of voltage difference between no load and full load voltages of a transformer with respect to its full load voltage.
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 terminalvoltage of the transformer will be its secondary induced emf E2. Whenever full load is connected to the secondary terminals of the transformer, ratedcurrent 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 voltagedrop 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 getvoltage 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, represented in percentage, is
Equivalent impedance of transformer is essential to be calculated because the electrical power transformer is an electrical power system equipment for estimating different parameters of electrical power system which may be required to calculate total internal impedance of an electrical power transformer, viewing from primary side or secondary side as per requirement. This calculation requires equivalent circuit of transformer referred to primary or equivalent circuit of transformer referred to secondary sides respectively. Percentage impedance is also very essential parameter of transformer. Special attention is to be given to this parameter during installing a transformer in an existing electrical power system. Percentage impedance of different power transformers should be properly matched during parallel operation of power transformers. The percentage impedance can be derived from equivalent impedance of transformer so, it can be said that equivalent circuit of transformer is also required during calculation of % impedance.