PER UNIT RESISTANCE, LEAKAGE REACTANCE AND IMPEDANCE VOLTAGE DROP

Full-load voltage of a transformer can be expressed as a fraction of the full-load terminal voltage.

Let I_1fl be the full-load primary current, I_2fl be the full-load secondary current, V₁ be the rated pri-mary voltage and V₂ be the rated secondary voltage.

Per unit resistance drop of a transformer

∴      

Per unit reactance drop of a transformer

Per unit reactance drop of a transformer is called per unit reactance and it is given by

Per unit impedance drop of a transformer is called per unit impedance and it is given by