Design of power transformer is a systematic and detailed procedure aimed at the best electrical performance, efficient heat, and strong mechanical and economic. The design is based around critical components such as the core, windings, yoke, and structural frame. The starting point of the core design is to choose high permeability materials such as silicon steel to reduce hysteresis losses and increase magnetic flux. Structurally compact and efficient flux distribution is achieved by dimensional ratios such as core width-to-depth and window width-to-depth calculations. As the transformer window area is not fixed, the transformer window is required to accommodate high-voltage (HV) and low-voltage (LV) windings together with insulation and cooling provisions to minimize copper losses and effective heat dissipation. Calculation of the number of turns and conductor cross-sectional areas of the winding is done based on voltage, current, and the thermal limits is called winding design. Losses and voltage regulation are also evaluated to factors such as winding resistance, reactance, and leakage flux. The proportion of the yoke is configured to minimize flux leakage and balance the core. Next, all components are integrated into the transformer frame, taking into account space for insulating, cooling ducts, and structural integrity in order to absorb vibration and stress. At every step in the design, the durability, safety, and long-term, efficient operation are ensured by precise calculations and engineering judgment.