ABSTRACT
Transformer efficiency, regulation, and temperature rise are all interrelated. The core loss is a fixed loss, and the copper loss is a variable loss that is related to the current demand of the load. The copper loss increases by the square of the current and also is termed a quadratic loss. Maximum efficiency is achieved when the fixed loss is made equal to the quadratic loss, Transfer of heat by convection occurs when a body is hotter than the surrounding medium, which is usually air. The layer of air in contact with the hot body that is heated by conduction expands and rises, taking the absorbed heat with it. Heat dissipation, from the underside of a horizontal flat surface, depends upon area and conductivity. The minimum size of a transformer is usually determined either by a temperature rise limit, or by allowable voltage regulation, assuming that size and weight are to be minimized.
