CALCULATION OF TRANSFORMER LOSSES UNDER NON-SINUSOIDAL CURRENTS USING:TWO ANALYTICAL METHODS AND FINITE ELEMENTS ANALYSIS
An article discussing effects of non-sinusoidal currents to the transformer losses. This article was made through the effort of M.Yazdani-Asrami, M.Mirzaie and A.Shayegani-Akmal of Babol University of Technology, Babol, Iran.
Transformers are the most important component in power system and are interfaces between consumers and suppliers. Contemporary with ever-increasing electrical energy demand, the number and capacity of installed transmission transformers and especially distribution transformers are increasing. However, considering the point that the efficiency of these components is 97-99%, there was not enough attention to the amount of loss and performance of transformers. By considering the large number of transformers in transmission and distribution networks, it can be seen that the total power loss of these components is high. So, any reduction in loss of transformers would considerably reduce the total loss of electrical network and this will lead to optimum utilization of energy resources and helps environmental preservation.
In recent decades, many of transformers that was installed for supplying linear loads with full sinusoidal current at the first. gradually, their main loads have been exchanged with non-linear loads that produces harmonic current. Increasing the amount of harmonic contents of load current creates extra loss in windings and thus, lead to increase in their hot spot temperature, increase of stress in their insulations, reduction of insulation useful life and ultimately,reduction of transformer capacity.
Loads that produce harmonics in the electrical system are; rectifiers, electronic phase control, PWM drivers, UPS, cyclo converters, arc furnaces, adjustable speed drives, computers and ballast of fluorescent lamps in official center and large ventillation systems in commercial centers.