Abstract—Determination of power transformer dimension associated with theoretical calculation and manufacturers’ testing procedures. Built for various users, the transformers are calibrated strictly using standards such as ANSI/IEEE C57.110 and IEEE C.57.12.01 1989. However, none of the calibration and testing considered harmonic situations in depth. Problems of harmonics are unique and rise exponentially since the 1970s. The RMS value of current is higher under harmonics condition, and the calibration and testing of power transformer is no longer applied because the current becomes nonlinear. The additional losses in steel cores, and windings translated into higher operational temperatures could lead the transformers to permanent malfunction through several causes like core saturation and explosion of windings. This paper examines the inclusion of harmonic current in determining core dimension of a three phase power transformer. The differences of Area Product, power rating, and apparent power in transformer operating with sinusoidal and harmonic current are mentioned. In the end, this paper provides sufficient mathematical explanation in justifying the need to alter the dimension of a power transformer to work in harmonics surrounding.

Index Terms—Core, Currents, Harmonics, Nonlinear loads, Power transformers.

Syafrudin Masri is an Associate Profesor and a senior lecturer at the School of Electrical and Electronics Engineering, Universiti Sains Malaysia Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia (e-mail:syaf@eng.usm.my).
Muhammad Mokhzaini Azizan is a Ph.D candidate at School of Electrical and Electronic Engineering, Universiti Sains Malaysia Engineering Campus,14300 Nibong Tebal, Penang, Malaysia (e-mail: mokhzainiazizan@yahoo.com.my).
Mohamad Kamarol Mohd Jamil is with the Electrical Engineering Department, Universiti Sains Malaysia Engineering Campus, 14300 NibongTebal, Penang, Malaysia (e-mail: eekamarol@eng.usm.my).

Cite: Syafrudin Masri, Muhammad Mokhzaini Azizan, and Mohamad Kamarol Mohd Jamil, "Determining Power Transformer Core Dimension Under Nonlinear Load Operation," International Journal of Computer and Electrical Engineering vol. 3, no. 5, pp. 739-742, 2011.