Indonesian Journal of Electrical Engineering and Computer Science Vol. 3, No. 1, July 2016, pp. 59 ~ 66 DOI: 10.11591/ijeecs.v3.i1.pp59-66  59 Received February 2, 2016; Revised May 25, 2016; Accepted June 10, 2016 Analysis of Step Up Transformer for Pulsed Electric Fields Generator Yoppy*, Mohamad Khoirul Anam, Yudhistira, Priyo Wibowo, Harry Arjadi, Hutomo Wahyu Nugroho, Haryo Dwi Prananto Research Center for Quality System and Testing Technology (P2SMTP) – LIPI Puspiptek Area Building 417, Tangerang Selatan, Indonesia *Corresponding author, e-mail: yoppy@lipi.go.id Abstract Pulsed electric fields (PEF) is a novel non-thermal food processing whose purpose is inactivating microbes while at the same time preserving food’s nutrition, color, and taste. This paper presents an analysis of step up transormer for PEF high voltage generator. To achieve the optimum PEF effects, the pulse shape should resemble a square, which is characterized by low voltage drop and fast rising time. Through simulations, it has been shown that higher transformer inductance results in lower voltage drop. However at some points, further increasing the inductance would only produces negligible improvements. Meanwhile fast rising time can be achieved by minimizing leakage inductance and parasitic capacitance. Moreover, maximum energy transfer to the load can be obtained by reducing winding resistances. Finally, a case of high voltage generator using ignition coil has been evaluated. Due to its high winding resistances, ignition coil seems to be not suitable for PEF applications. Keywords: pulsed electric fields, non thermal food processing, step up tranformer Copyright © 2016 Institute of Advanced Engineering and Science. All rights reserved. 1. Introduction One of conventional methods in food sterilization is using thermal processing. Although this method is very efficient in destroying bacteria, it also has some disadvantages, for example potentially reducing nutritional content as welll as altering the color, taste, and aroma of the food. To overcome those drawbacks, non thermal food processing methods are developed, such as pulsed electric fields. Pulsed electric fields (PEF) is basically short pulses of high voltage in order of tens of kilovolts applied to food. A PEF system consists of a treatment chamber where the food is placed. The chamber is usually small-sized and is connected to a pair of high voltage electrodes. When the voltage pulse is applied, a strong electric field of tens of kV/cm develops in the chamber. Such an intense electric shock causes the break down of microbe’s membrane. Because the applied voltage is short in duration, i.e in order of microseconds, temperature rise is insignificant. Therefore, sterilization purposes can be achieved while at the same time undesirable thermal side effects can be minimized. Several investigations have been done to compare the results of thermal processing and PEF methods. By choosing an appropriate voltage and frequency, PEF method can result in the same level of bacteria inactivation as that of thermal processing. Additionally, PEF is better in preserving the food pH level [1]. Other studies compare the effect of PEF and thermal processing [2] as well as high pressure [3] in degrading bacteria PME (pectin methyl estarase) in orange juice. The studies suggest that PEF is more effective in bacteria inactivation, and therefore the orange juice has a longer shelf life. Resilience of bacteria against PEF treatment depends on the structure and size of the bacteria [4]. Besides that, the electric field applied in the treatment chamber also plays a major role. This includes the pulse width, total processing time, and amount of energy delivered to the food [5]. There has been several implemented methods to generate a high voltage, such as solid state Marx Generator that can produce pulse voltage up to 6 kV at 1.6 kA [1, 2]. Another technique is using pulse forming network (PFN) [8]. In order to obtain an ideal pulse ouput, the impedance of PFN should be equal to that of the load. So, the output of PFN is highly sensitive to the variation of load impedance [9]. A high voltage pulse can also be generated by using high