Cost reduction by interchanging the location of the windings in distribution transformers with HV copper winding and LV aluminum winding Juan C. Olivares-Galvan 1,2 * ,† , Rafael Escarela-Perez 1 , Serguei Maximov 1,3 , Salvador Magdaleno-Adame 4 and Pavlos S. Georgilakis 5 1 Departamento de Energia, Universidad Autonoma Metropolitana-Azcapotzalco, 02200, D.F., Mexico 2 On sabbatical leave at the Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, T6G 2V4, Canada 3 On sabatical leave from Programa de Graduados e Investigacion en Ingenieria Electrica, Instituto Tecnologico de Morelia, Michoacan, 58120, Mexico 4 Engineering Department, Pennsylvania Transformer Technology, Inc., Canonsburg, 15317, PA, USA 5 School of Electrical and Computer Engineering, National Technical University of Athens, GR 15780, Athens, Greece SUMMARY According to the conventional winding configuration of distribution transformers, denoted as L-H, the low voltage (LV) winding is located internally and the high voltage (HV) winding is located externally. This paper proposes a new winding configuration, denoted as H-L configuration, according to which the location of windings is interchanged, that is, the HV winding is located internally and the LV winding is located externally. In the designs of transformer analyzed in this paper, the HV winding is manufactured with copper conductors and the LV winding with aluminum sheets. We have modified our transformer design program to analyze the new H-L configuration. Transformers ratings from 30 to 112.5 kVA are considered to show the cost reduction trend. The H-L and L-H configurations are compared on the basis of the following parameters: mean length of HV winding, mean length of LV winding, weight of HV conductor, weight of LV conductor, material cost, and total owning cost. As a result of the proposed design change, transformer manufac- turers save material and reduce cost. Transformers cost reductions are especially important in the competitive environment of transformer companies around the world. Copyright © 2014 John Wiley & Sons, Ltd. key words: transformer design; cost reduction; transformer windings; L-H configuration; H-L configuration; copper; aluminum 1. INTRODUCTION In order to successfully compete in a global economy, transformer manufacturers need to continuously improve transformer design to save material and reduce cost. Because it is easier to insulate, traditionally the low voltage (LV) winding is placed closer to the core and the high voltage (HV) winding covers the LV winding [1–23]. In this paper, this conventional arrangement of windings is called L-H configuration. Authors of [1–23] use the L-H configuration for various purposes, which are not explicitly mentioned here for the sake of space. This is a list of references that could be substantially increased, but we just want to emphasize that there is not a single publication proposing the H-L configuration. Our paper proposes a design improvement capable of reducing the distribution transformer cost while ensuring the fulfillment of all constraints in three-phase distribution transformers using rectangular windings. In this paper, the HV winding is placed closer to the core, and the LV winding covers the HV winding. This arrangement of windings is called H-L configuration. In Figure 1, we can appreciate the differences between both winding configurations. *Correspondence to: Juan C. Olivares-Galvan, Departamento de Energia, Universidad Autonoma Metropolitana-Azcapotzalco, 02200, D.F., Mexico. † E-mail: jolivares@correo.azc.uam.mx Copyright © 2014 John Wiley & Sons, Ltd. INTERNATIONAL TRANSACTIONS ON ELECTRICAL ENERGY SYSTEMS Int. Trans. Electr. Energ. Syst. (2014) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/etep.1985