IX International Conference Industrial Engineering and Environmental Protection 2019 (IIZS 2019) October 3 rd -4 th , 2019, Zrenjanin, Serbia __________________________________________________________________________________________ HIGHER HARMONICS OF CURRENT CAUSED BY THE OPERATION OF ROLLING MILL Vladimir Šinik 1 , Željko Despotović 2 , Slavica Prvulović 1 , Eleonora Desnica 1 , Jasmina Pekez 1 , Jasna Tolmač 1 , Ivan Palinkaš 1 1 University of Novi Sad, Technical Faculty “Mihajlo Pupin”, Zrenjanin, Serbia 2 Institute “Mihajlo Pupin“, Belgrade, Serbia e-mail: sinik.vladimir@gmail.com Abstract: Three-phase controlled rectifiers have a wide range of applications, from small rectifiers to large. They are used for electro-chemical process, many kinds of motor drives, traction equipment, controlled power supplies, and many other applications. A simple analytic method of calculating higher harmonics of current generated by a three phase bridge rectifier at its network end is represented in this paper. This method is used for calculating higher harmonics of current with all inductance relationships of the circuits of the alternating and direct ends of a three phase bridge rectifier, at various rectifier loads and at various thyristor control angles. Key words: higher harmonics, rolling mill INTRODUCTION One of the most characteristic tendencies in the development of electromotive drives of cylindrical dwellings and their respective auxiliary drives is based on the large application of thyristor rectifiers for powering the armature and the excitation of their drive single-stroke engines. The installed power of thyristor rectifiers of some larger roller bearings reaches up to 100 MW and even more. Facilities equipped with industrial electronics components operate back to the electrical network [1-9]. The return operation of rectifier drive continuous rolling mills, which are the subject of this paper, manifested in the form of taking a reactive power from the network and network load with a higher harmonics current. Higher harmonics with network impedance create more harmonics in the network voltage. Distorted voltage has the adverse effect of the consumers who are supplied from such a network. Therefore, the method for the determination of harmonics in the current drawn from the network indicated consumers seems very current. Rolling is a continuous process of metal processing, whereby the piece is passed between two rollers and changes its shape. The length increases, and reduces the cross-section. The rolls are placed in the roller housing and rotate around their longitudinal axis. When rolling, the piece is passed through the gap of the roller. Rollers rotate in the opposite direction (Fig. 1) [4]. Figure 1. Scheme of multistage tandem strip for continuous cold rolling of sheet metal 50