2015 16th International Conference on Computational Problems of Electrical Engineering (CPEE) Lviv, Ukraine 142 Estimation of Supercapacitor Efficiency in Use for Resistance Welding Igor Pentegov, Volodymyr Sydorets E.O. Paton Electric Welding Institute of the NAS of Ukraine Kyiv, Ukraine magn@i.com.ua, sydorvn@gmail.com Iuliia Bondarenko Donbas State Technical University Lysychansk, Ukraine bondarenko.julie@gmail.com Oleksandr Bondarenko National Technical University of Ukraine «KвТv PolвtОМСnТМ InstТtutО» Kyiv, Ukraine bondarenkoaf@gmail.com Pavlo Safronov Odesa National Polytechnic University Odesa, Ukraine p.s.safronov@gmail.com Abstract—The appearing of supercapacitor internal resistance influence on efficiency of energy delivery in resistance welding circuit was studied in the paper. The dependencies of supercapacitor energy storage efficiency on load resistance were obtained. The limits of supercapacitor use for resistance welding area were determined. Keywords—Supercapacitor, equivalent series resistance, resistance welding, efficiency I. I NTRODUCTION Supercapacitors are effective storage elements which take their place between batteries and electrolytic capacitors. Their capacitance ranges from several farads to several thousands of farads. The main areas of supercapacitor application are electric transport, consumer electronics and power engineering. There are some substantial advantages of supercapacitors comparing to energy storages of other types. They have smaller size and weight than electrolytic capacitors of the same capacitance. They have higher rate of charge/discharge than batteries and are able to endure hundreds of thousands cycles of recharge. The advantages of supercapacitors make them attractive for the area of pulse welding which requires the energy storages with high capacitance, fast charge/discharge and long lifetime [1]. The known disadvantage of supercapacitors is quite high internal resistance (ESR), which ranges from tenths of milliohm to several hundreds of milliohms. The load resistance in welding circuit is within the range of tenths of milliohm – several milliohms [2]. Welding current may reach hundreds or even thousands amperes. So, the use of supercapacitors as energy storages in these conditions may not be efficient. The aim of this work is to estimate the influence of supercapacitor internal resistance on energy efficiency in welding circuit and to determine the limits of supercapacitor use for pulse welding area. II. SUPERCAPACITOR EQUIVALENT CIRCUITS Depending on study kind, supercapacitors can be represented in different ways [3]. The equivalent circuit shown in Fig. 1(a) represents main electrical properties of supercapacitor: C SCAP – electrical capacitance; ESR SCAP – equivalent series resistance; R L – leakage resistance; L P – parasitic inductance of electrodes and pins (must be taken into account at high frequencies). The equivalent circuit presented in the Fig. 1(b) is the simplest one but it reflects the most substantial electrical properties of supercapacitor, so, it may be considered as sufficient for supercapacitor efficiency estimation. The simplified structure of DC power supply for resistance welding with supercapacitor as energy storage is given in Fig. 2. Input Converter as a rule consists of rectifier, power factor corrector and transformer. It turns mains voltage into low DC voltage. Welding Current Regulator includes transistor converter which provides needed parameters of current pulses during welding. The load of the power supply is welded contact. The supercapacitor charge/discharge equivalent circuits, corresponding to the structure on Fig. 2, are shown in Fig. 3, where U IN – converted DC input voltage; R IN – equivalent (a) (b) Fig. 1. Supercapacitor equivalent circuits