The thyristor inverters with the capacitors in the power circuit are designed for the electronic welding apparatuses, the plasmatrons power sources and so on. All these inverters are efficient and functional only in the limited load range, that is the essential defect, and this is restricted by their use range. In particular, such inverters are non - serviceable at the idle running and in the small loads range. It should be noted, it is talked on the inverters on the reverse - blocking thyristors, which are being blocked at the natural current fall down to the zero, or they are needed the reinforced switching [1]. The thyristor inverters of such type, which have been suggested earlier, for the load range extension are used the additional block, having provided the latitudinal and pulse control of the load current in the wide range [2]. The linear external characteristics are needed for the stable work of the welding load. So, it is quite possible to provide the linear external characteristics in the power sources of the inverter type with the capacitors in the in the power circuit at the latitudinal and pulse control, having only the 2 - 3 - multiple stress factor [1], that results in the proportional increase of the apparatus rated capacity. Besides, the two parallel circuits presence of the switching capacitor (SC) recharge, inevitably, results in the constant component appearance in the transformer current, which has been described in the [2] diagram, that it is needed the considerable increase of the transformer overall dimensions, in order to avoid its saturation. The new diagram of the thyristor inverter with the capacitors in the power circuit has been suggested in [3], and it has been given in the figure 1. The suggested apparatus diagram is consisted in the 1 ÷ 4 thyristor bridge, having connected to the direct current (DC) diagonal to the power source 5, having shunted by the filter capacitor 6. The primary winding 7 of the transformer 8 has been inserted into the 1 ÷ 4 thyristor bridge of the alternating current (AC) diagonal, sequentially, with the switching capacitor 9. The secondary winding 10, sequentially, with the load current sensor 11 has been connected to the diode rectifier 12, the direct current (DC) outputs of which have sequentially been connected to the choke 13 to the load 14. Besides, the apparatus is contained the expansion range control block 15 and the control system 16, having made with the latitudinal and pulse control, and having closed by the negative feedback along the current by the signal from the above - mentioned load current sensor 11, having connected to the corresponding control system input 16, the corresponding outputs of which are connected to the thyristors´ driving points of the 1 ÷ 4 thyristor bridge.
The expansion range control block 15 has been made by the principle of the transmission, having accumulated in the electromagnetic energy inductance from the source to the receiver, and it, moreover, is contained, as the electric power source, the additional winding 17 of the transformer 8, having connected to the diode bridge 18, the direct current (DC) diagonal of which has been shunted by the smoothing capacitor 19 and the voltage sensor 20. Besides, the above - mentioned the direct current (DC) diagonal of the diode bridge 18 has been loaded on, sequentially, the joining circuit from the current sensor 21, the inductance 22, and also the transistor switch 23, having connected to the direction of the conducting current. The corresponding filter capacitor 6 outputs have been connected to, in parallels, the transistor switch 23 through the pick - off diode 24. The driving point of the transistor switch 23 has been connected to the microcontroller 25 output of this switch control. The corresponding microcontroller 25 inputs have been connected to the current sensor 21 output and also to the differential amplifier 26 output, the direct input of which has been connected to the voltage sensor 20 output, but the inverting input has been connected to the load current sensor 11 output.
Firstly, the circuits are absent, which are in parallels of the primary winding 7 of the transformer 8, in the suggested apparatus, that is provided the constant component absence in the above - mentioned winding. Secondly, it is being observed the Id / f = const ratio, where f - the inverter frequency, Id - the load current, at the load current increase, that it is provided the linearity and the high rigidity of the external characteristics at the voltage control at the expense of the power source.
References
- L.T. Magazinnik, "The Single - Phase Power Sources of the Inverter Type with the Capacitors in the Power Circuit". The Electromechanics. The News of the Institutes of Higher Education, № 6, Novocherkassk town. 2003, p.p. 21...24;
- O.G. Bulatov, A.I. Tzarenko, V.D. Polyakov, "The Thyristor and Condensing Power Sources for the Electrotechnology". - M.: The EnergoAtomPublishing House, 1989 - p. 200;
- "The Thyristor Inverter with the Capacitors in the Power Circuit". The Patent of the Russian Federation № 2334346 dated from 20.09.2008, the author Magazinnik L.T.
The work was submitted to international scientific conference «Priorities for Science, Technology and Innovation», Egypt (Sharm el-Sheikh), November 20-27, 2008. Came to the editorial office оn 04.05.2009