SU1524148A1 - Self-excited inverter - Google Patents

Abstract

The invention relates to a converter technique and can be used to power induction motors from a direct current source. The purpose of the invention is to reduce power losses by eliminating the recharging of switching capacitors. The device contains a thyristor bridge 1-6. The bridge distribution diodes 10-15 is connected to the nodes of the forced capacitor switching 16 and 17. Each of the nodes 16 and 17 consists of two controlled key elements 18, 21, 23, 26 and two diodes 19, 20, 24, 25. This embodiment of the nodes forced capacitor switching eliminates the pre-recharge of capacitors and eliminates the associated power loss. 2 hp f-ly, 2 ill.

Description

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The invention relates to converter equipment, and more specifically to autonomous inverters designed to convert direct current to alternating current, and can be used to power induction motors from a direct current source.

The aim of the invention is to reduce power losses by eliminating the recharging of switching capacitors.

Figure 1 presents the scheme of the autonomous inverter; Fig. 2 are diagrams of current and voltage changes on a switching capacitor.

The autonomous inverter contains a thyristor bridge 1-6 connected through filter reactors 7 and 8 to the positive and negative inputs of the power supply. Load 9 is connected to the output outputs. The distribution diode bridge 10-15 is connected to the output terminals of the inverter. Two nodes 16 and 17 of forced capacitor switching are included, the first 16 - between the anode groups, the second 17 - between the cathode groups of thyristor bridges 1-6 and distribution diodes 10-15, The npH nodes of the compelling capacitor switching consist of: the first of two connected in parallel chains formed in series in the first controlled key element 18 and the diode 19, and in the second from the diode 20 and the controlled key element 21 and the capacitor 22 connected between the common connection points of the key element 18 and the diode a 19 of the first chain and the key element 21 and the diode 20 of the second chain; the second of two connected in parallel chains formed in series, in the first, the controlled key element 23 and diode 24, and in the second, the diode 25 and controlled key element 26 and a capacitor 27 connected between the common connection points of element 23 the diode 24 of the first chain and the element 26 and the diode 25 of the second chain. As elements 18, 21, 23 and 26, transistors or dual-operation thyristors () can be used. The diagrams for changing the current 28 and the voltage 29 on the switching capacitor 122 (27) during the switching process are shown in FIG.

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Q When the inverter is connected to the power source through reactors 7 and 8, the distribution diode bridge 10-15, diodes 20, 19, 25 and 24, the capacitors 22 and 27 are charged with the polarity shown in Fig. 1. When two main thyristors are turned on , for example, 1 and 4, a current begins to flow through the circuit: the positive source of the power source - reactor 7 -. thyristor 1 - phases A and B of load 9 - thyristor 4 - reactor 8 - negative terminal of the power source. To transfer current from phase A to phase C, the thyristors 18 and 21 o are turned on. To thyristor 1, a reverse voltage is applied from the precharged capacitor 22 through diode 10, causing it to turn off. The load current then closes along the circuit: reactor 7 - thyristor 18 - capacitor 22 - thyristor 21 - diode IJO - phases A and B of load 9 - thyristor 4 - reactor 8 - power supply "Capacitor 22 is discharged by current 28 (Fig 2) loads and the voltage on it begins to decrease (curve 29, fig. 2). After delaying the time required for restoring the locking properties of the thyristor 1, the thyristor 5 is simultaneously turned on and the thyristors 18 and 21 are turned off. At the same time, the current in phase B of the load begins to increase, and in phase A it disappears. Falling current phase A protekj P g

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It goes through diode 20, capacitor 22, diodes 19 and 10, and charges capacitor 22 before the voltage preceding the switching process. When the current reaches phase C equal to the value of the current of phase B, the current in phase A decreases to zero, the charging process of the capacitor 22 ends, and the process of switching the current in phase A of the load ends. The load current is closed along the circuit: reactor 7 - thyristor 5 - phases C and B loads - thyristor 4 - reactor 8 - power supply. Turning off the thyristor 4 occurs in a similar way when turning on the thyristors 23 and 26. As a result of the periodic switching on and off of the thyristors 1-6, an alternating current is formed in the load

The switching process eliminates the preliminary recharge of the switching capacitor and, as a result, the associated power loss is eliminated. As a result, it allows

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1.5-2% increase in efficiency of autonomous inverter.

Claims (3)

Invention Formula 1, a stand-alone inverter containing a thyristor bridge connected to the input terminals through the filter reactors, the AC outputs of which are connected to the output terminals and outputs of the alternating current of the three-phase distribution diode bridge, as well as two nodes of forced capacitor switching, the first between the anodimms and the second is between the cathode groups of thyristor bridges and distribution diodes, with the key elements and a switching capacitor in each node, characterized in that. 48 In order to reduce power losses by eliminating the recharging of switching capacitors, each node of forced capacitor switching is made in the form of a bridge connected by a diagonal of direct current in accordance with distribution diodes, the diagonal of alternating current of which is switched to a switching capacitor, the first two common-phase arms are formed by diodes, the second two are fully controllable key elements. 2, the inverter according to claim 1, which differs from the fact that transistors are used as controlled key elements, 3. The inverter according to claim I, characterized in that two-step thyristors are used as controlled keys. Fie.2