SU1265952A1 - Inverter system - Google Patents

Abstract

The invention relates to a converter technique and can be used in installations of a multi-motor electric drive. The goal is to increase reliability, reduce losses and improve the harmonic composition of the output voltage. The device contains switches 1,2, connected to at least two thyristor inverters (I) 3. A pair of circuits from the retaining transistor 8, resistor 9 and the introduced additional source (yes) 10 is connected to the opposite terminals of input I 3 and inputs of the inverter system. The interrupt keys (L L 1.2 are bridged by a circuit from diode 12 and thyristor 13. The minimum reverse voltage applied to the thyristors AND 3 during the pause is equal to the DI 10 voltage. This voltage is assumed to be more or equal to the minimum time of 05 Sd UD SP 1C

Description

a setting for which the off time no longer changes with its further development. As a result, the frequency capabilities increase, and as the carrier frequency increases, the harmonic composition of the output voltage improves. 1 hp f-ly, 3 ill.

one

The invention relates to a conversion technique and can be used as an inverter system in a multi-motor drive system.

The aim of the invention is to improve the harmonic composition of the output voltage, increase reliability and reduce losses.

FIG. 1 shows a diagram of an inverter system; in fig. 2 — Pater control pulse diagrams and interrupter output voltage curves; in fig. 3 - diagrams explaining the work of retaining chains.

In the inversion system (Fig. 0), at least two inverters 3 are connected to the input terminals via the anode 1 and cathode 2 switches, consisting of alternating current connected to the bridge connected via the diode 4 connected by a reverse-diode 4 reactor. 7 reverse current diodes connected to the input of the inverter system by a direct current. A pair of circuits from the retaining transistor 8, resistor 9 and an additional source 10 are connected to the opposite terminals of the input of inverters 3 and the input of the inverter system. Anode The cathode keys 1 and 2 of the interrupter each consist of a forward connected. —Anode (cathode) transistor 11, shunted in the forward direction by a circuit from one or more diode 12 and thyristor 13.

Fig. 2 shows a diagram 14 of the chopper switching commands, a diagram 15 of the control pulses of the thyristors 13 of the switches, a diagram 16 of the control pulses of the transistors 11 of the switches, a voltage curve 17 between the opposite terminals of the inverter input 3 and an input of the inverter system, a voltage curve 18. the inputs of the inverters 3 and the diagram 19 of control pulses of the retaining transistors 8.

The inverter system works as follows.

5 The DC voltage in the chopper is converted into a pulse (curves 17 and 18) and fed to inverters 3, where it is converted into a three-phase pulse-width modulated 10, and the output frequency is determined by a set of the desired number, the pulses of the chopper, and the on-delay voltage inverter 3 thyristors relative to the front of the output

15 voltage breaker.

The chopper works as follows.

At the moment (FIG. 2)

20, the thyristors 13, and the source voltage is fed to the input of the inverter 3. In this case, all the own capacitances of the thyristors of the inverters 3 are charged, i.e. the entire capacitive inrush current is taken on

25 self thyristors 13. Then at time t, the transistors 1 1 turn on and the entire load of the driver is transferred to them in view of the fact that the voltage on the transistors 11

30.In the saturation mode it is less than the pad (1 voltage on a chain of diodes 2 and thyristor 13. Thus, accumulated by a wide base of thyristor 13 (during its activation),

, - gradually resolves, and at time t, to turn off the thyristor 13, it suffices to apply a small negative potential to its narrow base (control electrode) and it will close.

dd In this case, the transistor 11 and the thyristor 13 are closed at the same time. At time t, besides this, the transistors 8 are turned on, and the voltage (O, IE) of the additional sources 10 through

Claims (2)

The resistors 9 are applied in opposite to all the thyristors of the inverters 3, ensuring their accelerated switching off. 31 At any current overload (short circuit or capacitive surge) of transistors 11, they begin to enter the analog mode, and then the current goes to the thyristor 13, since in this case the voltage drop across the transistor P is greater than the circuit from the diodes 12 and thyristor 13. In the case of a short circuit, this mode continues until time t (Fig. 2), and, thus, the wide base of thyristors 13 is charged and the latter are not turned off. The chain of the retaining transistor 8, the resistor 9 and the additional source 10 operates as follows. At time t, (figs. 2 and 3), when switches 1 and 2 are turned off (diagrams 15 and 16), transistors 8 are turned off (diagram 19). In this case, if the current of any phase of the load is positive (directed to the load), then the anode reverse diode 7 of the same phase bridge opens, i.e. the phase of the load is connected to the negative input terminal, and negative voltages are applied to the thyristors 6 of this bridge: anodic Uofep Uio of the cathodic E + and, E + 0.1, 1 E. The fig. 3 shows voltage diagrams for anodic 20 and cathodic 21 thyristors 6 of a bridge of a phase with a positive current in it. With a negative current, the diagrams 20 and 21 change places. The minimum reverse voltage applied to the thyristors of the inverter 3, is equal to the voltage of additional sources. This voltage is assumed to be greater than or equal to the minimum voltage at which the off time does not change with further lowering. If the source voltage is on the order of 540 V, then it is quite sufficient for supplying 54V (oh, IE). In this case, in comparison with the known system (where Shutdown is performed without backwater), the pause time can be shortened by 2-4 times. As a result, the frequency capabilities increase, and as the carrier frequency increases, the harmonic composition of the output voltage improves. Shunting the transistors 11 in the short circuit mode with the thyristor 13 provides reliable protection for the transistors 11, and in the normal mode eliminates voltage dips at the output of the inverters during capacitive inrush currents during the switching on of the inverter thyristors. The organization of the backwater in the pauses of the input voltage of the inverters reduces the turn-off time of the inverter thyristors by 2.5-3 times and increases the carrier by the same time, and improves the harmonic composition of the output voltage. Claim 1. An inverter system comprising at least two inverter connected via anode and cathode transistors, each consisting of a main thyristor bridge connected through a reverse-dioded-shunt reactor, connected to alternating current connected to a reverse-current diode bridge the power input, a circuit from a retaining transistor and a resistor, which is different from the fact that, in order to improve the harmonic composition of the output voltage, the circuit is connected in the forward direction through The input source is valid to one of the opposite terminals of the power input of the inverters and the power input of the system, and another such circuit with an additional source is connected to the other terminals. 2. The system of claim 1, characterized in that, in order to reduce losses and increase reliability by protecting the anode and cathode transistors from short circuits, these transistors are bridged in the forward direction by a circuit of at least one diode and a thyristor. t, go