SU788307A1 - Self-sustained inverter - Google Patents

Description

(54) AUTONOMY INVERTER

one

The invention relates to converter equipment, namely, autonomous inverters, and can be used. used, for example, in installations for the induction heating of metals.

Known autonomous inverters, made according to the scheme of parallel bridge inverter on thyristors. Such an inverter contains a power thyristor bridge, a smoothing choke and a switching capacitor, in parallel to which a load (inductor) 1 is connected.

The disadvantages of the inverter are poor starting characteristics and the difficulty of ensuring stable operation during discharges and load surges.

Also known is a series-parallel inverter, which contains a bridge of power thyristors, a smoothing choke, a capacitor with a load connected in parallel with it (inductor) and an additional capacitor, which is connected in series with the main capacitor. Inverters of the same type have the best dynamic properties and provide the possibility of a direct start 2.

The closest in technical essence to the proposed is

An autonomous inverter designed by DPF works in vacuum installations. In which there are two inductors, one of which ensures the melting of the metal and the other the formation of a metal ingot. Such an inverter contains a power thyristor bridge, a capacitor in the diagonal of the AC bridge, in parallel with which the first load (melting inductor) is connected, and at least two additional thyristors, between the common

point of which and one of the weekend

the main bridge terminals include an additional switching capacitor, in parallel with which the second load (crystallization inductor) is connected. If it is required to ensure the coordinated work of more than two

20 loads, the number of additional thyristors increases accordingly. This inverter retains all the disadvantages of a parallel inverter.

25 (in particular, poor dynamic characteristics), since it operates in current switching mode. one load on another with variable squash. Particularly complicated is its

30 transient operation in those

cases when the quality of the oscillating circuit of the load is high, which is exactly what is observed in induction heating installations, since in this case the amplitude of the voltage on the capacitor in the first half-wave after switching is so small that it does not provide satisfactory switching conditions.

The purpose of the invention is to improve the dynamic characteristics of the inverter during its operation on the circuit with high quality.

The goal is achieved by the fact that an autonomous inverter contains a triangle connected to the input terminals through a filter choke a thyristor bridge with a switching capacitor in a diagonal connected in parallel to a pair of output pins, and at least one chain of two series-connected thyristors, whose common point is Saved with one of the second pair of output pins, shunted by an additional capacitor, with the other pin of the second pair connected to one of the output pins of the first pair, provided with a parallel LC circuit connected in the diagonal of the bridge in series with the switching capacitor, and the point of connection of the latter with the LC circuit is connected to the specified output terminal of the second and subsequent pairs of output terminals.

In addition, in order to increase reliability, the Inverter is equipped with at least one parallel LC circuit connected in series with an additional capacitor and connected to a common point of these two series-connected thyristors.

The drawing shows the electrical circuit diagram of the inverter.

The circuit contains filter choke 1, power thyristors 2-7, switching capacitors 8 and 9, loads (inductors) 10 and 11, main 1C circuit 12 and, 13, additional LC circuit 14 and

15, power supply (rectifier)

16. Thyristors 4 and 5 are connected with load 10, thyristors 6 and 7 - with load 11, and thyristors 2 and 3 - with both loads. Thus, thyristors 4 and 5 pass only loads of current 10, thyristors b and 7 only loads of 11, and thyristors 2 and 3 pass currents of both loads.

Autonomous inverter works as follows.

If at the initial moment of time thyristors 2 and 5 alternately switch, forming a positive half-wave of current in load 10, and thyristors 3 and 4, forming a negative half-wave of current, then load 11 is de-energized, since thyristors .6 and 7 are closed. Actually in this mode.

the circuit operates as a series-parallel inverter, since the circuit consisting of capacitor 12 and throttle 13 has a capacitance shift close to 9 at the frequency of the inverter (V.

If it is necessary to turn on the load 11 and turn off the load 10, the control pulses as follows.

If the thyristors 2 and 5 are turned on at the moment preceding the switch, then at the moment of switching, the pulses are applied to thyristors 3 and 6. Switching occurs, and thyristor 5 is closed by discharging capacitors 12 and 8 through thyristor 3, and thyristor 2 is discharging the capacitor 12 through the uncharged capacitors 9 and 14 and the thyristor 6. Similarly, when the thyristors 3 and 4 are on, pulses are applied to the thyristors 2 and 7, and switching occurs, as a result of which the load 10 is disconnected due to the fact that the thyristors 4 and 5 are turned off and the load 11 is connected It is via thyristors 2 and 7 and b and 3, working in pairs, to the power source.

Further, the order of operation is repeated.

The installation is controlled so that the voltage at the output of the power supply rectifier corresponds to the total power of both loads (10 and 11), and the ratio of the duration of operation of groups 4, 5 and 6, to the pulse-width modulation (PWM) period of maintaining the specified power at each of the loads. The PWM period is selected from the process requirements. The switching period of the installation from load to load must be several times longer than the period of operation of the inverter.

Using cxeNttJ significantly improves the starting characteristics of the inverter and its dynamic characteristics in the mode of switching current from one load to another.

Claims (3)

1. A stand-alone inverter containing a thyristor bridge connected to the input pins through a filter choke in a diagonal connected in parallel to a pair of output pins, and at least one chain of two series-connected thyristors, whose common point is connected to one from the second pair of output pins, shunted by an additional capacitor, and the other output pins of the second pair are connected to one of the output pins of the first pair, characterized in that, in order to improve the dynamic characteristics actors, it is equipped with a parallel LC circuit connected to the bridge diagonal in series with a commutator; a common capacitor, the latter connecting to the LC circuit connected to the specified other output terminal of the second and subsequent pairs of output terminals. 2, the inverter according to claim 2, characterized in that, in order to increase reliability, it is provided with at least one additional parallel LC circuit connected in series with an additional capacitor and connected to a common point of these two series-connected thyristors. Sources of information taken into account in the examination 1. Sitnik N.Kh. Power semiconductor technology. M., Energie, 1968. 2.Berkovich E.I. and others. Thyristor converters of high frequency. L .; Energie, 1973. 3. USSR author's certificate on application 2604963/07, cl. H 02 M 7/515, 1978.