SU221811A1 - AUTONOMOUS INVERTER WITH ADJUSTABLE OUTPUT FREQUENCY - Google Patents

Description

A self-contained inverter with an adjustable 1 frequency output is known, containing sequentially connected and alternately operating thyristor cells, shunted by resistors.

The specified inverter does not allow a wide input voltage range.

The main distinguishing features of the proposed autonomous inverter is that, in order to increase the input voltage range and increase reliability, capacitors are connected in parallel with the indicated resistances.

FIG. 1 shows an inverter circuit with series-connected cells; in fig. 2 — multi-cell series inverter with valves turned on between the sections of the primary winding of the inverter transformer; in fig. 3 - multi-cell series inverter with series-parallel switching of cells; in fig. 4 — multi-cell series inverter with series-parallel connection of cells and with connection of switching capacitances between the middle points of the pair of gates; in fig. 5 - multi-cell series inverter with series-parallel connection of cells connected between sections of the primary winding of an inverter transformer.

The inverter contains series-connected cells 1-3 with thyristors 4-9 and shunting resistances 10-J2, in parallel with which capacitors are connected

J3-15.

In order to provide the possibility of powering multi-cell converters of increased frequency from a DC source with a voltage exceeding the permissible for

The valves of each cell, cell I, 2, 3 of the converter are connected in series for the sequential operation of individual cells of series or their groups. In this case, all valves 4–9 of the converter are turned on in series, but during each period of the output frequency only one valve or a group of valves of different cells is operated.

Inverter. On FIG. 1. Is connected to a source of direct current e-voltage through the smoothing inductors 16 and filter tanks 13-15, connected together in series through the sections of the primary winding 17-19 of the output transformer 20.

In order to evenly distribute the DC voltage between the filter containers 13-15, equalizing resistances 10-12 are connected in parallel with them. Each cell of the inverter contains two valves (4 and 5, 6)

torus 21, 22 and 23. All cells, as well as all valves are connected to each other in series. The load 24 is connected to the secondary winding 25 of the output transformer 20.

The device works as follows.

When the valve 4 is turned on, a negative voltage is applied to the upper phase of the primary winding 17 of the inverter transformer 20 relative to the midpoint, after which the switching capacitor 21 is recharged, at the end of which the voltage on the transformer 20 has the opposite sign. After the end of the oscillatory process, the valve 4 is turned off and the next valve belonging to any other cell is turned on, for example, the valve 6 of the cell 2. At the moment the valve 6 is turned on, the upper phase section of the primary winding 18 of the transformer 20 again has a negative voltage relative to the middle point: C, then the recharging of the switching capacitor 22 begins and the polarity of the voltage on the windings of the transformer 29 changes. Thus, during a period of time of turning on one valve before turning on the other voltage windings of the inverter transformer 20 nrohodit full cycle of its variations. After the alternating switching on and off of the gates 4, 7, 8 of all the cells is completed and the voltage on all the switching capacitors 21-23 changes its sign, the alternating switching on and off of the gates 5, 7, 9 of all the cells starts.

In this case, also when each valve is turned on, for example, 5, a positive voltage with respect to the midpoint will be applied to the lower phase of the primary section 17 of transformer 20, since the capacitor 22 remained positively positive after the valve 4 was quenched. This is equivalent to the negative voltage applied to the upper phase, which changes its sign during the recharging of the capacitor 21 and will be positive to the burning point of the valve, i.e. the process flows the same as when the valves 4, 6, 8 are turned on.

As a result, during the full cycle of operation of all the valves on the secondary winding 25 of the invertor transformer 20, we get "n Untimely voltage periods by the number of cells" n. The time of the impact of the reverse voltage on the valve, which is necessary for restoring its controllability, is more than in one cell parallel inverted org.

torus 2 1 + (n-1) times, where n is the number of cells, and b is the limit angle necessary to restore the controllability of the valve. For example, with three consecutively connected cells and, and the time allowed for the restoration of controllability of the valves is increased by 18 times. For thyristors, which have a recovery time of up to 30 µsec in one cell parallel inverter at the maximum frequency

will be equal to about 4000 Hz, and in this scheme, with three cell performance, the limiting frequency will be about 70 kHz.

Unlike simple cascade connection of rectifiers and conventional inverters used to increase the voltage, this inverter has the ability to alternately connect series-connected cells, while with a simple cascade connection, all cascade-connected elements are absolutely necessary . This difference makes it possible, along with the possibility of increasing the supply voltage, to maintain the properties

many cell circuits, i.e., to provide an increase in the time allowed for the restoration of control of the valves many times, which makes it possible to carry out ultrasonic frequency converters that feed

from a DC source of overvoltage. The difference in the circuit shown in FIG. 2, the primary winding sections 26, 27, 28 of the inverter transformer 29 are connected in series between the valves of the cells 30, 31, 32.

FIG. 3 is an inverter circuit diagram allowing powering from an overvoltage source and increasing the power of the inverter thanks to the best

using transformer windings. In this scheme, two valves in each cell 33, 34, 35 work simultaneously. For example, when cell 33 is operating, valves 36 and 37 are simultaneously turned on, while cell 34 is working, valves 38 and 55 are on, etc. After the valves have finished working, 40 41 E cell 35 again operates cell 33, but other gates 42 and 43 are turned on, etc. This ensures an even distribution of currents between parallel

operating valves 36-37, 38-39, 40-41 and reducing the effective value of the current flowing through the sections of the primary winding 44 of the inverter transformer 45 compared to the inverter of the same power, working according to the scheme shown in FIG. 1, but with doubled number of valves to two pairs of parallel connected.

In the diagram in FIG. 4, with the series connection of cells 46, 47, 46, switching capacitors 49 are connected between the middle points of two pairs of series-connected valves 50 of each cell, which, all other things being equal, can halve the number of filter tanks and sections of the cervical winding 51 of the transformer 52. The diagram in FIG. 5 cells 53, 54, 55 are connected between the sections of the primary winding 56 of the inverter transformer 57.

The subject invention 56

Christine cells, shunted reliability resistance, parallel to the indication of the multipliers, differing in the fact that, in order to increase the resistance, the condensation of the input voltage range and ry are connected.

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