SU436419A1 - SINGLE PHASE INVERTER - Google Patents

Description

one

The known schemes of single-phase inverters with a stepped output voltage curve do not provide a sufficiently good approximation of the shape of the curve to a sinusoidal one.

In order to improve the shape of the output voltage curve, the anodes of the cut-off diodes of the thyristor cells are connected to the primary winding sections of the transformer.

FIG. 1 is a schematic diagram of the proposed inverter, and FIG. 2 is a diagram of the formation of the output voltage.

The inverter contains: the main thyristors of the inverter 1-4, the thyristors of the step voltage transformer of the secondary winding of the transformer 5-12, the primary section of the transformer 13-16, the secondary section of the transformer, cut off, diodes 21-24, reverse current diodes 25, 26, switching capacitors 27, 29, filter choke 30.

The inverter power circuit consists of primary and secondary circuits. The primary circuit has a partitioned primary winding of the transformer with an equal number of turns in the middle sections 14 and 15, each of which is greater than any of the equal sections 13 and 16 equal in the number of turns.

The outer sections of this winding are connected through separating diodes 21-24 to the anodes of the thyristors 1-n4. Two secondary windings with an unequal number of turns (let the number of turns in winding 17 be less than the number of turns in winding 18) are alternately connected to the load via thyristors connected anti-parallel. The switching of the current in the primary circuit of the inverter is dried up by capacitors 27, 28, 29.

The turn-on diagram of the inverter thyristors is shown in Table. one.

Table 1

The first impulse of the control device includes thyristors 1, 5. At the same time, sections 13 and 14 of the primary winding with the number of turns of Wi-fWi are connected to the power source of the EP and the load is applied to the first positive half-cycle of the output voltage:

and

Н1

w + wi

At the same time, serially connected switching capacitors 27-29 are charged to a voltage of 2Ep, with the indicated polarity. The second pulse includes thyristors 4, 7 and a positive potential of series-connected capacitors 27-29 is applied to the cathode, and a negative potential is applied to the anode 1, and the thyristor 7 is closed. At the same time, the thyristor 5 is locked, since a positive voltage is applied to its cathode relative to the anode, induced in the winding 17, and the second voltage level is formed on the load:

ff W

-on 7,:, „

IFj-b Wi

ir, u7 ,, and „, and„ ,.

Series-connected switching capacitors 27-29 are recharged to a common voltage of 2Ep.

The third impulse includes thyristors 2, 7. In this case, series-connected switching capacitors 28, 29 are connected to thyristor 4 with a negative polarity for it and it is locked, and capacitors 28 and 29 are recharged to a value slightly greater than 2Ep em. , induced in the winding 18 when connected to section 14 of the power source EP, is applied to the thyristor 7 in the opposite direction and it closes, and a third output voltage stage is formed on the load:

 R

and „, -

Hj p

The ratio of the numbers of turns of the secondary and primary windings of the sections is assumed as

that the t / H3 H2 control device turns on the thyristors 3, 7 and the positive potential of the capacitor 28 through the open thyristor 3 is applied to the cathode, and the negative potential to the anode 2, and the thyristor 7 is closed. In the winding 17, a negative voltage is applied to the thyristor 5 and it is also closed, and the switching capacitor 28 is recharged to a voltage equal to 2Ep. Pa load the fourth stage of the output voltage:

J -.

t-h -. int

H4

C

which is higher than the voltage of the UnaP pulse of the control device turns on thyristors 2, 5. In this case, the switching capacitor 28 is connected to the thyristor 3 with a polarity negative to it and the thyristor 3 is locked, and the capacitor 28 is recharged. The thyristor 7 is locked, as a positive voltage is applied to its cathode relative to the anode, induced in the winding 18 and

and - E

 - g -PW,

The sixth impulse of the control device includes thyristors 4, 7, thyristor 2 is closed by the negative voltage of series-connected switching capacitors 28 and 29 relative to it,

the latter are recharged to a voltage greater than the EP. The electromotive force induced in the winding 17 switches off the thyristor 5, and the power supply voltage is applied to the primary winding section 15 and 16 with the number of turns

W / 4-W7 /, THEN

Gz

not" .

 + Wl

By the seventh impulse of the control device, the thyristors 1, 5 are turned on and the positive potential of series-connected capacitors 27-29 is applied to the cathode, and the negative potential is connected to the anode 4 and the thyristor 5 is closed. The thyristor 7 is closed by the negative voltage induced in the winding 18, and the series-connected capacitors 27-29 are recharged to a voltage equal to 2Ep, and

..W,

and,,

-EPWi + Wi

Understanding the formation of negative

the half-period of step voltage can be seen from the further consideration of the thyristor diagrams on the table. 1 and no difficulties. Inverter can work on load

active-inductive nature. To return the load's reactive energy to the power source, it is necessary to additionally introduce reverse diodes 25, 26 into the primary circuit of the inverter circuit, and into the secondary circuit, depending on the power factor of the load, one or two switching nodes consisting of a capacitor 31, 32 and connected to two consecutively oppositely connected thyristors

(in Fig. 1 are shown in broken lines).

The addition of two secondary windings and two pairs of anti-parallel connected thyristors in the inverter circuit allows an increase in the number of output stages

four strains. So, adding (fig. 1)

6

secondary windings of transformer 23, 24 and thyristors 9-12; an eight-step voltage, slightly different from sinusoidal, can be formed at the output of the inverter.

b

The turn-on diagram of the inverter thyristor, which allows forming an eight-stage voltage on the load over the full period, is given in Table. 2

table 2