SU1677822A1 - Device for converting constant voltage into adjustable alternating voltage - Google Patents

Abstract

The invention relates to power converter technology. The aim of the invention is to increase the efficiency. The device contains two phase-shifted (for the purpose of regulating) one relative to the other in the output current of the inverter 1, 2, each of which is loaded on its own load, which are the same. The goal is achieved using an equalizing transformer 3 with magnetically coupled windings. 3 Il.

Description

The invention relates to converter equipment, more precisely to thyristor frequency converters for electrical technology, and can be used in frequency converters made, for example, according to the scheme of a two-bridge frequency inverter and countercurrent diodes providing phase-impulse power control, as in individual installations of induction heating, and in multibridge converters in centralized power systems.

The aim of the invention is to increase efficiency.

FIG. 1 shows a functional diagram of the device; in fig. 2 and 3 are time diagrams of its operation (with inductive coupling between the windings of the transformer 3 and without it, respectively).

The device contains two phase-shifted relative to each other on the output current of the inverter 1 and 2, the same

the output terminals of the inverter are connected to the beginning of the windings of the leveling transformer 3, the other ends of the said windings form two output terminals for connecting to two identical loads 4 and 5, the other like terminals of inverters 1 and 2 are combined and form the common output of the device.

The device works as follows.

When the control pulses are fed to inverters 1 and 2, they operate in phase, and the currents M, is of loads 4 and 5 are in phase. This corresponds to the consistent inclusion of the windings of the leveling transformer, in which the equivalent nominal load inductance is found by the formula L + 1-3-2 + 2Mz, where L3-1, L3-2 are the own inductances of the windings of the leveling transformer, and Мз is its mutual inductance.

The introduction of a phase shift between the currents of the inductive elements equalizing (L

WITH

about s

00

yu yu

The first transformer 3 (FIG. 3) leads to a change (decrease) in the equivalent inductance and, therefore, in the load impedance for both inverters. As a result, the inverters are unloaded, the operating point is shifted towards the short circuit mode. Upon reaching the magnitude of the phase shift angle p 180 el. hail, according to the output frequency, the currents of the inductive elements of block 3 will be in counter-phase. This will provide the minimum value of the load impedance, since the equivalent inductance for the antiphase (counter) connection of the inductive elements of unit 3 is equal to L La-i + 1h-2-2Mhz. Thus, the change in phase shift between the currents C, Is of the leveling transformer is from 0 to 180 el. hail, leads to a change in the equivalent load and power consumption from a nominal value to zero. Since in the proposed device the introduction of the phase shift angle changes the equivalent load for each inverter in the same direction, namely in the direction of the short circuit, the load of the elements of said inverters is almost uniform in power and. in addition, the same time allowed for the thyristors to restore the control properties. The latter contributes to the stability of the device.

If loads 4 and 5 are inductors, then the electromagnetic coupling

can be installed directly between these inductors.

Accepted in FIG. 2 designation: IHU2 - output voltages of inverters 1, 2; Кз-1, Кз-2 - voltage on the windings of transformer 3 with inductive connection between them (Fig. 2) and without it (Fig. 3).

The proposed device has an efficiency of 5-7% higher than that of the known analogues (this comparison was made for a device at a frequency of 1 kHz, with a power of 2 kW). This is due to the absence of exchange currents between the inverters in this device. In addition, the unevenness in the power load of the thyristors and the elements of the switching circuit of the converter bridges does not exceed 10% of the entire control range.

Claims (1)

The invention of a device for converting a constant voltage into an adjustable variable, containing two phase-shifted relative to each other along the output current of the inverter, and the same output terminals of these inverters are connected to the beginnings of the windings of the leveling transformer, in order to improve the efficiency, The two windings form two output terminals of the device for connecting two identical loads to them, the other inverter terminals of the same name are combined and form a common output for troystva. figure 1 but) h LS fAl 200 1 ", G 1 I) Ј / u 20 ° 100 0 -100 -200 S) Ud, M2 G83 400 200 -200 -400 9 wA-z fft.3 -1C.L -2C -30.1 -40