SU466596A1 - Stand alone voltage inverter - Google Patents

Description

one

In known voltage inverters, at low negative voltages on the thyristors that are turned off, the turn-off time is significantly increased, which reduces the operating frequency range of the inverter.

The purpose of the invention is to improve the energy performance.

This goal is achieved by the fact that the primary windings of the chokes are included in the circuit of each of the reverse diodes.

FIG. 1 shows the scheme of the proposed inverter; in fig. 2 is a magnetization diagram.

FIG. 1, the following designations are given: 1, 2 — a source of direct current; 3, 4 - main thyristors; 5, 6 - reverse current diodes; 7, 8 - commuting thyristors; 9- commuting choke; 10 - switching capacitor; 11 - load; 12 - additional source of electricity; 13, 14 - toroidal transformers; 15, 16 - diodes.

In contrast to the known circuits, reverse current diodes are connected to DC terminals through transformers, the cores of which are made of a material with a rectangular hysteresis loop (Fig. 2). In addition to the working winding included in the reverse-current diode circuit, the transformers have a winding switched on through a diode 15 or 16 to the DC source 12, and a pulse magnetizing winding. Transformers are designed in such a way

that the cores completely reversal magnetize (induction changes from -BS to + Bs) under the action of the voltage of source 12 (on the order of 20-30 volts) for the time required for the thyristor to restore the control

properties.

The scheme works as follows. Suppose the thyristor 3 conducts current. When the thyristor 7 is turned on, the capacitor 10 begins to discharge. When the discharge current of the capacitor 10 exceeds the magnitude of the load current, the excess current is closed through diode 5. When current flows through the working winding of the transformer 13, a voltage equal to the reduced voltage of source 12 is established at its terminals. This voltage is applied to accelerate the recovery control properties of the latter. Under the action of this voltage, the core of the transformer 14 is re-magnetized, the induction is changed from the value of -BS to the value of + Bs. Full remagnetization is completed by the end of the switching. Upon completion of the switching and turning off of the diode 5, the core is returned by the bias circuit to the initial state. Similarly, the process proceeds when the thyristor 4.

Thus, in the proposed inverter, during the switching off of the main / phase thyristors, a negative voltage is applied to them, equal to the dip on the diode 5, 6 and the reduced voltage of the source 12; during the flow of the reactive load current through the reverse current diodes, the counter-e source. d. The circuit of the diode is very short.

Due to this, the low power source 12 is greatly simplified.

The three-phase inverter consists of three similar single-phase inverters connected to the terminals of a constant current source,

source 12 may be common to all phases.

Subject invention

A self-contained voltage inverter containing for each phase two main and two commuting thyristors, between the common points of the serial connection of which the commutating LC-chain is connected,

reverse diodes, and additional saturable chokes in the return diode circuit, the secondary windings of which are connected via a rectifier to a DC source, characterized in that, in order to improve the energy characteristics, the primary windings of these chokes are included in the circuit of each of the reverse diodes.

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Fig 2