SU99555A1 - AC-to-AC converter of another frequency or DC to AC - Google Patents

Description

The subject of the invention is an AC-to-AC converter of another frequency or a direct current to an AC using controlled electric gates.

In connection with the wide development of high-frequency installations for melting, quenching, drying, heating, and other purposes, the task of creating powerful and economical frequency converters of this type is very important.

The difficulty of building such converters at a high frequency (300-500 Hz and above) is due to the fact that electric valves (mercury rectifiers, ignitrons and thyratrons) cannot work in this mode and go out of service after a few hours.

In order to facilitate the work venti. In such converters, achieved by reducing the rate of recovery of the reverse voltage and creating a delay in the appearance of direct voltage at the switching valves, it is proposed to switch on the switch circuit of the said valves.

reactors and valves in parallel are electrical capacitors through which a reverse current flows after coupling, reversal of the corresponding reactor and increasing its inductance at that moment.

In the event that the intrinsic capacity of the shunt valves is sufficient to remagnetise the reactor, only saturable reactors can be used in the converter, without capacitance bypass valves.

The drawing shows a schematic diagram of a multi-phase converter, whose operation, as is well known, proceeds as follows.

When two valve groups are fed to the grids of alternating unlocking voltage, the current flows through one half of the transformer winding and the corresponding valve group. At the same time, in the second half of the transformer winding, a voltage is excited, causing the appearance of additional current flowing through the capacitor C and the burning valves. In this case, the capacitor C is charged and when the second valve ground is unlocked, the discharge circuit is discharged, providing current switching, i.e., extinguishing of the wide shafts of their valves and beyond; kking other gates.

To convert a high frequency, the inductance of the commutating circuit must be small (otherwise, the switching time from one group to the other will be large, which will not allow a high frequency to be obtained). In these words (very fast current decay, very rapid rise of the reverse voltage on the valve due to the negligible inductance of the switching circuit), frequent reverse ignitions can be avoided only if the operating voltage drops sharply against the nominal voltage of this valve. In this mode, the anode is also strongly sprayed.

As a result, the valves after a few hours, and sometimes less than an hour. After an hour, get out of order.

In order to simplify the operating conditions of the valves in the proposed converter, a large amount of L, connected reactors L connected in the circuit of the switch valve commutation, is attached. The capacitors C | are connected in parallel with the latter.

When a current flows through the valves of the reactor L is saturated, its inductance is small and it does not hinder the fast switching of the current. When the flow of direct current through the reactor L and the capacitor Ci, connected in parallel to the valves, stops, a reverse current flows. This entails a dramatic increase in reactor irradiation, which reduces the rate of increase in the reverse voltage and the danger of reverse sailing. Priming. The use of saturable reactors is particularly effective in high frequency converters, in which the absence of these reactors makes it extremely difficult to prevent the valve from reversing.

The use of saturable reactors makes it possible to arbitrarily reduce not only the rate of increase.

but also the amplitude of the reverse voltage, which makes it possible to completely prevent the danger of reverse charging.

In any case of an ion current transducer into alternating current, or a current of one frequency into a current of another frequency, the reverse voltage affects the valve only part of the period, after which the direct voltage begins to act, causing the danger of a valve opening in the forward direction. In the presence of a saturating reactor, after restoring reverse flow, the reactor turns out to be reversible in a reverse direction, and the capacitors connected in parallel to the valves are recharged by reverse voltage.

The reverse recharge of this capacity with an increase in direct voltage also occurs through the reactor, the inductance of which is high until it is saturated, which contributes to a delay in the occurrence of direct voltage on the valve and allows an increase in the time allowed to restore the correctness of the valve. .

In case the installation's own capacity, the shunt valve, is sufficient to remagnetise the reagistor,. limited only by the inclusion of reactors in the switching circuit, excluding capacitors C and shunt valves from the circuit.

Subject invention

Claims (2)

1. AC-to-AC converter of another frequency or DC to AC using controlled electric valves, characterized in that, in order to facilitate the operation of the valves by reducing the recovery rate of the reverse voltage and creating a delay in the appearance of direct voltage In the switching circuit of the valves, saturable reactors are connected and, parallel to the valves, electrical capacitors are connected, through which, after the switching of the leakage. T current, remagnetization conductive suitable reactor and raising at this point its inductance. 2. Modification of the converter according to claim 1, of which is UJ, e e with the fact that only saturated reactors are used - without shunt capacitor valves - in case the plant's own capacity, bypassing the valves, is sufficient to remagnetize the reactor. Priority under item 1 9 October 1950, by If. 2 January 20, 1951