DE3913675C1 - Commutating arrangement, for frequency converter - has thyristors galvanically connected in pairs and antiparallel to each mains and consumer phase - Google Patents

Abstract

The thyristors are connected in pairs and antiparallel between each user phase and to the poles of a capacitor whereby the user phase to be non-commutating by ignition of a thyristor is connected to one pole of the capacitor and the user phase to be commutating by the ignition of the thyristors is connected to the other pole of the capacitor, so that the current to be non commutating flows across the capacitor and this related to its previous charge condition discharges. ADVANTAGE - Gives user commutating in addition to main commutating depending on user frequency, realised at low hardware cost.

Description

The invention relates to a commutation device for a direct converter, in particular of the type as described in German Patent 35 02 204. It is a natural commutation direct converter for operating a m- phase electrical load, preferably an electrical machine, with the frequency f , on an M- phase ac network of frequency F , where the cycloconverter has a number of 2 · M · m comprises thyristors, which are galvanically connected in pairs and antiparallel with each mains phase and each consumer phase. An essential characteristic of the known cycloconverter is that, apart from commutation-related overlap times, only two mains or consumer phases simultaneously carry current.

Because of the network dependent nature of the natural Commutation done the commutation at fixed times, which exclusively by the mains frequency are determined. Dependent on from the set output frequency and output voltage are beats of the period of Consumer flows unavoidable. For consumers  in the form of electrical machines, in particular asynchronous motors These beats are detrimental on the concentricity properties.

In contrast, the present invention is the Task underlying, in addition to the network commutation a consumer commutation depending on provided by the consumer frequency, which deals with a small amount of hardware let realize.

This object is achieved by the characterizing features of the claim 1 solved. A particularly advantageous control algorithm is characterized in claim 2.

The consumer commutation according to the invention proposal is shown in Figure 1 in conjunction with a direct converter (see Figure 1.1) according to German Patent 35 02 204 in general. Accordingly, the entire disclosure of German Patent 35 02 204 is expressly incorporated by reference as part of the disclosure of this application.

The present invention proposal essentially comprises a commutation capacitor, to whose poles F, K a number of 4 m thyristors T , as shown, are connected.

In another field, namely those of the power link converter technology are commutation circuits known which several capacitors and also additional valves between mains and consumers include; increase through these valves the on-state losses of the inverter.

In the context of the invention, it is sufficient, simple network thyristors since the commutation times sufficiently far apart, so that relatively long seasons are available.

By the invention proposal is the first time Direct current converter created on thyristor basis, which is equipped with a commutation aid, which ensures a low-loss operation of the inverter, there is always only one valve between the network and consumers switched.

By provided in the variant according to claim 2 Possibility of a freewheeling current is a capacitor with a relatively small capacity sufficient with the simultaneous consequence that the entire voltage level  both the commutation and the Inverter is limited to the top.

The particular advantage of the invention proposal shows up in the electric drive technology, in particular when using asynchronous machines.

In addition to Figure 1 of the direct converter described in the German Patent 35 02 204 (Figure 1 there) is shown again in Figure 1.1 matching. Figure 1.1 shows the circuit of the cycloconverter with M- phase network and m- phase consumer. The simultaneously current-carrying thyristor pair T _{X, Y} and T _{x, Y} is shown recognizable.

For a better understanding of the present invention The operation of the proposed commutation is illustrated by the images 2.1 to 2.4. Each of these images shows only a portion of Figure 1, wherein the direct converter example of the commutation of the thyristor T _{x₀, Y} to the thyristor T _{x₁, Y is} shown. The current-carrying thyristors are characterized by a black mark.

Figure 2.1 shows the condition before the commutation. The current flows from the mains phase X via T _{X, y} into the consumer phase y and back from the consumer phase x ₀ via T _{x₀, Y} into the mains phase Y. Due to the preceding commutation process, the capacitor is charged as shown K (+) and F (-).

Figure 2.2 shows the overlapping phase at the beginning of the commutation process. By ignition of the thyristor T _{x₁, Y} , the current flows through both the phase x ₀ and x ₁ back into the network phase Y.

Figure 2.3 shows the by ignition of the thyristors T _{x₀, F} and T _{K, x₁} , according to claim 1, taking place redirecting the current from the consumer phase x ₀ via T _{x₀, F} the capacitor and T _{K, x₁} in the consumer phase x ₁.

The capacitor previously charged with F (-) and K (+) is reloaded to F (+) and K (-) during the commutation process.

Figure 2.3.1 shows the freewheel taking place under inductive load, relatively high currents or small capacitance values of the capacitor, according to claim 2. By additional firing of the thyristor T _{F, y} , the load current after recharging the capacitor from x ₀ now over T _{x₀ , F} and T _F, y flow back into the consumer phase y (freewheeling).

Figure 2.4 shows the situation after commutation from x ₀ to x ₁. The now charged with F (+) and K (-) capacitor is ready for the next consumer commutation process (from y ₀ to y ₁).

Claims (2)

1. commutation device for a direct converter, which comprises a number of 2 · M · m thyristors, which are galvanically connected in pairs and antiparallel with each mains phase and each consumer phase, in particular according to DE-PS 35 02 204, consisting essentially of a number of 4th - M thyristors and a capacitor, characterized in that the thyristors in pairs and antiparallel between each consumer phase. 1 , , m and the poles (K, F) of the capacitor are connected ( Figure 1), wherein the abzukommutierende consumer phase x ₀ or y ₀ by firing the thyristor T _{x₀, F} and T _{F, y₀} with a pole (F) of the capacitor and the commutated consumer phase x ₁ and y ₁ by ignition of the thyristor T _{K, x₁} or T _{y₁, K are} connected to the other pole (K) of the capacitor, so that the abkommutierende current flows through the capacitor and this, based on its previous state of charge, recharges, and where the following definitions apply: M : Number of network phases, with M 2, m : Number of consumer phases, with m 2, x : Positive integer 1 x m for designating the load phase that leads the consumer from the direct converter, y : Positive integer 1 y m for designating the load phase that leads from the direct converter to the load, x ₀, y ₀: Current-carrying consumer phase, which is commuted as a result of the commutation process (consumer phase to be commuted), x ₁, y ₁: Consumer phase, which, as a result of the commutation, takes over the current flowing in x ₀ or y ₀ (consumer phase to be commended), T _{x, F} ; T _{y, F} ; T _{x, K} ; T _{y, K} : Thyristor whose anode is connected to the consumer phase x or y and whose cathode is connected to the capacitor pole F or K , ( Figure 1), T _{K, x} ; T _{K, y} ; T _{F, x} ; T _{F, y} : Thyristor whose anode is connected to the capacitor pole K and F and whose cathode is connected to the consumer phase x and y ( Figure 1). 2. commutation device according to claim 1, characterized in that the abzukommutierende consumer phase x ₀ or y ₀ by additional ignition of the thyristor T _{F, y} or T _{x, F is} connected to the current-carrying in the opposite direction consumer phase y or x , so that a freewheeling current can flow.