DE975001C - Arrangement for the operation of power converters in which a circuit interruption occurs mechanically - Google Patents

Description

(WiGBl. P. 175)

ISSUED JUNE 29, 1961

TO (JGTHEK

DES GERMAN «

PATEHTVlSiTES

A68po VIIIb12id *

has been named as the inventor

Addendum to patent 974 690

(Ges. Of 15.7.1951)

The subject of the main patent is an arrangement for the operation of converters, in which the circuit is interrupted mechanically and the converter is circuit-wise divided into η phase-shifted partial converters with at least two phases working in cyclical order, of which at most one phase carries current and where η at least is equal to 2, and inductors or transformers are connected between the phase voltages of the partial converters; The characteristic is that these reactors or transformers are dimensioned and magnetically designed in such a way and a voltage with such a quality in terms of frequency and waveform is present at their terminals that not only in the vicinity of idle, but in certain time particles in the entire load range Current is distributed to η current paths, and that in other time particles the current is taken over by less than η current paths. According to a further proposal, the alternating current required by the choke coil or the transformer and superimposed on the load current of each converter element changes automatically with the load current at least over a part of the load range. Included

109 605/9

if the choke coil or the transformer has an unwound leg apart from the wound legs Leg on and is dimensioned such that its inductance is reduced so much with increasing load current is that the magnetizing current remains the same as the direct current. It is beneficial for that magnetic paths of the inductor or the transformer toroidal cores made of high quality ferromagnetic Material, e.g. B. silicon or iron-nickel alloy to be provided.

As has now been already shown, there is at a 30 ⁰ delayed contact time of the choke coil and the transformer, the voltage U _s, which is in Fig. Ι the drawing shown. This curve rises linearly between t ' and t " and between t" and t'" . T ', t" and t'" are the times of the contact change. In FIG. 2, for which the same time relationships as in FIG exist, the corresponding portions are the mean flux flow shown in the two ring cores in a two-three-phase converter sections power converter having a main transformer. the portion of the curve? 7 _S between t 'and t "corresponds to the flux flow, wherein the near f the core carrying the flux _{2 is} almost desaturated and in the vicinity of t " the core carrying the flux Φ _{1 is} almost desaturated. With a low load by the operating direct current, the flux curve actually corresponds to this curve. With increasing load current, however, Ug occurs in the voltage curve an indentation which, with larger currents, finally covers the area α & cd. This indentation comes from a partial breakdown of the transformer voltage, its depth due to its stray voltage and the speed at which the currents I _gl and I _g2 are replaced. I _gl represents the current profile in one partial current rectifier, I _g2 in the other partial current converter. Both parts of the curve are also entered in FIG. As soon as both iron rings are saturated during the current reversal, the choke coil acts like a short circuit on the anode voltages. The result is a rapid increase in the current in one converter section, while the current in the other converter section decreases at the same but opposite speed.

If one now _{follows the course of the flux for the notched voltage curve U 5} , it can be seen that if this notch goes to the zero line, the flux cannot increase during this time. As a result, the flow course forms a stage b '. .. c ', ie during this time the flow remains constant. The corresponding sections of curve Φ ₅ move up and down accordingly and thus form the flow courses Φ _ί and Φ ₂ . This approach applies provided that the choke coil has no stray voltage and that its iron sheets show no further increase in induction B after the bend in the magnetization curve. With an increase in the last sizes, the mentioned step b '... c' is no longer horizontal, but takes an inclined position. The stray voltage of the choke coil acts in the same way as the stray voltage of the transformer, reducing the flux-forming voltage. The two partial flow curves Φ ₁ and Φ ₂ now show the flow course in the two partial rings. The middle line, as shown in the figure, corresponds to the saturation state, while the desaturated state is marked for Φ ₁ with an overlying line, for Φ ₂ with a line below. It can be seen from this that the flux formation is partly carried by one iron core and partly by the other iron core. The step in the flow curve reduces the maximum flow achieved by the amount Va Φ _η in both toroidal cores. The consequence of this is that the increase in flux that takes place until the state of saturation is reached is reduced. As a result, the current reversal advances in time, for example by the amount 6 '... 0, as shown in the drawing. If this property did not result in the reversal of the current being brought forward with increasing current, this would only begin at time 0 . Since the current reversal time t _n ' increases proportionally with the increasing load current, it should take at most a time that corresponds to the distance 0 until the contact changeover. As a result of the advance of the current reversal, however, a considerably larger amount is available, since the current reversal time extends to a larger part before point 0 (distance b '.,. 0) and a smaller part (distance 0 ... c') . The distance 0 ... c ' can theoretically extend until the contact change, the distance b' ... 0 advances accordingly. This property makes the circuit heavily overloadable, since there is no need to fear that the contact will have an impermissibly high current, even if it is heavily overloaded.

When dimensioning the reactor or the transformer, one must ensure that that the described effect occurs whenever possible. For this it is necessary that the used Iron cores the induction increases little after the kink in the magnetization curve and that, on the other hand, the leakage inductance of the choke coil and main transformer are sufficiently large, so that this tension notch is achieved. One can also see the stray voltage of the choke coil dimensioned very small and then the main transformer a corresponding larger spread give. This has the advantage that transformers with a larger short-circuit voltage are used can use in order to avoid such large short-circuit currents in the event of incorrect switching of the contacts. The arrangement of toroidal cores in the choke coil allows the leakage voltage to be reduced in the ver iao Keep ratio to that of the main transformer very small, so that this condition is also practical can be easily met.

In practical executions of the above. Switching occurs in the vicinity of the contact change, a pause from 5 to 15 ⁰ , which, however, occurs at the above

Executions fundamentally do not change anything. By means of the previously proposed capacitors parallel to the contacts, the connection of the anode voltage to the side of the choke coil of the releasing contact is maintained even after the contact is interrupted, so that the linearity of the voltage curve U ₃ is also approximately maintained. If necessary, this flow course is also approximately enforced for the purpose of an interruption of positive currents at the moment of the interruption of contact.

Claims (2)

PATENT CLAIMS: ι. Arrangement for the operation of converters in which a circuit interruption takes place by mechanical means, according to patent 974 690, characterized in that the stray voltage of the main transformer and advantageously also of the choke coil is selected to be large in relation to the increase in the magnetization curve of the sheet metal used after the kink, so a temporal advance of the individual current blocks occurs with increasing load current. 2. Arrangement according to claim 1, characterized in that that the stray voltage of the main transformer in relation to the stray voltage and the rise in the magnetization curve of the sheet metal used in the choke coil after the kink is chosen large, so that on the one hand a temporal advance of the individual Current blocks is achieved with increasing load and on the other hand the short-circuit currents of the transformer can be reduced in the event of a faulty connection. 1 sheet of drawings © 109 605/9 6.61