DE3546614C2 - Transformer circuit - Google Patents

Abstract

Published without abstract.

Description

The invention relates to a transformer circuit according to the preamble of claim 1.

Such transformer circuits are everywhere Ver where an output from the voltage source is Ver Supply voltage of a load, at least temporarily not unchanged but only with changed amplitude can be led.

A known transformer circuit of this kind, as they For example, the CH-PS 1 18 811 can be removed, points an actuator on which a transformer with a with the load in series first winding and little Stens another winding comprises whose Windungsver ratio to the first winding is greater than 1. Furthermore are Switch provided with their help by applying Control AC voltages to the at least one more Winding the actuator in at least two different Switching states can be brought:  

In a first switching state, a voltage Δ U ₁ is induced in the first winding of the transformer, which adds by appropriate choice of the winding sense of the other winding with respect to the first winding to the input voltage, so that applies to the ver compared to the input voltage ver changed output voltage U _A :

U _A = U _E + Δ U ₁. (1)

The relative size of Δ U ₁ with respect to the control voltage U _S by the turns ratio w ₁ / w _{w of} the first winding of the transformer for further winding is given:

The turns ratio w ₁ / w _w is less than 1.

In a second switching state, a control voltage is applied to the further winding with such a winding sense that the thus induced in the first winding further voltage drop Δ U ₂ of the input voltage sub trahiert. In this case, the following applies to the output voltage:

U _A = U _E - Δ U ₂ (3)

In this case, Δ U ₂ depends on the control voltage U _S also according to the above equation (2).

This known arrangement can also be brought into a third switching state, in which the further winding is short-circuited, in order to achieve that no voltage is induced in the first winding in series with the load, and thus the output voltage U _{A of} the actuating unit in is approximately equal to the input voltage U _E.

This type of generation of the three different Schaltzu Stands, however, has the serious disadvantage that the Control signals for the different switches from each other generated separately and thus secured against each other need that never all switches that the further winding attach to one of the control voltages, can be closed, when the switch or switches are closed, with their Help the other winding to generate the third Switching state is shorted. The required for this The considerable technical complexity is considerable and can never completely exclude that it to damage or even destruction of the actuator or the entire transformer circuit comes because on reason of a switching error, the above-mentioned switching paths closed at the same time. The only way out, the is offered here according to the state of the art, is the Use of overcurrent fuses, however, too an increased amount of components mean and also by their operation the operation of the entire arrangement interrupt more or less long.

In contrast, the invention has the object, a Transformer circuit of the type mentioned so on zubilden that with the lowest possible schstestech niche effort is ensured that it when switching a stage of the transformer circuit from the first or second in the third switching state or when switching from the third in one of the other two switching states not by the failure of sensor, logic or Control circuits can come to dangerous short circuits.

To solve this problem, the invention provides that the transformer circuit comprises at least one stage, which consists of at least two actuators, the like connected in series with each other, that the output AC voltage of the front actuator the input is the AC voltage of the rear actuator, and that the two actuators thus a set of actuators form that the winding ratios of the first windings are matched to the other windings so that the output voltage of the actuator units equal the input voltage of the actuator pair is when the one of the actuators on their input voltage one induced voltage additive and the other actuator to their input voltage an induced voltage sub attractively imprinted.

According to the invention, therefore, a stage of the transformer circuit is formed by two actuators, which are not only connected in series with each other, but also formed as an actuator units pair. This is to be understood as meaning that the two actuators, regardless of whether they are constructed with one or two further windings, only those switches which are required to bring each of them selectively in the first or second switching state. By contrast, no switches are provided, with the help of which the further winding or one of the two further windings could be short-circuited. Thus, it is not possible to bring one of these actuators alone in the third switching state, in which the output voltage is equal to the input voltage. Instead, the Windungsver ratios of the first two windings of the two transfor mators to the associated further windings in two actuators are coordinated such that at a given input voltage U _EP for the actuator units the following equations apply:

U _AP ₁ = U _EP + Δ U _P , (4)

U _AP ₂ = U _EP - Δ U _P and (5)

U _AP ₃ = U _EP . (6)

U _AP ₁ is the output voltage of the actuator unit pair, which results when both actuators are in the first switching state, so that their two positive impressed voltage changes + Δ U and + Δ U ' to a positive pair voltage change + Δ U _{Add P} U _AP ₂ is the corresponding output voltage when both actuating units in the second switching state, so that two negative their on embossed voltage change - add Δ U _P - Δ U and - Δ U 'to a ne gativen pair of voltage variation. The Windungs ratios can be chosen such that the pair voltage change Δ U _{P has} in both cases in about the same absolute amount, so the two output voltages to the input voltage are symmetrical.

It is essential that the Windungsverhältnisse are also chosen such that in a third switching state combination in which z. B. the first actuator in the first and the second actuator in the second Schaltzu was, compensate for the effects of the two actuators approximately, so that the output from the actuator pair output voltage U _AP ₃ equal to the input voltage U _EP supplied.

This third switching state combination thus corresponds in their effect on the output voltage of the pair third switching state of a single actuator, whose further winding is shorted.

For example, if such an entity pair out the first switching state combination in which Both actuators are in the first switching state the, in the third switching state combination Umgeschal It is only necessary to have one of the two actuators from the first to the second Transfer switching state. This can generally be there done by that a switch or switch pair opened and another switch or switch pair is closed. The control of this switch or this Switch pairs can be done with a single control signal, the one switch or switch pair directly and the other switch or switch pair, for example via an inverter is supplied. Because there is no additional  Switches, with the help of the further winding or one of the other windings can be short-circuited, there is no danger that when closing a sol switch the switch path with which the relevant another winding is applied to a control voltage, nor not open. Thus there is no danger of it to corresponding short circuits with the result the risk of damage or destruction of the transformer circuit is coming.

Although according to the invention instead of a large trans formators two small transformers with the corresponding ones Windings used, but this is not a disadvantage, because each of the two small transformers only half Process the power of the corresponding large transformer got to. This has the consequence that also the size of the core and the cross section of the wires used for the windings reduced accordingly, so that here in total no additional need for material arises.

In addition, the arrangement according to the invention offers the following advantages:
It has a much higher immunity to interference, because then, if in one stage, for example, the control fails for a transformer, not the entire, but only half the control range of this stage is lost, since with the remaining transformer still half the step voltage change additive or subtractive to the input voltage of the pair can be impressed.

Furthermore, the electronic switches, with their Help the other windings are switched, for a much lower switching capacity to be designed.  

In addition, there is also the advantage that Warehousing is simplified, because for one and the same transformer circuit more equal transformers can be used as this is the case when for every stage a single transformer is used different from the other stage transformers is.

Although it is known from GB-PS 9 61 289, to achieve a greater number of different output voltages several switchable transformer assemblies in series to switch. However, these transformer arrangements are differently constructed than the verwen in the subject invention Deten actuators, and the inventive training of actuators pairs is by this document neither anticipated nor suggested.

The two switching states of each actuator can each realized by means of the same further winding be with the help of the switch either to the one or to the other control voltage can be placed.  

Alternatively, however, two further windings may be provided, to which a control voltage is alternately applied, so that the actuating unit with the exception of short switching or transition times either in the first switching state, in which only a control voltage is applied to the first further winding, or in the second switching state, in which only at the second further winding, a control voltage is applied. Preferably, the number of turns, the control voltages and the sense of winding of the two white windings with respect to the first winding are so selected that the amplitudes of the two inducible voltages Δ U ₁ and Δ U ₂ are approximately equal, but the two inducible voltages with opposite sign to the input voltage U _{E are} imprint bar. Thus applies to the output voltage U _A in the first switching state

U _A ₁ = U _E + Δ U ₁ (7)

in the second switching state

U _A ₂ = U _E - Δ U ₂. (8th)

Although the control voltages can be generated in various ways and applied to the other windings. Preferably, however, in the first Schaltzu was the first further winding with the help of the switch directly galvanically connected to the input voltage U _{E of} the actuator, while in the second switching state, the second further winding is directly connected galvanic nically with the output voltage U _{A of} the actuator, so that one obtains an autotransformer arrangement in both switching states.

Even if the second switching state is realized in that a single further winding is alternatively applied to two different control voltages, the input voltage U _E and the output voltage U _{A of} the control unit can be used as control voltages to which the further winding under consideration of the winding sense with the help the switch can be galvanically connected directly so that the one induced voltage Δ U ₁ according to the above equation (7) adds to the input voltage and subtracts the other induced voltage Δ U ₂ according to the above equation (8) from the input voltage U _E. However, these two inducible voltages Δ U ₁ and Δ U ₂ can not be independently selected who the. They are rather according to the equations

and

linked together when w ₁ the number of turns of the first winding and w _{w is} the number of turns of the further winding of the transformer.

In a preferred embodiment, however, two more windings of the transformer are provided, one of which finally finds use as an adding winding and the other exclusively as a subtractive winding use. Thus, there are an additive induced voltage + Δ U ₁ and a subtractive inductive voltage - Δ U ₂ available, which are independent of each other, since for each of the two other windings a separate number of turns w _w ₁ and w _w ₂ can be selected. For the impressed induced voltages, the equations apply:

and

If you choose w _w ₁ and w _w ₂, for example, so that

w _w ₁ = w ₁ + w _w ₂

applies, so can the input voltage U _E exactly symmetrical output voltages U _A + and U _A - achieve. Alternatively, but also desired if the from the equations (7) and (8) apparent asymmetry between + Δ U ₁ and - Δ U ₂ be further enhanced.

In addition, this embodiment allows one each Connect the end of the two further windings firmly  and only the other end with the help of a switch either electrically conductive to the input or off To put voltage or separate from this. It So instead of four only two switches per actuator are needed.

As already mentioned, the inventive Trans formatorschaltung is especially advantageous if the voltages to be induced + Δ U ₁ and - Δ U ₂ account for only a relatively small percentage of the input voltage U _E. The turns ratios w ₁ / w _w or w ₁ / w _w ₁ and w ₁ / w _w ₂ are therefore generally less than 1 and are preferably in the range from 1: 3 to 1: 200.

To not overload the transformer are special measures are provided that are safe put that only for one of the several further Wick The associated switch or switches is closed are. For the preferred embodiment with two white windings, of which one fixed as adding Winding and the other fixed as a subtractive winding wired, it means that the two switches are not operated overlapping.

To simultaneously close the relevant switch impossible to do is the switching state of each Switch with the help of an associated sensor unit monitored and a closing order for one so far open switch suppressed by a blocking circuit, if the output signal of the sensor unit of the other Switch indicates that one of these other switches is still closed is. A corresponding protection circuit can  also for the embodiments of Units where more than two switches are provided to one more one Winding or several other windings in the ver to bring different switching states.

It is desirable that when switching from one switching state to the other, the output voltage U _{A of} the control unit as fast as possible and "smooth", ie without strong fluctuations in the amplitude absolute value of the AC output voltage up or down from their old to the new amplitude value passes.

So when switching from a switching state in the other as low energy losses and possible small switching points arise, it is necessary to Switch at certain phase angles or in certain Phase angle ranges of magnetic flux, the the first winding of the transformer interspersed, too open or close. These phase angles or phases angular ranges are chosen so that this magnetic flux through the opening or closing little changes.

As switches are preferably used triacs, the after a zero crossing of the current flowing through it go into a locked state, which is the "open" Switching state of a switch corresponds. For opening It is sufficient for a hitherto closed triac switch So, after a zero crossing of this switch  flowing current re-ignite the triac to prevent at the next half-wave.

In the immediate over from the first to the second switching state or to swept, although the triac switch before preferably at a zero crossing of they flow through the current is open, but can each be closed Switch not simultaneously with the opening of the previously closed switch are actuated when the Be Condition of the smallest possible change of the magnet flow is to be respected.

The criterion for the times to close the Switch is for the transition from the second to the first Switching state (generation of an additive induced Tension) other than that for the transition from first in the second switching state (generating a subtractive induced voltage). In the first case is it is expedient to close the switch (s) when the magnetic flux has a zero crossing while in the second case, the switch or switches closed when the absolute value of the magnetic flux is on Maximum goes through. Because in both cases the optimal Switching time against the two phases just mentioned angle as a function of the size of the load current something can be shifted, the closing process must ever because in one of the mentioned phase angles surrounding Phase angle range done. To this closing criterion for the switches to be able to comply is a sensor device for detecting the phases History of the magnetic flux in the first winding before seen. Preferably, this sensor device is a  Sensor winding of the transformer whose output chip With a shift of 90 ° the phase angle of the Magnetic flux reproduces. The output voltage is the supplied electronic switch control, the result according to the above criteria, automatically correct switching times determined.

As already mentioned, results in periods, in which none of the other windings to the input voltage or to the output voltage of the actuator connected to the first winding of the transfor mators a comparatively high voltage drop, whose Size depends on the load current. However, this requires Voltage drop after the replacement of a previously connected another winding a whole Row of alternating voltage periods, until it turns to its has built up full size. Therefore, if the direct Switching from the first to the second switching state (or vice versa) after opening the or so far closed NEN switch or the previously open switch inside half of a few alternating voltage periods closed be, so the break in the output voltage, due to the above-mentioned increased voltage drop at the first winding occurs, so small that he himself does not adversely affect. It is preferably a electronic switch control uses the example example may include a microprocessor to the switching operations as quickly as possible.

However, if one wants this break in the output voltage of Completely avoid setting unit, without further measure took place during the periods in which the Um switch from one switching state to the other going to none of the other windings Control voltage is applied, so you can on  Transformer provide a short-circuit winding whose Ends by closing a controllable switch can be connected directly to each other. This Short circuit switch is also from the switch control operated. He is usually open and is only at the transition from a switching state in the other closed for a short time. This closing he follows at the same time as opening the one or the other closed switch of the further winding; the short Close switch remains closed until the or the previously open switch the other Wick be closed, and at the same time as opened again this closing process.

Preferably, a triac as a switch for the short used in any case Zero crossing of the current flowing through it problem can be opened.

If one wants to provide more than three different load voltages successively for a given supply voltage U _V , it is advantageous to provide a transformer circuit in which two or more stages are connected in series with one another in such a way that the supply voltage U _V at the first stage As input voltage U _E is applied, the output voltage U _{A of} this first stage is applied as input voltage U _E to the second stage, etc. and that the output voltage of the last stage of the load as a load voltage U _{L is} supplied. In this case, the first windings of the transformers of all stages are then in line with each other and with the load in series from the voltage source.

In general, for a pair of actuaries remains the fourth switching state combination unused, in which the first actuator in the second switching state and the second actuator is in the first switching state. The above information can be in the following Summarize Table 1:

Table 1

In order to be able to cover a larger range of output voltage values in small voltage steps, it is advantageous to have a plurality of stages which can either consist of individual actuator units with short-circuit capability for at least one of the further windings or of the actuator unit pairs described above Types can be mixed), serially in succession to scarf th and the voltage differences + Δ U ₁,. , ., ± Δ U _n , which can generate n of such stages, to choose different from each other. It is particularly advantageous if the percentages that result when dividing each of these voltage differences by the supply voltage divided by 100 are in the ratio of integer powers of three. So applies for the smallest, by one of the stages producible voltage difference ± Δ U _min :

Thus, the voltage differences of the other stages are chosen such that they are approximately equal to ± 3 A %, ± 9 A %, etc. of the supply voltage U _V.

For example, if three stages are connected in series in a transformer circuit, and only the three above-mentioned switching states or switching state combinations are used for each stage, twenty-seven combinations of switching states are possible for the entire transformer circuit, one of which voltage supplied by the voltage source with nearly unchanged amplitude to the load, while thirteen combinations increase the amplitude of the supply voltage by an integral multiple of A % and thirteen combinations lower this amplitude by an integral multiple of A %. This is shown in more detail in Table 2 Darge.

In this table, the sequence number n of the respective combination of switching states is reproduced in the left-hand column, wherein the superscript "+" or "-" indicates whether it is a combination which leads to an enlargement ("+ ") leads to the amplitude of the supply voltage or a combination that lowers the supply voltage (" - ").

Table 2

In the middle column, a "+" means that in the relevant stage, the one or both actuators of a pair are in the first switching state, so that the amplitude of the supply voltage by 9 A %, 3 A % or A % is increased, while a "-" means a corresponding reduction and "0" symbolizes the third switching state of an individual actuating unit or the switching state combination 3 (see Table 1) of the relevant actuator unit pair, in which the amplitude of the input changes voltage is passed unchanged. In the right column, the achievable by the respective combination of the switching states of all stages total changes in amplitude are reproduced. Only rounded values are given which do not take into account that the input voltage of the stages arranged closer to the load may change depending on the switching state of the preceding stages.

It can be seen that the amplitude change with the aid of such a transformer circuit takes place in discrete steps, wherein the step size from one switching state combination to the next is always approximately equal to A % of the respective supply voltage.

As an alternative to the arrangement just described, only two switching state combinations of each actuator pair can be used, for example, the switching state combination 0, in which the output voltage is equal to the input voltage, and the combination "-", in which the output voltage is n · A % is lower than the input voltage, where n takes a different integer value for each actuator unit pair. For this case of application, it is possible to construct the actuator units pairs so that they can take only these two Schaltzu stands combinations. This can be done in such a way that z. B. the front actuator of each pair has a hardwired, non-switchable further winding, the permanent example, a negatively applied voltage - (n / 2) · A % induced, while the second actuator has an adding and subtracting another winding, the Alternatively, they can be switched to induce either a voltage of + (n / 2) * A % or - (n / 2) * A %, which in combination with the induced voltage - (n / 2) * A % of the front actuator either a voltage change 0 or - n · A % results. Correspondingly, actuator unit pairs can also be provided which can only assume the two switching state combinations 0 and + n * A %.

In all these cases, the change in the output voltage of the entire transformer circuit with respect to the input voltage does not occur after the in Fig. 2 given again ternary code, but according to a binary code. Although here more coverage unit pairs than the ternary code are required to cover the same voltage change range; However, there are applications in which anyway the input voltage is to be changed starting from an overall change 0 in only one direction and / or the voltage change range is not large. Then the advantage of a purely binary control may outweigh the increased demand for actuators.

Regardless of how many steps behind be switched to each other and whether a binary or a Ternary or another code is used, it is a salient feature of such a structure Transformer circuit that they have a gradual or digital influence also from very great achievements allowed. Unlike analog work It has an extremely high level of systems Control or control speed. The he each aimed accuracy depends essentially only on the number of actuators or stages used from.

The typical and preferred use of a two, three or more stages existing inventive transformer circuit is ever but not in that starting from a fixed, from a voltage source derived supply voltage nine, twenty-seven or more output voltages one after the other should be selectively generated.

Rather, in a particularly preferred application, the use of such a transformer circuit as voltage stabilizer and / or voltage regulator seen before. This means that as the setpoint S _L for the voltage supplied to the load, either the nominal value of the supply voltage U _V delivered by the voltage source or another voltage value can be selected. However, such other setpoint must be within the range of change of the transformer circuit according to the invention. If it is very close to the limit of this range of change, a control of the load voltage U _{L is} possible only in the case of deviations from the setpoint value S _L in one direction. But this is completely sufficient in cases where deviations in the other direction do not occur.

In the following, the application as a symmetrical voltage regulator is explained in more detail, with the help of which prevents the amplitude of the load voltage supplied to a load of a predetermined setpoint S _L by more than ± δ % deviates, equal to the nominal value of the supply voltage U _V is, which can vary in a much larger range, for example by a maximum of ± Δ % of the nominal value.

For this purpose, such a voltage regulator comprises, in addition to a transformer circuit with accordingly many stages, a sensor arrangement which measures the amplitude of the supply voltage and / or the amplitude of the load voltage, a comparator arrangement which compares the one or more reference signals with one or more reference values Deviations corresponding differential signals generated, as well as a switch control, which compares these Differenzsig signals, for example, with a permanently programmed table of difference signal values. The switch controller determines that combination n ⁺ or n of the sem comparison ^- of switching states (see Table 2), which is a compensation of the occurred deviate the supply voltage from the nominal value monitoring is required so that the load voltage within the predetermined range S _L ± δ% remains.

It is now assumed that the amplitude of the supply voltage initially corresponds to the nominal value and thus also the setpoint S _L , but then deviates in the course of time from this nominal value increasingly, for example upwards: In this case, the switch control of the first existing Switching state combination n = 0 (see Table 2), in which the load voltage U _{L is} equal to the supply voltage U _V , in time for the switching state combi nation n = 1 ^- on further increase to the combination n = 2 ^- etc. go over. As a result, a corresponding integer multiple of A % is subtracted from the supply voltage and thus the load voltage in the desired ge range S _L ± δ % held.

_{(+1 n) /} - - at steadily increasing positive deviation of the transition from the n takes place ^- th combination for the (n +1) ^- th combination each at a specific switching threshold SW _n, ie a fixed amplitude value of the supply voltage. Takes the positive deviation as the steadily from, it takes place at about the same switching threshold in the reverse direction, the transition from the (n + 1) ^- th combination to the n ^- th combination of switching states. It is advantageous to separate the two last-mentioned switching thresholds by a small voltage difference from each other. By thus obtained "hysteresis" too frequent a switching cycle in the cases verhin changed, in which the supply voltage U _V for a long time has a value which is equal to a switching threshold, and slightly fluctuates by this value.

The same applies to negative deviations of the amplitude of the supply voltage from the nominal value only that here the switching thresholds with SW _{n + / (n +1) +} be distinguished, because in this case with increasing deviation down from the additive imprint of n times the minimum amplitude change A % to the additive imprint of the (n +1) -fold of A % must be gone over in order to achieve the desired constancy of the amplitude of the load voltage.

Each transition from a combination of Schaltzu states to an adjacent combination, the amplitude of the load voltage changes abruptly by about A %. Preferably, the switching thresholds are set so that when the amplitude of the supply voltage passes through the value of the relevant switching threshold without sudden change, the amplitude _values U _Lvor and U _{Lnach are} symmetrical to the desired value. In this case, U _{Lvor is} the amplitude of the load voltage before the switching operation and U _Lnach the amplitude of the load voltage after the switching operation. It should therefore apply with the best possible approximation:

| S _L - U _Lvor | = | S _L - U _Lnach | (13)

continues to apply

The percent value A is constant, but is not related to the setpoint S _L , but relative to the amplitude of the input voltage of the respective stage. Thus, the size of U _Lvor and U _Lnach depends on which combination of switching states a transition to an adjacent combination occurs.

The above equation (13) can be maintained in any case by suitably selecting the switching thresholds SW . It is also possible according to the invention to ensure, by an appropriate choice of A , that U _Lvor and U _{Lnach lie} within the amplitude range predetermined by the desired control accuracy S _L ± δ%, the percentage being based on the desired value S _L = 100% is.

When determining the value of A is to take into account that on the one hand A should be as large as possible, as little actuators to cover a given range of fluctuation Δ are required, but that on the other hand A may not be too large, because otherwise the desired Regelgenauig speed δ can not be met. In the present invention, A is preferably selected to be between 1.6 x δ and 1.8 x δ .

It should be noted again that the switching thresholds can be used regardless of whether the circuit operates as a voltage stabilizer or as a voltage regulator, that is, whether the load voltage U _{L is maintained} at a setpoint S _L, which is equal to the nominal value of the output from the voltage source Supply voltage is or at a setpoint that differs from this nominal value.

Also, the use of these switching thresholds is inde pendent of whether the Ver sorgungsspannung or the load voltage is measured with the probe assembly. In the first case, the difference of the above switching thresholds to the setpoint S _{L may be included} directly in the table used by the scarf tersteuerung, with wel cher the difference signal supplied by the comparator is similar. In the second case, the switch control must determine from the approximation of the amplitude of the load voltage to one of the values U _Lvor and U _Lnach and / or the knowledge of the currently valid combination of switching states to which switching threshold, the supply voltage is just approaching, and which switching therefore made must become.

Another possibility is that the measuring sensor arrangement measures the amplitude of the AC voltages in front of and behind the transformer circuit. It will then be the changes of both the versor supply voltage U _V and the load voltage U _L he summarizes and evaluated so that the switches of Stellein units are controlled so as to give the best possible constancy of the amplitude of the load voltage supplied.

Another possibility, at the output of an actuator successively more than three different output voltages to provide available, is to the at least one further winding by means of switches alternatively one of several control voltages U _S ₁,. , , U _S ₂ _q increase, at least partially differ in their Ampli tude from each other. Where q is any integer greater than 1.

To generate this control voltage U _S ₁,. , ., U _S ₂ _q is preferably an AC voltage source use Ver, which has a plurality of taps, between which different tap voltages U _X ₁,. , ., U _{Xp are} constantly available and can be tapped. p is also an integer greater than 1 and preferably less than q . With the help of switches, these tap voltages can be added either individually or in groups as control voltages are applied to the further winding of the transformer.

It is an essential aspect of the invention to provide a transformer circuit which allows a digital change of the voltage applied to a load and thus also the power delivered to the load in a predeterminable range of change + Δ U _max . In special cases, the range of change can only be positive or negative; ie, only the additive or only the subtractive imprint of induced voltages Δ U on the input or supply voltage can be required. In the following, however, the general case of changing to zero (input voltage equal to output voltage) symmetric change range ± Δ U _{max is} explained.

Under a digital change in the output voltage in this range ± Δ U _max is understood to mean that both the positive and to the negative side has a smallest aufprägbare voltage change + Δ U _min and - are Δ U _min, and that of the positive part of amendments range q positively aufprägbare voltages + Δ U _ν (ν = 1,, q...) and in the negative part of the change area q negative aufprägbare voltage - Δ U _ν are available (ν = 1,, q...) where:

+ Δ U _ν = ν · (+ Δ U _min)

and

- Δ U _ν = ν · (- Δ U _min ).

That is., That both in the positive and in the negative part of the variation range, any aufprägbare voltage ± Δ U _ν is an integer multiple of the supplied hearing smallest aufprägbaren voltage ± Δ U _min, and in that ν accept all integers between 1 and q can. The maximum possible inducible voltage in each direction is at the same time the limit of the range of change:

± q Δ U _min = ± Δ U _max .

It is seen that the range of variation both wide by selecting the smallest change ± Δ U _min, and thus the step as well as by choice of the number q of the steps may be varied. An increase in the step size, however, leads to a reduction in accuracy, with the z. B. when using the Trans formatorschaltung invention as a control device, the load voltage U _L can be kept constant at a predetermined value. On the other hand, an increase of q means an increase in the technical complexity. It must therefore be taken in the determination of the sizes q and ± Δ U _min matched to the particular application optimization.

Preferably, the amplitudes of + Δ U _min and - Δ U _{min are} at least approximately equal, so that therefore applies to the other inducible voltages, at least approximately:

| + Δ U _ν | = | - Δ U _ν |.

In a similar way are the other to the other Winding to be applied control voltagesU _{S ν} according to the Digitally structured invention, d. H. there is a smallest control voltageU _Smin , which are to imprint the smallest induced voltageΔ U _min  leads, and the remaining control voltages are integer multiples this smallest control voltage:

U _{S ν} = ν · U _Smin ,

where ν again goes through all values from 1 to q . To be able to cover the above-mentioned symmetrical variation range of ± Δ U _max 2 q steps, just need q control voltages U _S will _ν provided because each tapped from the AC power source voltage can be so applied in two different ways to the further winding by means of the switch can that in one of the two cases, the winding sense of the other winding with respect to the first winding of the transformer to the winding sense in the other case is just opposite. Thereby, the induced voltage U Δ _ν is then in a case additive and in the other case subtractively impressed on the input voltage of the actuator. Again, it is again possible to interrupt the circuit of the other winding to limit the load current by the resulting throttling effect of the first winding.

To generate the q control voltage U _{S ν} it is inven tion not required to provide q + taps at the AC voltage source so that between each immediately adjacent taps one of the smallest control voltage U _Smin corresponding tap voltage U _Xmin drops.

Rather, the amplitudes of the tap voltages are classified according to a suitable code so that at minimum number of taps (and thus minimum number of switches) all required control voltages U _{S ν can be composed} by additive combination of multiple tap voltages, unless they are directly one correspond to the voltages available between two adjacent taps. So that the smallest control voltage U _Smin is available, at least one pair of adjacent taps must be provided, between which a tap voltage U _Xmin = U _Smin drops. Between the remaining pairs of adjacent taps then at least partially Abgriffsspan voltages can be provided, which are determined according to the above-mentioned code, different from 1, integer multiples times the smallest tap voltage U _Xmin . The cheapest code here is the pure binary code, where each tap voltage occurs only once and between successive tap pairs in turn the tap voltages 1 · U _Xmin , 2 · U _Xmin , 4 · U _Xmin , 8 · U _Xmin , etc. fall.

However, the use of this code requires that tap pairs, which are not needed for the additive composition of a control voltage U _{S n} just required, can be easily short-circuited.

In a preferred AC voltage source, which consists of an additional transformer arrangement with a winding to which an AC voltage is applied to and which is divided into a plurality of Wicklungsab sections, between which the taps for picking up the tap voltages U _X ₁,. , , , U _Xp are brought out, the above-mentioned condition for the use of a pure binary code is not given. Therefore, a code is preferably used here, which allows each required control voltage from a group of immediately consecutive tap pairs tap, as far as they can not be tapped directly from a single tap pair. In general _terms , this means that at least the smallest handle voltage U _Xmin , in some cases, but also some of the integer multiples thereof, must be repeatedly tapped off. So z. B. for the generation of eight control voltages

1 · U _Smin , 2 · U _Smin,. , , 8 · U _Smin

on the winding of the auxiliary transformer assembly be provided four winding sections, the winding numbers are chosen so that at the taps of the series after the tap voltages

1 x U _Xmin , 2 x U _Xmin , 4 x U _Xmin , 1 x U _Xmin

fall off, where U is _Xmin = U _Smin . It can be seen that the control voltages 1 × U _Smin , 2 × U _Smin and 4 × U _Smin can be used directly at the first or second or third winding section (in the above row counted from the left), while the control voltage 3 U _Smin via a combination of the first and second winding section, the control voltage 5 · U _Smin via a combination of the third and fourth winding section, the control voltage 6 · U _Smin via a combination of the second and third winding section, the control voltage 7 · U _Smin over a com bination of the first, second and third winding section and the control voltage 8 · U _Smin on the combination of all four winding sections can be accessed abge. However, the code just given as an example is not the only one possible with this number of required control voltages and four provided coil sections. For example, all eight control voltages can also be tapped if the integer multiples of the smallest tap voltage correspond to the code 1, 3, 2, 2.

Preferably, the number of turns of the Windlungsab sections are chosen such that at the portion which is located at the one of the two ends of the winding section series, the tap voltage 1 · U _Xmin and at the Ab section, which lies at the opposite end, the tap voltage 1 · U _{Xmin are} directly accessible, as is the case with the first of the two examples above.

It is essential that the code is always chosen so that with minimal number of winding sections or from all the necessary control voltages U _{S ν} are available. In addition, if possible, the maximum AC voltage which can be tapped off via the combination of all winding sections should be equal to or at least not significantly greater than the maximum required control voltage U _Smax .

Preferably, there is the additional transformer arrangement only from one single, into the different sections divided winding, at the extreme ends of an ent speaking alternating voltage is applied. For this purpose can for example, the input or output voltage serve the actuator itself.

In order to be able to use as a voltage stabilizer and / or voltage regulator to a transformer circuit comprising an actuator, at the further winding by means of switches in the manner just described different control voltages can be applied, is further provided that the voltage applied to the load U _L measured by means of a probe arrangement, that a comparator the output signal of the sensor arrangement with a reference value U _ref equalizes ver, the set value S _{L of} the load voltage Represents animal benefits, and that a switch control is provided, the basis of the difference signal output from the comparator arrangement is, controls the switch such that the voltage induced in the first winding of the transformer voltage changes Δ _ν U counteract fluctuations may occur the load voltage U _L and compensate for these fluctuations.

The invention is described below with reference to execution Examples and with reference to the drawing be wrote; in this shows  

Fig. 1 two units to each other in series actuator constituting an actuator unit pair,

Fig. 2 shows a detail from Fig. 1, the single units of the one sensor unit reproduces,

Fig. 3 is a a single-phase voltage stabilizer connected to built transformer circuit with three stages in series,

Fig. 4 shows another embodiment of a voltage constant for a 3-phase system, and

Fig. 5 shows an embodiment in which a Stellein unit in a variety of switching states can be ge introduced and used as a voltage regulator Ver.

Fig. 1 shows an AC voltage source 1 , the Ver supply voltage U _V outputs, which is the input terminals 2 , 3 of a first actuator 54 as input voltage U _{E is} supplied. At the output terminals 5 , 6 of the actuating unit 54 appears an output voltage U _A , the A input terminals 2 ' , 3' a second actuator 54 ' as input voltage U _E ' is supplied, which has the same structure as the first actuator 54 . The output voltage U _AP output at the output terminals 5 ' , 6' of the actuator 54 ' is applied to the load 7 as the load voltage U _L.

With the aid of each of the two actuation units 54 , 54 ' , the amplitude of the respective output voltage U _A or U _{AP can be} varied with _respect to the amplitude of the associated input voltage U _E , U _E '. For this purpose, each actuator 54 , 54 ' comprises a transformer 8 , 8' , the first winding 9 , 9 ' between the input terminal 2 , 2' and the output terminal 5 , 5 'is connected, while each of the input terminal 3 , 3' with the output terminal 6 , 6 ' by means of a line 10 , 10' is connected directly electrically conductive. In this way, viewed from the voltage source 1 , the two first windings 9 , 9 ' are connected to one another and to the load 7 in series.

Each of the two transformers 8 , 8 ' has two white tere windings 35 , 36 and 35' , 36 ' , of which one as adding additional winding 35 , 35' with its one end fixed to the end of the first winding 9 , the 9th ' Is electrically connected, which is connected directly to the input terminal 2 , 2' galvanically conductive, while the other end of the adding winding 35 , 35 ' by means of a scarf age 37 , 37' to the line 10 , 10 ' or from this can be separated. The other of the two other windings is as subtracting further winding 36 , 36 ' with its one end firmly and directly galvanically connected to the end of the first winding 9 , 9' , which di rectly galvanically conductive to the output terminal 5 , 5 'of the respective Actuator 54 , 54 'is connected, while the other end of the subtracting further winding 36 , 36' by means of a switch 38 , 38 ' with the line 10 , 10' can be connected or disconnected. The scarf ter of each actuator 54 , 54 ' are driven so that only one of them is closed. In this way, each of the two actuating units 54 , 54 ' can be brought into one of the following two switching states independently of the switching state of the respective other actuating unit:

In a first switching state in which the switches 'closed and the switch 38 or 38' 37 and 37 is geöff net, is applied to the other winding 35 or 35 ', the output voltage U A and U _{E E'} applied. The space defined by the points 19, 20 and 19 ', 20' winding direction of the Wicklun gen 9, 11 or 9 ', 11' is selected such that the voltage Δ U ₁ and Δ U ₁ ', which in This first Schaltzu was in the first winding 9 , 9 'is induced, added to a input voltage U _E and U _E '.

In a second switching state, the switches 37 and 37 'are opened and the switches 38 and 38' are closed, whereby the output voltage U _A or U _{AP of} the actuating unit 54 or 54 ' is applied to the further winding 36 or 36' , At the same time, the winding sense of the further winding 36 , 36 'is reversed relative to the first switching state. Since subtracted by the voltage Δ U ₂ or Δ U ₂ ', which is induced in this switching state in the first winding 9 , 9' , of the input voltage U _E and U _E '.

Since the occurring in these two switching states in the actuator 54 and 54 ' losses are well below 1% of the load power, such a transformer circuit forms an extremely advantageous way, starting from a given input voltage U _E digitally different output voltages U _AP available ,

In a further switching state, both switches 37 , 38 and 37 ' , 38' are opened. The circuit of the other Wick lungs 35 , 36 and 35 ' , 36' then has a nearly un finally high resistance, the formation even after Heruntertrans formation on the side of the first winding 9 , 9 ' provides a high resistance value, so that at the first Winding occurs depending on the size of the load current voltage drop occurs. This throttling effect of the first winding 9 , 9 ' in this further switching state can be used to limit the power supplied to the load at least as long as an unsuccessful measure until a further short-circuit occurs on the load until further shutdown measures have been taken.

Furthermore, a switch control 23 is provided, which via the lines 26 , 27 and 26 ' , 27' the Ansteuersig signals for the switches 37 , 38 and 37 ' , 38' emits. All recently, the lines 26 , 27 and 26 ' , 27' are not directly connected to the associated switches, but each to an input of an AND gate 39 , 40 and 39 ' , 40' placed, the other input from a sensor unit 42nd or 42 'is controlled. Each of the sensor units 42 , 42 ' has two input terminals, with the help of which they interrogate about the associated switch 37 , 38 and 37' , 38 ' lapping voltage. The purpose of these sensor units 42 , 42 ' and the AND gates 39 , 40 and 39' , 40 ' is to ensure that each of the two switches 37 , 38 and 37' , 38 ' only by a corresponding signal of Switch control 23 can be closed when the respective switch has been previously opened.

If, for example, as it is posed for the actuator 54 , the switch 37 is closed, then falls over this switch 37 no voltage. Therefore, the associated sensor unit 42 generates at its output a logical 0 signal which blocks the AND gate 40 and prevents the switch controller 23 from receiving a closing signal to the switch 38 . This switch can therefore only be closed when the switch 37 has been opened, which indicates the sensor unit 42 by supplying a logic 1 to the AND gate 40 . The same applies vice versa also for the query of the closed state of the scarf age 38 by the associated sensor unit 42 and a ent speaking blocking or release of the AND gate 39 and for the corresponding switches and gates of Sen sor unit 54 ' .

Are used as switches 37 , 38 and 37 ' , 38' triacs, they can not be directly controlled by the AND gate 39 , 40 and 39 ' , 40' , but it is between tween the output of these AND gates and the gate of the triac provides one of the usual triac drive circuits, which are omitted in FIG. 1 for the sake of clarity. The sensor circuits 42 , 42 ' are wei ter explained below with reference to FIG. 2 in more detail.

If one of the two actuators 54 , 54 ' from the first switching state to the second or from the second Schaltzu state in the first pass, so far closed-ended switch 37 or 38 or 37' or 38 'must open and a short time later the previously opened Switch 38 or 37 or 38 ' or 37' are closed. The respective output voltage as soon as possible and without the occurrence of additional voltage spikes or voltage drops from the old to the new amplitude value.

To achieve this, it is expedient, the previously closed-ended switch 37 or 38 or 37 ' or 38' then open when the associated winding 35 or 36 or 35 ' or 36' flowing through current has a zero crossing. Verwen det you as a switch triacs, this results in this opening at the right time, ie at the zero crossing of the current automatically by the fact that after the self-erasure of the triac concerned at the current zero crossing prevents re-ignition in the other direction. The closing of a previously open switch is preferably carried out at such phase angles of the winding 9 and 9 ' by setting magnetic flux, in which caused by the closing of the respective switch changing the Magnetflus ses is as small as possible. The phase angle of the magnetic flux at which this criterion is met, depends on the load current, so that it can be specified for him no exact value, but only an area. For the switch 37 or 37 ' , this area is in the vicinity of the zero crossing of the magnetic flux, while it is for the switch 38 or 38' in the vicinity of the maximum of the absolute value of this magnetic flux.

To determine the most favorable closing times for the switch 37 or 38 or 37 ' or 38' , the transformer 8 , 8 'has a fourth winding, which serves as a sensor winding 43 , 43' . In this sensor winding is at clamping switches 37 and 38 or 37 ' and 38' induces a clamping voltage, which has independent of the load, a constant phase shift relative to the magnetic flux in the winding 9 and 9 ' has. This phase shift is constant equal to 90 °, so that the switch 37 , 37 ' always in the range of the absolute value maximum of this voltage and the switch 38 , 38' must be closed in the range of a zero crossing of this voltage. The information required for this purpose is the switch control 23 of the winding 43 and 43 ' via the lines 44 and 44', respectively.

An example of the sensor units 42 , 42 ' shown only schematically in FIG. 1 will be explained below with reference to FIG. 2. In this case, only the two connecting lines to the respective control unit are given in Fig. 2, the top of the associated switches, for example, the voltage drop at the switch 37 , and the line down the drive signal for the AND gate of the other switch , for example, for the AND gate 40 of the switch 38 outputs. The above the switch 37 in the open state falling AC clamping voltage is rectified by means of a rectifier 46 , the DC voltage outputs via a resistor 47 and a photodiode 48 of an optocoupler 49 are interconnected. A phototransistor 50 of the optocoupler 49 is on the one hand via a resistor 51 with a Ver supply voltage V and on the other hand directly connected to ground. The tapped off between the collector of the phototransistor 50 and the resistor 51 with respect to the ground voltage is fed via a line 52 to an inverter 53 , the output of which is connected to the AND gate 40 leads to the output line, the closing signals over the line 27 from the switch controller 23 can men, release or block.

If the switch 37 is opened, the rectifier 46 generates a DC voltage which then causes the diode 48 of the opto-coupler 49 to light up from the alternating voltage which then drops at the switch 37 . The then output from the phototransistor 50 "low" signal is inverted by the inverter 53 in a "high" - signal that releases the AND gate 40 .

If, on the other hand, the switch 37 is closed, then no AC voltage drops across it, and the rectifier 46 does not generate a DC voltage. Thus, the diode 48 of the optocoupler does not light, and the phototransistor 50 outputs a "high" signal, which is inverted by the inverter 53 in a "low" signal to disable the AND gate 40 .

As already mentioned, each of the two actuating units 54 , 54 'can be brought into three different switching states. If one leaves aside the switching state which is only possible in the case of an emergency of a load short circuit, in which the switches 37 , 38 , 37 ' , 38' are all open, then for each of the two actuating units 54 , 54 ' the operating switching states only remain the first two switching states into which they can be brought independently.

This results in a total of four different switching state combinations for the transformer circuit shown in Fig. 1.

Each of the two actuators 54 , 54 ' can be guided to their input voltage U _E or U _E ' only with modi ter amplitude, ie either with an additive or a subtractive voltage change impressed + Δ U ₁ or - Δ U ₂ or + Δ U ₁ 'or - Δ U ₂' continue. Since the turns ratios of the further windings 35 , 36 and 35 ' , 36' to the respectively associated first winding 9 , 9 ' can in principle be determined independently of one another, the 39914 00070 552 001000280000000200012000285913980300040 0002003546614 00004 39795 total can be given four different supply voltages U _V Generate load voltages U _L.

Preferably, however, these Windungsverhältnisse to form a set of actuator pairs are set so that the percentage increase of the output voltage U _{AP of} the pair with respect to the input voltage U _{EP of} the pair, resulting in closed switches 37 , 37 ' , equal to the percentage reduction of the output voltage U _AP relative to the input voltage U _EP , which results in closed switches 38 , 38 ' , and that the output voltage U _{AP is} equal to the input voltage U _EP with great accuracy when the switches 37 and 38' are closed, ie the front , ie closer to the voltage source 1 located actuating unit 54 in the first switching state and the rear actuator 54 'is in the second switching state. In this special switching state combination, therefore, the effects of the two actuators 54 and 54 ' cancel each other out approximately, so that applied to the load 7, the output from the voltage source 1 AC voltage virtually unchanged. It is of particular importance that this unaltered passing of a voltage input of the actuator units to the output is almost lossless, so that even if you turn several such actuator units in a row, an efficiency of more than 99% can be achieved.

The actuator unit pair thus has four switching state Combinations, of which three through the following equations to be discribed:

U = U ₁ _AP + _EP Δ U ₁ + Δ U ₁ '= U _EP + Δ U _P,

U _AP ₂ = U _EP + Δ U ₂ + Δ U ₂ '= U _EP - Δ U _P ,

U _AP ₃ = U _EP + Δ U ₁ + Δ U ₂ '= U _EP .

The fourth switching state combination remains un used.

Such a pair of actuator units offers the advantage that, given the size of the aufzuprägenden voltage and thus the power to be switched each of the two Stellein units only half of this switching capacity must handle and therefore can be dimensioned correspondingly smaller. Although you need a transformer more, but the two transformers are 8 , 8 'of the actuator unit pair 54 , 54' together only slightly larger and heavier than the one transformer of an actuator, which alone must provide the same switching performance. A single actuator 54 or 54 ' is in any case considerably smaller and lighter than a set for the total switching capacity of a stage actuator, ie there are smaller and lighter subunits, resulting in arrangements in which a plurality of such Stellein units or actuators Pairs in a row ge, significant structural benefits brings. Also, the transport is much easier, if you can disassemble such a system into several smaller and lighter subunits. In addition, two smaller units offer the advantage that they lead to smaller losses than a single unit with the same switching capacity.

In Fig. 3, a transformer circuit is shown, which serves as a single-phase voltage constant for the load 7 supplied voltage U _L. It is assumed that for the amplitude of the load 7 supplied AC voltage setpoint S _L is set, which is set in the following equal to 100%, and of which the actual Lich applied to the load 7 voltage by a maximum of ± δ % may deviate. Furthermore, it is assumed that the voltage supplied by the AC voltage source 1 supply voltage U _{V may} differ in its amplitude by ± Δ % of the nominal value U _Vnenn . In principle, the setpoint value S _{L of} the load voltage U _{L can be} equal to the nominal value U _{Vnenn of} the supply voltage U _V or of this nominal value. It is a particular advantage of he inventive transformer circuit is that it readily allows the load voltage U _L also on a target value S _L , regulate, for example, at or near the boundary of the proposed rule range. However, this is only expedient moderate, if deviations of the supply voltage can occur only in one direction. If the versor supply voltage z. B. generated by means of an inverter from a battery assembly, this is prior to suspension readily given, since the battery DC voltage and thus the amplitude of the he testified he AC voltage during prolonged operation with advancing discharge of the battery assembly only but can not increase.

In the following, however, the first case (U _Vnenn = S _L ) is considered and it is assumed that Δ » δ , so that a regulation of the amplitude of the supply voltage U _V to the desired value S _{L is} required.

For this purpose, a transformer circuit according to the invention is provided between the voltage source 1 and the load 7 , which consists of three together geschal ended stages 55 , 56 , 57 , each of which is formed by a pair of actuator units 54 , 54 'shown in FIG becomes. The control of the stages 55 , 56 , 57 by means of a switch control 23 which is connected to each stage 55 , 56 , 57 via a pair of wires 61 , 62 . These pairs of lines symbolize the lines 26 , 27 , 44 , 26 ' , 27' and 44 ' of FIG. 1.

About the lines 61 , the switch control 23 outputs the switching commands to the switches of the stages 55 , 56 , 57 and receives via the lines 62, the information generated by the sensor 43 information about the phase position of the magnetic flux in the first windings 9 of the Trans formators 8 and so over the favorable closing time points or periods for the switch. Furthermore, a first comparator 63 is provided, at one of its two inputs a reference voltage U _ref ₁ it holds that provides the desired value S _L for the load voltage U _L represents. The other of its two inputs, the output of a first sensor 64 is supplied, which measures the load voltage U _L. Via the line 65, the comparator 63 outputs a differential signal to the scarf ters control 23, indicating whether and how far the load voltage U _L deviates from the target value S _L. Before this deviation from the permissible range ± δ % runs out, the switch controller 23 changes the switching states of the stages 55 , 56 , 57 , which then the supply voltage U _V impose a new amplitude change and thus the load voltage U _L within the allowable control range ± δ % hold. In addition, a second comparator 66 is provided which ver equal to the nominal value U _Vnenn the Ver supply voltage U _V reference voltage U _ref ₂ with the output signal of a second sensor 67 , which measures just this supply voltage U _V. The difference signal output by the second comparator 66 is also supplied via the line 68 to the switch controller 23 , which thus can operate not only in the control mode but also in the control mode or in a combination of both. This offers the advantage that when a short circuit on the load side, ie at U _L = 0, the switch control from the fact that U _{V is} still different from zero, can detect the accident and does not try to regulate the load voltage U _L ; instead, it can bring the actuators of all stages in the above-defined third switching state, in which the first windings 9 of all transformers 8 exert a strong throttle effect and thus limit the load short-circuit current. To process the lines 62 , 68 and 65 via the lines and to convert this information into appropriate switching commands, the switch controller 23 preferably comprises a microprocessor.

As already mentioned, the stages 55 , 56 , 57 are built up such that each stage increases the input voltage supplied thereto in a first switching state combination by a predetermined percentage, in a second switching state combination is reduced by approximately the same percentage and in a third switching state combination passes approximately unchanged.

The predetermined percentages by which the individual stages can change the input voltage supplied in each case are different from stage to stage and are preferably approximately in the ratio of multiply powers of three. Thus, in the ge in Fig. 3 showed embodiment, the last stage 57 , the load 7 is closest to the input voltage supplied to her, for example, change by ± A % or pass almost unchanged. The middle stage 56 can change the input voltage supplied to it by approximately ± 3 A % or pass it on almost unchanged and the foremost stage 55 closest to the voltage source 1 can change the input voltage supplied to it by approximately ± 9 A % or pass it on almost unchanged ,

Table 3

This is shown in Table 3 again in more detail for the case that ± A % ≈ ± 1% is selected, so that for the actuator unit of the middle stage 56 a possible amplitude change of about ± 3% of this pair input voltage and for the adjusting unit pair of the foremost stage 55 results in a possible amplitude change of about ± 9%.

As can be seen from Table 3, it is expedient to Achieving as symmetrical a change as possible respective input voltage of a set of actuator pairs which can be achieved by the individual further windings percentage voltage changes at least partially to choose differently.

Thus, for the pair of the foremost stage 55 , it holds that the adding winding of the actuator 54 is capable of causing a change of + 4.5%, while the subtracting winding may cause a change of -4.9%, and the adding or subtracting winding of the actuator 54 'can impose a change of + 4.4% and -4.2%, respectively, on the input voltage of this rear stage 54' of the stage 55 .

These percentages are selected by an appropriate choice of the turns ratios so that the total changes shown in Table 3 on the right, which are + 9.1%, -8.9% and + 0.1% for the three switching states used in the first stage , These three values are 0.1% higher than the targeted + 9%, -9% and 0%. As a result, the voltage is offset waste, the units when flowing the load current due to the remaining throttle effect at the respective first turns of these two adjusting units 54 , 54 ' results.

The same applies to the step 56 , with about 0.02% to 0.03% higher values, as can be seen from Table 3 readily.

In Table 4, similar to Table 2 on the left, the twenty-seven switching state combinations that can be achieved with a three-unit-pair transformer circuit according to Figure 3 are listed, if only three switching state combinations are used for each actuator pair , Since, in addition is shown in Table 4 for each actuator 54, 54 'of the reproduced three actuating unit pairs, whether the adding or subtracting the winding is connected to the corresponding to input and output voltage. A "1" means that the respective further Wick ment is connected to the associated voltage, while a "0" indicates that the winding by opening the be taken switch 37 , 37 ' and 38 , 38' of the Lei device 10th (See Fig. 1) separated and thus not connected to the A input or output voltage. The number combination 1001 for a pair of actuators be thus suggests that in the front, that is closer to the voltage source 1 actuator, the adding winding turned on and the subtracting winding is turned off, while at the rear, closer to the load 7 arranged actuator the adding Winding turned off and the subtractive winding is turned on. Thus, a pair of actuator units marked in this way is located in the above-defined third switching state combination, in which the effects of the front and rear actuating units virtually cancel each other out, so that the input voltage at the output of the actuator unit pair appears with almost unchanged amplitude ,

Table 4

In the combination n = 0 are all three Stell units pairs in the state just described and it takes the rightmost column of Table 4, that the ratio of load voltage U _L to supply voltage U _V in this case equal to 1.0014 is practically equal to 1.

In contrast, z. B. at n = 13⁺ all three actuator unit pairs in a state in which in both actuators the adding winding is turned on (first switching state combination characterized by 1010). The right column takes one that here the load voltage U _L is 13.52% greater than the supply voltage U _V.

The switch controller 23 selects this combination when the supply voltage U _V has dropped sharply from the setpoint.

Assuming that the deviation ± δ % of the load voltage from the sol value S , which is set here equal to 100%, may amount to a maximum of ± 0.5%, the supply voltage U _{V may} drop to 87.65% of this setpoint, because the transformer circuit according to the invention can raise this from 13.52% (based on U _V = 100%) from the lowered supply voltage U _V , the resulting value for the load voltage of

U _L = U _V x 1.1352 = 87.65 x 1.1352% = 99.5% (based on the setpoint)

is at the lower limit of 99.5% (based on the Setpoint) and thus within the permissible range.  

For the switching state combination n = 13 ^- applies accordingly, that here the supply voltage U _V can be increased to 114.84% of the setpoint without the load voltage

U _L = U _V · 0.8751 = 114.84 · 0.8751 = 100, 496% (relative to the target value)

the upper limit exceeds 100.5% of the permissible range increases.

The same can be achieved for all other switching state combinations n . Preferably, such values of the supply voltage U _{V are} always transferred from one switching state combination to the next, in which the amplitude of the load voltage U _Lvor before switching and the amplitude of the load voltage U _{Lnach are} approximately symmetrical after switching to the setpoint value S _L [ see above equation (13)]. From the above values it can be seen that, in this exemplary embodiment, fluctuations in the supply voltage U _V of + Δ = 14.84% (relative to the setpoint S = 100%) to - Δ = -13.35% (also referred to S = 100 %) can be compensated such that the load voltage U _L fluctuates only within a range of S ± 0.5%.

If a larger fluctuation range ± Δ % to be detected, either the minimum amplitude change A must be increased, which is at the expense of the control accuracy δ , or it must be increased, the number of stages. It may be useful to add a step whose range of change is not equal to the next integer power of three of A , here not equal to ± 27 A , but only an integer multiple less than 27 of A , which is so great that if all four stages in the same direction, ie all act additive or all subtractive, the required fluctuation range ± Δ can just be covered.

Fig. 4 shows a modification of the invention scarf processing arrangement, as they can be used to control the output from a three-phase network voltage use.

As can be seen from Fig. 4, for each of the three phase conductors R , S and T, a Trans formator circuit according to the invention 75 , 76 , 77 is provided, which is constructed in each case in the same manner as the transformer circuit in Fig. 3. So there is each of these three transformer circuits 75 , 76 , 77 of three series-connected stages 55 , 56 , 57 , each of which here consists of a pair of actuator units 54 , 54 ' and can assume four different switching states. Thus, the AC voltage can be impressed on each of the three phase conductors R , S and T change amounts that are related to each other in the ratio 1: 3: 9, or it can be the input AC voltage passed unchanged or it can be throttled, the load current.

To the steps of the transformer circuits 75, 76, 77 to be moved into the three different switching states in the required manner, each of the Transfor is matorschaltungen 75, 76, 77, not only with their related contractual phase conductors R, S and T, but also with connected to the neutral conductor N. The voltage source used here is a three-phase network 80 .

The supplied on the individual phase conductors R , S , T from the network 80 voltage amplitudes are constantly measured by means of a sensor arrangement 81 which supplies the three measuring signals to a comparator 82 . There, the measured signals are compared with a common reference value U _ref . Alternatively, a separate reference value can also be given for each phase conductor R , S and T.

The comparator 82 generates a separate difference signal for each of the three phase conductors R , S , T , which is supplied to a switch control 83 . This controls, via the line groups 85 , 86 , 87 , the switches of the stages 55 , 56 , 57 in each of the transformer circuits 75 , 76 , 77 in the manner explained above in detail. Of course, each Stellein unit is also connected via several lines with the switch control 83 , as shown in Fig. 1 Darge is. For the sake of simplicity, however, these lines have been shown in FIG. 4 only as a single bidirectional line.

The output of each transformer circuit 75 , 76 , 77 forms a phase conductor R _K , S _K and T _K , wherein the letter "K" indicates that an AC voltage with a constant held amplitude is available on these phase conductors. These voltages can be supplied either together to a single, a three-phase current required load or different loads, each of which must be operated with a single-phase alternating current.

Alternatively, even in a multi-phase system, the sensor arrangement 81 may be designed such that it measures the AC voltages applied to the phase conductors R _K , S _K , T _K or the loads.

For larger demands on the control accuracy or even larger control ranges more than three stages can be provided even in the transformer circuits 75 , 76 , 77 . Analogous to Fig. 4, the circuit arrangement according to the invention can also be used in multi-phase systems comprising less than or more than three phases.

In Fig. 5, another embodiment of he inventive transformer circuit is shown, which comprises only a single actuator 94 . As in the embodiment shown in FIG. 1, the input terminals 2 , 3 of the Stellein unit 94 is supplied as input voltage U _E, a supply voltage U _V , which originates from a voltage source 1 here . At the output terminals 5 , 6 appears an output voltage U _A , which is performed to a load 7 as a load voltage U _L to. Furthermore, the actuator 94 comprises a transformer 8 , whose first winding 9 is connected between the input terminal 2 and the output terminal 5 , while the other input terminal 3 is connected to the second output terminal 6 by means of the line 10 directly galvanically conductive. Also, the transformer Trans 8 has another winding 11 which is magnetically coupled via the iron core 12 of the transformer 8 to the first winding 9 .

However, in contrast to the embodiment in Fig. 1, the actuator 94 of the present embodiment can be brought not only in three, but in thirty four different switching states, so that it is possible, a total of thirty-two different amplitude differences between the input voltage U _E and the output voltage U _A of an actuating unit 94 to produce the input voltage U _E unchanged at the output terminals 5 , 6 available to throttle or in the case of a short circuit to the load load.

This large variation possibility makes it possible to set the transformer circuit shown in Fig. 5 similar to the transformer circuits in Figs. 3 and 4 as a voltage regulator and / or Spannungskonstanter einzu.

In Fig. 5 the use case is shown as a voltage regulator, in which in turn a Meßfühleranordnung 64 via lines 95 , 96, the output voltage U _{A of} the actuator 94 , which here is equal to the load voltage U _L, is supplied. The sensor 64 outputs a detection signal to a comparator 63 further compares this measurement signal with a reference voltage U _ref corresponding to the reference value S _L of the load voltage U _L. Via the line 65 , the comparator 63 is a difference between the measuring signal and the reference voltage U _ref representing differential signal to a switch control 23 on lines 97 one of fourteen switches best rising switch group 98 controls to the actuator 94 in the various switching states bring, as will be explained in more detail below.

In addition to the two switching states in which the other winding 11 is either short-circuited or fully open to bring the actuator 94 in thirty-two other switching states must be applied to the other winding 11 thirty-two control voltages U _S ₁ to U _S ₃₂, according to of the invention using a single AC voltage source 100 are generated.

The AC voltage source 100 is formed by an additional transformer arrangement 101 , which consists in the present case of six electrically interconnected in series winding sections 104 to 109 , which are magnetically coupled together via a common transformer core 111 .

The one end of the series consisting of the winding sections 104 to 109 series circuit is electrically directly connected to the one pole of the AC voltage source 1 , to which also the input terminal 3 of the actuator 94 is connected, via the line 10 directly electrically conductively connected to the output terminal 6 of Actuator 94 is connected. The other end of the series circuit consisting of the winding sections 104 to 109 is connected via a line 114 to the second output terminal 5 of the actuator 94 . Thus, the output voltage U _{A of} the actuating unit 94 is applied to the series connection of the winding sections 104 to 109 .

The series connection of the winding sections 104 to 109 has seven taps 121 to 127 , of which the taps 121 and 127 are connected to the two outer ends of the series circuit, while the taps 122 to 126 are led out between each two adjacent winding sections.

Each of the taps 121 to 127 is connected to a pair of on / off switches of the switch group 98 . The one switch of each pair of switches connects in the closed state the associated tap with a line 129 which is connected to the lower end of the further winding 11 in FIG . The other switch of each pair connects in the closed state, the associated tap with a line 130 which is in communication with the other end of the other winding 11 . All switches of the switch group 98 are, as already mentioned, driven by the switch control 23 via the lines 97 such that the currently required control voltage U _{S 1} to U _{S 32} is applied to the further winding 11 , or that the two switches of an arbitrary pair are closed simultaneously to short circuit the other winding 11 , or that all switches 98 are opened to throttle the load current.

For a symmetrical control of the load voltage U _L to the setpoint S _L , the actuator can be placed in thirty-two different switching states, of which sixteen to the additive impression of each induced voltages Δ U ₁ to Δ U ₃₁ and sixteen to the negative impact of each induced voltage Δ U ₂ to Δ U ₃₂ are provided. The amplitude of each positively impressed voltage is equal to the amplitude of a correspondingly negative impressed voltage.

Since the sign of the imprint results from the winding sense, with which the further winding 11 is connected to a control voltage, so only sixteen control voltages U _{S 1} to U _{S 16} with different amplitudes are required because the further winding 11 with the aid of the switch 98th with two different directions of the winding sense to the various taps 121 to 127 can be placed.

In order to be able to tap the sixteen different control voltage amplitudes, the numbers of turns of the winding sections 104 to 109 are coordinated according to a code which is optimized so that on the one hand the smallest possible number of winding sections 104 to 109 and thus taps 121 to 127 and switches 98th is needed, and on the other hand, the maximum required control voltage U _Smax between the farthest taps 121 and 127 can be tapped.

According to this optimized code, the winding section 109 has such a number of turns that, when the output voltage U _{A of} the control unit 94 is applied to the series connection of all winding sections 104 to 109 , a tap voltage 1 * U _{Xmin can be} tapped from this winding section 109 which requires the smallest Control voltage U _Smin corresponds.

By simultaneously closing the in Fig. 5 upper switch of the switch pair 130 and the lower switch of the pair of switches 131 so the smallest required control voltage U _Smin can be applied to the further winding 11 so that the thus induced in the first winding 9 of the transformer 8 voltage Δ U _{min is} subtractively impressed on the input voltage U _E. If, instead, the lower switch of the pair 130 and the upper switch of the pair 131 are simultaneously closed in FIG. 5, then the same smallest control voltage U _Smin is applied to the further winding 11 , but the winding sense of the further winding 11 is inverted with respect to the preceding case , So that now the induced voltage Δ U _{min is} impressed additive to the input voltage U _E. The same applies to the tapped between any other taps 121 to 127 control voltages.

According to the optimized code, the number of turns of the remaining winding sections 104 ibs 108 are selected such that the following tap voltages are available between adjacent taps 121 to 126 :

Abgriffspaar U _X 121, 122 2 × U _Xmin 122, 123 1 × U _Xmin 123, 124 4 × U _Xmin 124, 125 6 · U _Xmin 125, 126 2 × U _Xmin

Together with the voltage 1 · U _Xmin at the tap pair 126, 127 , this results in the possibility of tapping all control voltage amplitudes from 1 · U _Smin to 16 · U _Smin either directly at immediately adjacent taps or between farther apart taps, as shown in Table 6 below is shown:

control voltage taps 1 · U _Smin 126, 127 2 · U _Smin 125, 126 3 · U _Smin 125, 127 4 · U _Smin 123, 124 5 · U _Smin 122, 124 6 · U _Smin 124, 125 7 · U _Smin 121, 124 8 · U _Smin 124, 126 9 · U _Smin 124, 127 10 · U _Smin 123, 125 11 · U _Smin 122, 125 12 · U _Smin 123, 126 13 · U _Smin 123, 127 14 · U _Smin 122, 127 15 · U _Smin 121, 126 16 · U _Smin 121, 127

It can be seen that here, too, the optimized code is characterized in that at the one end of the series connection winding section 109 is 1 times the minimum tap voltage U _Xmin and at the other end lying winding section 104 can be tapped twice of U _Xmin .

In order to obtain appropriate conditions as in the embodiment shown in FIG. 1, it may be provided in the embodiment shown in FIG. 5 that the line 114 is not firmly connected to the line 95 at the point 140 . Instead, here two push-pull actuated switches can be arranged, with the help of which the series circuit of the windings 104 to 109 remote end of the line 114 via corresponding lines either with the output terminal 5 to the load 7 line leading or with the voltage source 1 to the input terminal 2 leading line can be connected. These switches are then also driven by the switch controller 23 to apply to the series circuit of the windings 104 to 109, either the input voltage U _E or the output voltage U _{A of} the actuator 94 . The former preferably takes place when, by a corresponding to the further winding 11 applied control voltage U _{S 1} ,. , ., U _{S 31} in the first winding 9, a voltage Δ U ₁,. , ., Δ U ₃₁ to be induced, which impresses itself on the input voltage U _E additive. On the other hand, the line 114 is preferably connected to the output voltage U _A when, in the first winding 9, a voltage Δ U ₂,. , ., Δ U ₃₂ is to be induced, which subtractively impresses on the input voltage U _E.

Claims (28)

A transformer circuit comprising at least one actuator unit for generating an adjustable load voltage applied to a load from a supply voltage supplied by a voltage source, comprising:

• A transformer having a first winding in series with the load and at least one further winding whose turns ratio to the first winding is greater than one, and
• - Switch, by means of which by applying control AC voltages to the at least one further winding, the actuating unit can be brought into at least two different switching states, wherein in a first switching state in the first winding, a first voltage is induced, which impressively impresses on the input AC voltage , and in a second switching state, in the first winding, a second voltage is induced, which subtractively impresses on the input AC voltage,

characterized in that the transformer circuit comprises at least one stage ( 55, 56, 57 ) consisting of at least two actuators ( 54, 54 ' ) connected in series with each other so that the output AC voltage (U _A ) of the front actuator ( 54 ) is the AC input voltage (U _E ') of the rear actuator ( 54' ), and in that the two actuators ( 54, 54 ' ) form a pair of actuator units in that the winding ratios of the first windings ( 9, 9' ) to the further windings ( 35, 36, 35 ', 36' ) are matched to one another in such a way that the output voltage (U _AP ) of the actuator unit pair ( 54, 54 ' ) is then equal to the input voltage (U _EP ) of the actuator unit pair ( 54, 54 ' ) is, if the one ( 54 ) of the actuators to their input voltage (U _EP ) an induced voltage ( Δ U ₁) additive and the other actuator ( 54' ) to its input voltage (U _E ') an induced voltage ( Δ U ₂ ') subtractively imprinted. 2. Transformer circuit according to claim 1, characterized in that the at least two first windings ( 9, 9 ' ) of the transformers ( 8, 8' ) of the at least two actuating units ( 54, 54 ' ) are directly in series with each other. 3. Transformer circuit according to claim 1 or 2, characterized in that it comprises a plurality of stages ( 55, 56, 57 ), and in that by at least one stage ( 55, 56, 57 ) an amplitude difference between its input voltage and its output voltage can be generated is different from the corresponding amplitude differences of all other stages. 4. Transformer circuit according to claim 3, characterized in that the absolute values of the amplitude differences which can be generated by the different stages ( 55, 56, 57 ) relative to each other are in the ratio of integer triplicates 1: 3: 9 and so on. 5. Transformer circuit according to claim 4, characterized that at least one more Stage is provided, through which an amplitude difference which is one of an integer power of three different integer multiple of the smallest, by an amplitude difference producible by the remaining stages is. 6. Transformer circuit according to one of the preceding claims, characterized in that the transformer ( 8 ) has at least two further windings ( 35, 36 ) to which by means of the switches ( 37, 38 ) alternately one control alternating voltage can be applied to bring the first winding ( 9 ) in the first and second switching state. 7. Transformer circuit according to claim 6, characterized in that by applying a control voltage to the one further winding ( 35 ) in the first winding ( 9 ) induced first voltage ( Δ U ₁) has an amplitude whose absolute value is approximately equal to the absolute value the amplitude of the voltage induced by applying a control voltage to the other further winding ( 36 ) in the first winding ( 9 ) second voltage ( Δ U ₂). 8. Transformer circuit according to one of the preceding claims, characterized in that for the additive impressing an induced voltage ( Δ U ₁), the input AC voltage ( U _E ) of the respective actuating unit ( 54, 54 ' ) and for subtractive imposition of an induced voltage ( Δ U ₂ ) the output AC voltage (U _A ) of the respective actuator ( 54, 54 ' ) is used as the respective control AC voltage. 9. Transformer circuit according to claim 8, characterized in that the transformer ( 8 ) of each adjusting unit ( 54, 54 ' ) comprises two further windings ( 35, 35', 36, 36 ' ), one of which only as an adding winding ( 35 , 35 ' ) is used, which is directly galvanically connected at one end to one ( 2 ) of the two input terminals ( 2, 3 ) of the actuator ( 54, 54' ), and the other end by means of a switch ( 37, 37 ' ) with the other input terminal ( 3 ) directly galvanically conductively connected or is separable from this, and of which the other only as a subtractive winding ( 36, 36' ) is used, with one end constantly with a ( 5 ) the two output terminals ( 5, 6 ) of the adjusting unit ( 54, 54 ' ) is directly electrically conductively connected, while the other end by means of a switch ( 38, 38' ) with the other output terminal ( 6 ) directly galvanically connected or from the sem separable, and that the two switches ( 37, 37 ', 38, 38' ) are exclusively actuated. 10. Transformer circuit according to claim 9, characterized in that the two switches ( 37, 37 ', 38, 38' ) between the conductor ( 10 ) which connects the one input terminal ( 3 ) to the one output terminal ( 6 ) directly, and the respective end of the associated further winding ( 35, 35 ', 36, 36' ) are arranged, that at each of the two switches ( 37, 37 ', 38, 38' ) a sensor unit ( 42, 42 ' ) is arranged, the emits a signal which indicates the switching state of the associated switch ( 37, 37 ', 38, 38' ), and in that each of the two switches ( 37, 37 ', 38, 38' ) has a blocking circuit ( 39, 39 ', 40, 40 ' ) which, depending on the signal which is output by the sensor unit of the respective other switch ( 39, 39', 40, 40 ' ), closes the switch ( 39, 39', 40, 40 ' ), As long as the other switch ( 39, 39', 40, 40 ' ) is closed. 11. Transformer circuit according to one of claims 1 to 5, characterized in that by the switch ( 98 ) to the further winding optionally one of a plurality of control voltages (U _{S 1} ,..., U _{S 32} ) can be applied, which in two Groups (U _{S 1} , U _{S 3} , _... , U _{S 31} and U _{S 2} , U _{S 4} , ..., U _{S 32} ) are divided, that the control voltages belonging to the same group, all different from each other Amplitudes have, while each control voltage (U _{S 1} , U _{S 3} , ..., U _{S 31} ) from the one group of a control voltage (U _{S 2} , U _{S 4} , .., .., U _{S 32} ) from the other group with respect to the amplitude is at least approximately equal that the control voltages (U _{S 1} , U _{S 3} ,..., U _{S 31} ) of one group to the at least one further winding ( 11 ) can be applied, that the thereby induced voltages ( Δ U ₁, Δ U ₃, ..., Δ U ₃₁) additively impress on the input voltage (U _E ) of the actuator ( 4, 94 ) and that the control tensions (U _{S 2} ,. , ., U _{S 32} ) of the other group in such a way that at least one further winding ( 11 ) can be applied, that thereby induced voltages ( Δ U ₂, Δ U ₄,..., Δ U ₃₂) subtractive to the input voltage ( U _E ). 12. Transformer circuit according to claim 11, characterized in that an AC voltage source ( 100 ) is provided, which has a plurality of taps ( 121 ,..., 127 ), at which at the same time several Abgriffswechselspannungen (U _{X 1} ,..., U _X ) whose amplitudes are selected such that each of the control voltages (U _{S 1} , ..., U _{S 32} ) is either equal to or equal to the sum of a plurality of these tap AC voltages (U _{X 1} , ..., U _{X 6} ), and that at least one of the two ends of the further winding ( 11 ) by means of switches ( 98 ) optionally with different of these taps ( 121 ,..., 127 ) is connectable. 13. Transformer circuit according to claim 12, characterized in that the for inducing the smallest desired non-zero voltage ( Δ U _min ) in the first winding ( 9 ) of the transformer ( 8 ) required control voltage (U _Smin ) as the smallest Abgriffswechselspannung (U _Xmin ) (at least one pair of mutually directly adjacent taps 126, 127) of the AC voltage source (100) can be tapped, and that the mutually directly adjacent between the other pairs of taps (121..., 126) can be tapped Abgriffswechselspannungen (U _{X 1,} , U _{X 5} ) are either equal to this smallest tap AC voltage (U _Xmin ) or equal to an integer multiple of this smallest tap AC voltage (U _Xmin ). 14. Transformer circuit according to claim 13, characterized in that the number of taps ( 121 ,,..., 127 ), the number of Abgriffspaare ( 126, 127, 122, 123 ), between which the smallest Abgriffs AC voltage (U _Xmin ) can be tapped and the magnitudes of the integer multiples of the smallest tap AC voltage (U _Xmin ) that can be _tapped between the remaining pairs of mutually immediately adjacent taps ( 121, 122, 123, 124, 124, 125, 125, 126 ) are selected such that with a minimum number of taps ( 121, ., _... , 127 ) a predefinable maximum control voltage range (U _Smax ) in unit steps of the smallest tap AC voltage (U _Xmin ) can be covered. 15. Transformer circuit according to claim 14, characterized in that the number of taps ( 121 , ..., 127 ), the number of Abgriffspaare ( 126, 127, 122, 123 ), between which the smallest tap AC voltage (U _Xmin ) can be tapped , and the magnitudes of the integer multiples of the smallest Abgriffs AC voltage (U _Xmin ), which can be _tapped between the other pairs of mutually immediately adjacent taps, are selected such that, moreover, the maximum voltage that can be tapped at the AC voltage source ( 100 ), the same is to induce the desired maximum voltage (Δ U _max) in the first winding (9) of the transformer (8) required maximum control voltage (U _Smax). 16. Transformer circuit according to one of claims 12 to 15, characterized in that the AC voltage source ( 100 ) is a winding of an additional transformer arrangement ( 101 ), to which an AC voltage is applied and in a plurality of winding sections ( 104,, . 109 ) between which the taps ( 121, ..., 127 ) are led out to pick up the tap AC voltages (U _{X 1} , ..., U _{X 6} ). 17. Transformer circuit according to claim 16, characterized in that the AC voltage which can be applied to the winding of the additional transformer arrangement ( 101 ), the input voltage (U _E ) or the output voltage (U _A ) of the actuating unit ( 94 ). 18. Transformer circuit according to one of claims 1 to 10, characterized in that the turns ratio of the further winding ( 11; 35, 36, 35 ', 36' ) of the transformer ( 8 ) to the first winding ( 9 ) in a range of 3: 1 to 200: 1. 19. Transformer circuit according to one of claims 1 to 18, characterized in that a sensor device for detecting the phase characteristic of the magnetic flux in the first winding ( 9 ) is present, that the switches ( 37, 38, 37 ', 38' ), respectively for applying a control voltage to the further winding ( 35, 36, 35 ', 36' ) serve, depending on the measuring signal of the sensor device only at such phase angles of the magnetic flux in the first winding ( 9 ) are closable, in which this closing to a possible small change of this magnetic flux leads, and that these switches ( 37, 38, 37 ', 38' ) are opened only at the zero crossing of the current flowing through the further winding ( 35, 36, 35 ', 36' ). 20. Transformer circuit according to claim 19, characterized in that the sensor device is a sensor winding ( 43 ) of the transformer ( 8 ). 21. Transformer circuit according to claim 20, characterized in that the input voltage (U _E ) or one of the input voltage (U _E ) derived control voltage to the further winding ( 35, 35 ' ) is applied only when the magnitude of the amplitude the voltage emitted by the sensor winding ( 43 ) is in the range of its maximum, and that the output voltage (U _A ) or a control voltage derived from the output voltage (U _A ) is applied to the further winding ( 36, 36 ' ) only when the voltage delivered by the sensor winding ( 43 ) is in the range of a zero crossing. 22. Transformer circuit according to claim 19, characterized in that the transformer ( 8 ) by means of a switch ( 29 ) kurzschließbare short-circuit winding ( 28 ), and that the switch ( 29 ) for the short-circuit winding ( 28 ) is closed during the periods, in which when switching from one control voltage to another control voltage temporarily no control voltage to another winding ( 11 ) is applied. 23. Transformer circuit according to claim 22, characterized in that the switch ( 29 ) for the short-circuit winding ( 28 ) only at such phase angles of the magnetic flux through the first winding ( 9 ) is closed, in which this closing leads to the smallest possible change in this magnetic flux , and that this switch ( 29 ) is opened only at the zero crossing of the current flowing through the short-circuit winding ( 28 ). 24. Circuit arrangement with a transformer circuit according to one of the preceding claims, characterized in that an alternating voltage sensor arrangement is provided which comprises a measuring sensor ( 67, 81 ) which measures the supply voltage (U _V ) delivered by the voltage source ( 1; that a comparator (63, 66; 82) the output signals of the measuring sensor arrangement with reference values (U _{ref 1,} U _ref2, U _ref), and that by a switch controller (23; 83), the switches of the stages (55, 56, 57 ) are selectively operable so that the load ( 7 ), the load voltage (U _L ) is supplied with a constant amplitude as possible. 25. Circuit arrangement with a transformer circuit according to one of the preceding claims, characterized in that an alternating voltage sensor arrangement is provided, which comprises a measuring sensor ( 64 ) which measures the load voltage (U _L ) that a comparator arrangement ( 63, 66, 82 ) the output signals of the sensor arrangement are compared with reference values (U _{ref 1} , U _{ref 2} , U _ref ), and in that the switches of the stages ( 55, 56, 57 ) can be selectively actuated by a switch control ( 23; 7 ) the load voltage (U _L ) is supplied with a constant amplitude as possible. 26. Circuit arrangement according to claim 24 or 25, characterized in that for each of the phase conductors (R, S, T) of a polyphase system, a transformer circuit ( 75, 76, 77 ) having one or more stages ( 55, 56, 57 ), one Voltage on each of the phase conductors (R, S, T or R _K , S _K , T _K ) measuring sensor arrangement ( 81 ), a comparison of the output signals of the sensor arrangement ( 81 ) with at least one reference value (U _ref ) comparator arrangement ( 82 ) and a Switch controller ( 83 ) are present, which controls the switches of the stages ( 55, 56, 57 ) of all the transformer circuits ( 75, 76, 77 ) due to the output from the comparator arrangement ( 82 ) differential signals. 27. A method for controlling the amplitude of an AC voltage using a circuit arrangement according to one of claims 24 to 26, characterized in that the absolute value of the smallest possible amplitude change (A) between 1.0 times and 2.0 times the absolute value of the allowable deviation ( δ ) of the load voltage (U _L ) the setpoint (S _L ), and that the switching thresholds, in which with increasing deviation of the output from the voltage source supply voltage (U _V ) of the nominal AC voltage, the impressed amplitude difference of n times the smallest possible amplitude change (A ) is switched to the ( n + 1) -fold and with decreasing deviation from the (n + 1) -fold to the n -fold, are chosen such that the amplitude values of the load voltage (U _L ) during continuous passage of the supply voltage (U _V ) are symmetrical to the setpoint (S _L ) by the respective switching shaft before and after switching.