EP0095398A1 - Electric transformer with modular, selectively fed primary circuits - Google Patents

Abstract

An electric transformer for supplying an adjustable electric magnitude, especially for regulating purposes, includes several modules having therebetween a binary progression relationship with respect to their power handling capabilities. Each module has a switching network for selectively rendering it operative or inoperative and, each module has at least one primary circuit input coil, the primary coils of each of the modules cooperating with one single secondary output circuit which is common to all of the modules. The switching network of each module being so connected as to allow the neutralization of the effect of the electronic induction of its respective primary coil or coils on the common secondary circuit, while maintaining the magnetic activity of the primary circuits.

Description

The present invention relates to a variable voltage transformer.

We know that this kind of transformer tends to solve the problem of varying an output voltage from a constant nominal input voltage.

• - en galvanoplastie ils permettent d'ajuster le courant en fonction du produit traité et de la surface intéressée;
• - en transmission mécanique ils entrent dans la constitution de variateurs de vitesse;
• - en métallurgie ils assurent une alimentation des fours à induction réglables.

Such transformers have multiple applications:

• - in electroplating they make it possible to adjust the current according to the product treated and the surface concerned;
• - in mechanical transmission, they form part of variable speed drives;
• - in metallurgy they supply adjustable induction ovens.

Up to now, known transformers have had numerous drawbacks.

Thus, for example, in plug-in transformers, the secondary has several output terminals and a switch is applied selectively to one or other of these terminals to give a variable operating voltage depending on the height of the secondary to which the socket is located.

With such a device, very serious jumps and breaks in load are encountered, which require extreme limitation of the powers to be regulated and, despite this, the installation undergoes rapid wear.

There are also known slider "auto-transformers" which provide a single outlet on the secondary, but the latter is mobile and consists of a carbon roller.

It is easy to understand that when the roller passes from one turn to another it puts them in short circuit and this causes a heating of the coal which wears out quickly and which obliges to limit the power of variation.

However, there is an advantage here which comes from regulation which is almost continuous, since the pitch is of a single turn, so that if we imagine that the secon daire is formed by a coil of 220 turns, the pitch is equal to 1. 220

Magnetic amplifiers or "transducers" include a magnetic circuit and a choke coil, which makes it possible to obtain an adjustment without moving mechanical part, because one acts by saturating and desaturating the magnetic circuit by causing a phase shift.

This results in a non-sinusoidal and, by way of. Consequently, an offset between the current and the voltage which leads to a very bad cosine ϕ.

Finally, developments in electronics have made it possible to use thyristors which give a non-sinusoidal output signal and therefore analogous to that of a transducer, but without phase shift.

On the other hand, each interruption causes unacceptable current surges in practice.

• - commutation avec rupture de charge,
• - puissance d'utilisation limitée,
• - régime sinusoïdale déformé,
• - cosinus ϕ variable,
• - puissance massique identique à celle d'un transformateur normal,
• - incidence économique défavorable par le coût élevé.

In summary, the known devices have the following drawbacks:

• - switching with load break,
• - limited power of use,
• - distorted sinusoidal regime,
• - variable cosine ϕ,
• - mass power identical to that of a normal transformer,
• - adverse economic impact due to the high cost.

The present invention overcomes all these drawbacks as will be seen below, since a transformer according to the invention knows no power limit, operates with a pure sinusoidal regime, has a constant cosine ϕ, does not cause breakage load and allows an adjustment of a finesse as large as is desired because the pitch of this adjustment can be practically insensitive.

• Les figures 1 et 2 sont des vues schématiques, respectivement en plan et de face_id'un transformateur élémentaire conforme à l'invention.
• Les figures 3 à 6 sont desschémas montrant différentes solutions pour l'alimentation sélective individuelle des différents modules primaires que comporte un transformateur conforme à l'invention.
• La figure 7 est un schéma montrant la conception possible d'un tranformateur conforme à l'invention.
• La figure 8 est une vue schématique d'un mode de réalisation particulier de l'invention.,
• La figure 9 est un schéma montrant l'application de l'invention à la régulation d'un transformateur de puissance.
• La figure 10 est un schéma partiel d'une variante de réalisation.
• La figure 11 montre schématiquement une possibilité de bobinage "en huit" pour le secondaire commun à deux circuits primaires.

The invention will be better understood from the detailed description below made with reference to the accompanying drawing. Of course, the description and the drawing are given only by way of an indicative and nonlimiting example.

• Figures 1 and 2 are schematic views, respectively in plan and front _i of an elementary transformer according to the invention.
• FIGS. 3 to 6 are diagrams showing different solutions for the selective individual supply of the different primary modules that a transformer according to the invention comprises.
• Figure 7 is a diagram showing the possible design of a transformer according to the invention.
• FIG. 8 is a schematic view of a particular embodiment of the invention.,
• FIG. 9 is a diagram showing the application of the invention to the regulation of a power transformer.
• Figure 10 is a partial diagram of an alternative embodiment.
• FIG. 11 schematically shows a possibility of "eight" winding for the secondary common to two primary circuits.

The invention relates to an electrical transformer intended to deliver an adjustable electrical quantity, in particular for regulation purposes, characterized in that it comprises on the one hand at least two modules which each comprise at least one primary circuit winding and which are independent and, on the other hand, a single secondary circuit winding common to all the modules, each of these being associated with means making it possible to neutralize its individual electrical induction in the winding of the common secondary circuit, while retaining the activity of the corresponding magnetic circuit.

• - les moyens sont constitués par un connecteur individuel à chaque module et ayant deux positions, dans l'une desquelles le bobinage de circuit primaire est alimenté normalement par une tension d'origine nominalement constante et dans l'autre desquelles ledit circuit magnétique reste activé à partir de la même tension d'origine mais en induisant une tension nulle par soustraction.
• - Les deux positions du connecteur correspondent respectivement à l'alimentation normale du bobinage du circuit primaire et à sa mise en court-circuit.
• - Entre la tension d'alimentation et chacune des deux bornes du bobinage de circuit primaire de chaque module , sont intercalés deux interrupteurs électroniques tels que des thyristors ou des transistors montés tête-bêche et commandés sélectivement pour assurer l'inversion et l'alimentation dudit bobinage.
• - Chaque module comprend deux bobinages de circuit primaire alimentés sélectivement, soit pour assurer l'induction normale dans le bobinage de circuit secondaire, soit pour la neutraliser.
• - les deux bobinages sont de sens inverses, un connecteur étant prévu pour établir le contact entre la tension d'origine et l'un ou l'autre de ces deux bobinages.
• - Les deux bobinages sont de même sens et un inverseur est intercalé entre les bornes d'un seul de ces bobinages et la tension d'origine qui alimente simultanément l'autre bobinage.
• - Le bobinage de circuit primaire du premier module est alimenté par les deux lignes principales d'une source de tension et le bobinage correspondant des modules suivants est alimenté à l'une de ses extrémités par l'une des deux lignes principales et à son autre extrémité par une dérivation issue d'un point intermédiaire, notamment médian, du bobinage de circuit primaire du module précédent.
• - Les modules ont une tension nominale procurant avec un courant donné une puissance qui est différente pour chaque module, le total de ces puissances individuelles étant sensiblement égal à la puissance maximum admissible pour le circuit secondaire unique.
• - Les puissances des modules sont des fractions dégressives régulières de la puissance totale et dont les dénominateurs sont des puissances entières de deux.

According to other characteristics of the invention:

• - The means are constituted by an individual connector to each module and having two positions, in one of which the primary circuit winding is normally supplied by a nominally constant original voltage and in the other of which said magnetic circuit remains activated at starting from the same original voltage but inducing a zero voltage by subtraction.
• - The two positions of the connector correspond respectively ment to the normal supply of the winding of the primary circuit and to its short-circuiting.
• - Between the supply voltage and each of the two terminals of the primary circuit winding of each module, two electronic switches are interposed such as thyristors or transistors mounted head to tail and selectively controlled to ensure the inversion and supply of said winding.
• - Each module includes two primary circuit windings selectively supplied, either to ensure normal induction in the secondary circuit winding, or to neutralize it.
• - The two windings are in opposite directions, a connector being provided to establish contact between the original voltage and one or the other of these two windings.
• - The two windings are in the same direction and an inverter is interposed between the terminals of only one of these windings and the original voltage which simultaneously supplies the other winding.
• - The primary circuit winding of the first module is supplied by the two main lines of a voltage source and the corresponding winding of the following modules is supplied at one of its ends by one of the two main lines and at its other end by a derivation from an intermediate point, in particular median, of the primary circuit winding of the previous module.
• - The modules have a nominal voltage providing with a given current a power which is different for each module, the total of these individual powers being substantially equal to the maximum admissible power for the single secondary circuit.
• - The powers of the modules are regular decreasing fractions of the total power and whose denominators are whole powers of two.

Referring to Figures 1 and 2, we see that a transformer according to the invention can include, as here, two modules which each include a single primary winding respectively 1 and 2 each associated with a magnetic circuit respectively 3 and 4, these two primary circuits being associated with a single secondary circuit winding 5 common to the two modules 1 and 2.

Each primary winding 1 and 2 is independently connected to a nominally constant voltage source 6, for example 220 Volts.

For each winding, there is a switch respectively 7 and 8 which can occupy two positions in one of which it establishes the normal circuit (connector 8 in Figures 1 and 2) while in the other (connector 7 in Figure 1), it puts the corresponding winding in short circuit.

In this way, depending on whether the switch of each primary circuit winding is in one or other of its two positions, the single secondary circuit 5 has a voltage which corresponds either to that which results from the winding 1 only, or to that which results from the winding 2 only, that is to say that which results from the action of the two windings 1 and 2 at the same time.

A complete installation comprising a transformer according to the invention is equipped with a control device, possibly programmed, and acting on all the connectors to act selectively on the individual supply of each primary module.

As a result, by properly calibrating the primary modules, a very high degree of precision and fine tuning can be achieved.

Naturally, a simple version consists in providing a plurality of modules all equal to each other.

However, according to a more elaborate version, it is interesting to provide that the modules have a nominal voltage which is established to provide, with a given current, a power which is different for each module.

The total of these individual powers is substantially equal to the maximum admissible power for the single secondary circuit.

According to a variant of the invention which proves to be particularly advantageous, the modules are regular decreasing fractions of the total power and are established according to a binary code.

, les autres modules ayant une puis- sance égale respectivement à

,

,

,

,

, etc...In other words, the denominator of each fraction is an integer power of 2 so that the most powerful module is equal to half of the total power P, i.e.

, the other modules having a power equal respectively to

,

,

,

,

, etc ...

It can thus be seen that the adjustment step, or minimum jump, is equal to the smallest fraction of P provided in the transformer.

pour le dernier module ce qui est une excellente preformance (

)It is therefore possible in practice, without any difficulty, to make a transformer composed of a plurality of modules of decreasing dimensions which, eight in number, provide a fine adjustment equal to

for the last module which is excellent preformance (

)

, on n'active que le module N°1. Si l'on désire l'augmenter de

, on active en plus le module N°8. Pour l'augmenter encore de

on active le module N°7 en neutralisant, simultanément le module N°8 etc...When the requested power is equal to

, we only activate module N ° 1. If you want to increase it by

, we also activate module No. 8. To further increase it by

module N ° 7 is activated by simultaneously neutralizing module N ° 8 etc ...

, N-1 étant la fraction de la puissance du dernier module d'un ensemble donné.Each module being selectively controlled, all combinations are possible with a fine adjustment equal to

, N-1 being the fraction of the power of the last module of a given set.

à un réglage au

ne nécessite que l'adjonc- tion d'un transformateur supplémentaire de très petites dimensions.It should be emphasized, because this is an interesting characteristic of the invention, that each primary module is not very bulky and that the passage from an adjustment to the

to a setting at

requires only the addition of an additional transformer of very small dimensions.

Referring now to Figure 3, there is an electrical diagram of a transformer according to the invention comprising six identical modules 10 to 15 and, of course, always a single circuit winding secondary 16.

Each module comprises a coil 17 to 22 associated with an individual magnetic circuit 23 to 28.

The AC voltage source 30 is connected to two main lines 31 and 32 to which the individual power supplies of each primary module are connected respectively 33 to 38 and 39 to 44.

The type of connection chosen is that which has already been described with reference to FIGS. 1 and 2, that is to say that each module 10 to 15 is associated with a connector 45 to 50 respectively movable between two positions corresponding to the power supply normal or when each winding 17 to 22 is short-circuited.

To simplify the drawing, all the modules 10 to 15 have been shown as if they all had the same dimensions.

However, in reality, if we adopt the preferred embodiment according to which the modules provide different powers, it is clear that they have dimensions the smaller the power developed is itself low.

, pour le module 11 une puissance égale à p , etc...If we retain the binary variation of this power compared to the total power P admissible by the single secondary circuit winding 16, we have for the module 10 a power equal to

, for module 11 a power equal to p, etc ...

Assuming that the installation is supplied with 220 Volts with an effective current of 48 Amperes, we obtain the results grouped in the table below:

It emerges from the description above, that the voltage of the secondary is a function of the number of modules under voltage and that it can, therefore, vary from 0 to 100 per 100 by modifying the ratio of the number of turns of the primary windings the number of turns of the secondary winding, taking the precaution of shunting the windings of the non-activated modules to give them zero impedance, which is indeed the case since the secondary then becomes conductive.

The single transformer according to the invention functions, in a way, like a series of transformers, the secondaries of which are all in series.

This solution results in a very significant mass saving since the power of such a transformer-variator is the same as that which a conventional transformer would have without adjustment.

Referring now to FIG. 4, we will describe a transformer of the same type as that which has been described previously, that is to say of which each module comprises only one primary winding, but with the use of head-to-tail thyristors to act selectively on the induction produced by the primary winding.

In this figure, only two modules 51 and 52 have been shown, respectively, but the outline of the module 53 shows that, as can be seen from the preceding explanations, any number of modules can be provided above two.

Each module includes a primary circuit winding 54 and 55 respectively and an individual magnetic circuit 56 and 57.

Each module is supplied from a voltage source 58 connected to two main lines 59 and 60 to each of which are connected the terminals of the two windings 54 and 55.

Each of these terminals 54a and 54b on the one hand, 55a and 55b on the other hand leads to a branch with two branches on each of which is a thyristor, which are mounted head to tail for the same branches: 61 and 62-63 and 64-65 and 66-67 and 6a

These thyristors are controlled by any known electronic means such that in the same given primary winding is sent a current either in one direction or in the other.

It follows that in one case the single secondary winding 70 is the seat of a voltage which, if necessary, is added to the other voltages arising from the other modules, while in the other case no voltage is induced in the secondary winding.

It can thus be seen that, depending on the direction in which the winding is traversed, the induction effect is neutralized.

But, here again, the magnetization of the magnetic circuits is permanent, whatever the effective direction of the current. In other words, the magnetic circuits are always supplied, but the voltage in the secondary winding is either effectively induced or zero.

The electronic solution which has just been described has many advantages among which we can cite the fact that the engagement and the break are made at the zero of the sinusoid so that whatever the combination used for the modules, there is conservation of the pure sinusoidal regime.

In addition, the use of thyristors or transistors to selectively switch modules, makes it possible to obtain extremely high switching speeds, necessary for regulating electrical quantities with very high performance.

Referring now to Figures 5 and 6, we see another embodiment: ion of the invention according to which each module comprises two primary circuit windings.

FIG. 5 shows a complete module 71 and the start of a second 72 with, as always, a single secondary circuit winding 73.

Each module includes a magnetic circuit 74 and two coils of the same pitch, respectively 75 and 76.

A voltage source 77 is connected to two lines 78 and 79, the latter directly leading to one of the terminals 76a of the winding 76 and to the terminal 80a of a connector 80.

Line 78 leads to a branch with two branches, one of which leads to terminal 76b of the winding 76 and the other is connected on the one hand to terminal 75a of the winding 75 and on the other hand, to terminal 81a d a coil 81 whose pitch is opposite to that of the coil 75 and whose second terminal 81b can be connected to line 79, like terminal 75b, depending on the position of the connector 80.

With this arrangement, it can be seen that the current which divides according to the arrows F1 and F2 always flows through the winding 76 and, depending on the position of the connector 80, flows through either the winding 75 or the winding 81.

In the first case a voltage is induced in the secondary winding 73 and this tension is added to the induced voltage of the winding 76 while in the other case the winding 81 having a reverse pitch winding of the winding 75, the induced voltage in the secondary winding 73 is no longer added to but subtracted from the voltage induced from the primary winding 76 so that, ultimately, the secondary winding 73 is traversed either by the nominal voltage of the module 71 or by a zero voltage for the same module 71.

In this case, the secondary winding 73 is traversed, if necessary, by the only voltages induced by the other modules.

Referring now to FIG. 6, we can see an assembly which also includes two primary windings for each module but, here, the neutralization of each module is obtained by different means.

Two complete modules 90 and 91 have been shown and the outline of a third 92.

Each of these two modules comprises a primary winding 93 and 94 associated with a magnetic circuit 95 and 96 and the terminals of which are permanently connected to two lines 97 and 98 supplied by a source 99.

In addition, each of these modules comprises a second winding respectively 100 and 101 associated with a magnetic circuit 102 and 103, all the modules corresponding, as always, to a single secondary winding 104.

Between the lines 97 and 98 on the one hand and the terminals of the windings 100 and 101 on the other hand, there are interposed inverters 105 and 106 respectively.

We understand that with this arrangement, depending on the position that is given to each inverter located in each module, the corresponding winding 100, 101, etc ... is traversed in the same way as the corresponding winding 93, 94, etc. ... or is in opposition so that, as in the case of FIG. 5, the secondary winding 104 is traversed by an induced voltage which is added or subtracted from that, permanent, of the windings 93, 94, etc ...

The voltage across the secondary winding 104 is therefore the result of an addition of the voltages of each activated module.

Referring now to FIG. 7, we see that we have graphically represented the way of dividing the total power P admissible by the secondary winding into modules each having, for a given current, a power which is a regularly declining fraction of the power P.

ou même

ou

etc...This graph tends to show visually that one can easily reach an extreme fineness of adjustment since one could, whatever the power P, provide a last module of power equal to

or even

or

etc ...

This graph also shows that the obtaining of this finesse is done by means of an extremely compact and therefore inexpensive module whereas generally the increase in a given performance is proportionally much more complicated and expensive than the performance itself.

In Figure 8, there is shown schematically a transformer according to the invention comprising four modules of the type according to which each of these comprises two primary windings and two magnetic circuits.

We see that for each module 110, 111, 112 and 113 the two windings respectively 114 and 115, 116 and 117, 118 and 119, 120 and 121 are equal as well as the corresponding magnetic circuits 122 and 123, 124 and 125, 126 and 127, 128 and 129.

It is indeed fundamental that the two primary circuits and the two magnetic circuits of each module are strictly equal so that one can neutralize the other.

It is understood, of course, that the resulting voltage is either zero or equal to the addition of the two primary circuits of each module.

Each module has a binary function, 0 and 1, obtained by inverting the field of one primary with respect to the other.

FIG. 9 shows an example of application of the invention to the regulation of a transformer.

In this diagram, we see five modules 130 to 134 associated with a secondary circuit 135 which itself constitutes the primary circuit of a power transformer comprising, in the known manner, a magnetic circuit 136 and a secondary circuit 137.

FIG. 10 represents a diagram of a variant according to which a branch is connected in the middle of one of the two windings of each module and constitutes the supply of the corresponding winding of the following module.

Thus, for example, the module 140 is supplied with 220 Volts from the source 141 by two main lines 142 and 143. This voltage is applied to the winding 144 associated with a counterpart 145.

From the middle of winding 144, leads a branch 146 which leads to the end of the corresponding winding 147 associated with a counterpart 148 of the following module 149. The other end of winding 147 is connected directly to line 142 of so that the supply voltage for winding 147 is only 110 volts.

In the same way, the winding 150 associated with the winding 151 of the module 152 is supplied with 55 Volts and so on, the secondary 153 being always unique and common to all the modules.

; avec un cou- rant de

pour un courant nominal de i. Le module 149 a et

. Le module 152 a

et

etc...The first module 140 has a power of

; with a current of

for a nominal current of i. Module 149 has and

. Module 152 has

and

etc ...

With this variant, the number of turns of the primary windings is constant for all modules, regardless of their power. In this way, a standardization is achieved which leads to a saving in labor.

On the other hand, savings are made in raw material (copper) since the current in each module has a decreasing value for which the diameter of the winding wire can be exactly adapted. For a set of modules, an excellent match is obtained between the current and the quantity of copper necessary and sufficient.

• - plutôt que d'avoir des dimensions rationnelles, certes, mais peu pratiques comme celles qui sont schématisées sur la figure 7, il est préférable de prévoir pour les circuits magnétiques des dimensions constantes pour ce qui est de la longueur et de la largeur tandis que l'on fait varier seulement l'épaisseur selon la puissance désirée pour chaque module. Ce mode de construction est schématisé par la figure 8. Un exemple chiffré se trouve dans le tableau de la page 8 où la dernière colonne indique l'épaisseur du circuit magnétique en millimètres comme seule dimension variable d'un module à l'autre, la longueur et la largeur étant établies une fois pour toutes.
• - Plutôt que de construire un important transformateur composé exclusivement de modules conformes à l'invention, il est possible d'associer un transformateur banal à un transformateur conforme à l'invention et comportant plusieurs modules de petite puissance, ce transformateur agissant comme régulateur du premier. Une application de ce principe se trouve dans les transformateurs de ligne auxquels on peut adjoindre quelques modules qui régulent automatiquement les variations de tension.
• - La possiblité de combiner un gros; transformateur à tension constante et un transformateur conforme à l'invention à tension réglable, conduit à quatre solutions possibles qui sont respectivement :
  • . la réalisation d'un transformateur complet conforme à l'invention dans une seule structure;
  • . la réalisation dans une première structure d'un trans- ; formateur à tension constante et d'une partie modulaire conforme à l'invention puis, dans une deuxième structure, un ensemble de modules ne servant qu'aux réglages fins de la puissance minimum;
  • . la réalisation dans deux structures différentes d'un transformateur à tension constante et d'un transformateur modulaire conforme à l'invention, ces deux structures étant électriquement connectées;
  • . la réalisation d'un ensemble de régulation comprenant d'une part un transformateur à tension constante aux bornes du secondaire et d'autre part, un transformateur à tension réglable au primaire dans la plage de -15 à + 15%.
  Comme indiqué plus haut, la commande des différents modules peut être obtenue soit par des moyens électro-mé- ; caniques, soit par des moyens électroniques.
• - Lorsque le circuit primaire des modules comporte deux bobinages et deux circuits magnétiques, l'enroulement peut être obtenu soit indépendamment pour chacun d'eux soit en continu pour les deux bobinages en donnant à chaque spire un parcours en 8, -comme cela est schématisé sur la figure 11.
• - Le régime sinusoïdal restant pur à tous les instants, un transformateur selon l'invention permet d'alimenter un redresseur en conservant son ondulation résiduelle naturelle.
• - Il faut noter que la disposition de deux circuits magnétiques avec deux circuits primaires pour chaque module donne des résultats tout à fait différents du montage connu sous le nom de "shunt magnétique" car celui-ci n'a pas d'enroulement primaire. Il en résulte des fuites créant un déphasage courant-tension important d'où un cosinus cp médiocre. Selon l'invention, au contraire, on obtient un cosinus ϕ voisin de 1 avec les réalisationsdu type représenté notamment sur les figures 1 et 8.
• - On peut prévoir un transformateur modulaire conforme à l'invention utilisant des solutions mixtes électro-mécaniques et électroniques notamment en prévoyant des thyristors pour le dernier module seulement, ces thyristors ne jouant que sur une fraction infime de la sinusoïde et ne provoquant une variation de puissance que dans des proportions absolument insignifiantes avec un taux de distorsion très réduit .

The practical details of the construction of a transformer according to the invention are within the reach of those skilled in the art, but the following provisions may however be cited:

• - rather than having rational dimensions, of course, but impractical like those which are shown diagrammatically in FIG. 7, it is preferable to provide for magnetic circuits constant dimensions in terms of length and width while only the thickness is varied according to the power desired for each module. This construction method is shown schematically in Figure 8. A numerical example is found in the table on page 8 where the last column indicates the thickness of the magnetic circuit in millimeters as the only variable dimension from one module to another, the length and width being established once and for all.
• - Rather than building a large transformer composed exclusively of modules according to the invention, it is possible to associate a common transformer with a transformer according to the invention and comprising more several small power modules, this transformer acting as regulator of the first. An application of this principle is found in line transformers to which we can add a few modules that automatically regulate voltage variations.
• - The possibility of combining a big one; constant voltage transformer and a transformer according to the invention with adjustable voltage, leads to four possible solutions which are respectively:
  • . the production of a complete transformer according to the invention in a single structure;
  • . the realization in a first structure of a trans-; constant voltage trainer and a modular part according to the invention then, in a second structure, a set of modules used only for fine adjustments of the minimum power;
  • . the production in two different structures of a constant voltage transformer and a modular transformer according to the invention, these two structures being electrically connected;
  • . the production of a regulation assembly comprising on the one hand a constant voltage transformer at the terminals of the secondary and on the other hand, a voltage transformer adjustable at the primary in the range from -15 to + 15%.
  As indicated above, the control of the various modules can be obtained either by electro-metered means; either by electronic means.
• - When the primary circuit of the modules has two windings and two magnetic circuits, the winding can be obtained either independently for each of them or continuously for the two windings by giving each turn a path in 8, -as shown in figure 11.
• - The sinusoidal regime remaining pure at all times, a transformer according to the invention makes it possible to supply a rectifier while retaining its natural residual ripple.
• - It should be noted that the arrangement of two magnetic circuits with two primary circuits for each module gives results quite different from the assembly known as the "magnetic shunt" because it has no primary winding. This results in leaks creating a large current-voltage phase shift, hence a mediocre cosine cp. According to the invention, on the contrary, a cosine ϕ close to 1 is obtained with the embodiments of the type shown in particular in FIGS. 1 and 8.
• - A modular transformer can be provided in accordance with the invention using mixed electro-mechanical and electronic solutions, in particular by providing thyristors for the last module only, these thyristors acting only on a tiny fraction of the sinusoid and causing a variation in power only in absolutely insignificant proportions with a very reduced distortion rate.

• - A tout instant la charge appliquée au secondaire reste sous tension et, cela, même pendant le temps des interruptions dues aux commutations.
• - La coupure et la fermeture des circuits de mise en action des modules se fait au 0 de la sinusoïde puisque la modification du nombre de modules utilisés a pour conséquence une action sur l'amplitude de la sinusoïde.
• - La surface de fuite est réduite au minimum et est identique à à celle d'un transformateur normal de haute performance et notamment avec des réalisations représentées sur les figures 1 et8.
• - La commutation se fait sans supture de charge.
• - Le réglage se fait selon une progression pas à pas extrêmement fine.
• - On peut utiliser des dispositifs de stabilisation de tous types connus.
• - La puissance est illimitée.
• - Uitransformateur conforme à l'invention a un rendement égal à celui d'un transformateur normal.
• - le réglage se fait sans aucune interruption de l'alimentation électrique.
• - La variation de tension est réalisée à partir d'un système d'asservissement pas-à-pas qui évite une mise à zéro de la tension du secondaire, lorsqu'il faut la moduler.

It emerges from the above description, that the invention makes it possible to produce a transformer with adjustable voltage which includes extremely marked advantages compared with known devices:

• - At all times the load applied to the secondary remains energized, even during the time of interruptions due to switching.
• - The switching off and the closing of the modules activation circuits is done at 0 of the sinusoid since the modification of the number of modules used results in an action on the amplitude of the sinusoid.
• - The leakage surface is reduced to a minimum and is identical to that of a normal high performance transformer and in particular with the embodiments shown in Figures 1 and 8.
• - Switching takes place without overload.
• - The adjustment is made according to an extremely fine step-by-step progression.
• - Stabilization devices of all known types can be used.
• - The power is unlimited.
• - The transformer according to the invention has a yield equal to that of a normal transformer.
• - the adjustment is made without any interruption of the power supply.
• - The voltage variation is carried out using a step-by-step servo system which avoids setting the secondary voltage to zero when it has to be modulated.

The invention is not limited to the embodiments described and shown but on the contrary embraces all variants.

Claims (10)

1- Electric transformer intended to deliver an adjustable electrical quantity, in particular for regulation purposes, characterized in that it comprises on the one hand at least two modules which each comprise at least one primary circuit winding (1 and 2) and which are independent and, on the other hand, a single secondary circuit winding (5) common to all the modules, each of these being associated with means making it possible to neutralize its individual electrical induction in the common secondary circuit winding ( 5), while retaining the activity of the corresponding primary magnetic circuit (3-4). 2- transformer according to claim 1, characterized in that the means are constituted by a connector (7-8) individual to each module and having two positions in one of which the primary circuit winding (1-2) is supplied normally by a nominally constant original voltage and in the other of which the magnetic circuit (3-4) remains activated from the same original voltage but by inducing a zero voltage by subtraction. 3- transformer according to claim 2, characterized in that the two positions of the connector (45 to 50) respectively correspond to the normal supply of the primary circuit winding (17 to 22) and to its short-circuiting. 4- transformer according to claim 1, characterized in that between the supply voltage and each of the two terminals (54a-54b, 55a-55b) of the primary circuit winding (54-55) of each module (51-52 ) are inserted two electronic switches such as thyristors or transistors (61 to 68) mounted head to tail and selectively controlled to ensure the reversal of the supply of said winding (54-55). 5- transformer according to claim 1, characterized in that each module (71) comprises two primary circuit windings (75 and 81) selectively supplied, either to ensure normal induction in the secondary circuit winding (73) or for the neutralize. 6 - transformer according to claim 5, characterized in that the two windings (75 and 81) are in opposite directions, a connector (80) being provided for establishing contact between the original voltage and one or the other of these two windings (75 or 81). 7- transformer according to claim 5, characterized in that the two windings (93-100, 94-101) are in the same direction and in that an inverter (105-106) is interposed between the terminals of a single these windings (100-101) and the original voltage which simultaneously supplies the other winding (93-94). 8- transformer according to claim 1, characterized in that the primary circuit winding (144) of the first module (140) is supplied by the two main lines (142-143) of a voltage source (141) and that the corresponding winding (147-150) of the following modules (149-152) is supplied at one of its ends by one (142) of the two main lines (142-143) and at its other end by a bypass (146 ) from an intermediate point, notably in the middle, from the primary circuit winding (144) of the previous module (140). 9- transformer according to claim 1, characterized in that the modules have a nominal voltage providing with a given current a power which is different for each module, the total of these individual powers being substantially equal to the maximum allowable power for the secondary circuit unique. 10- A transformer according to claim 9, characterized in that the powers of the modules are regular decreasing fractions of the total power and whose denominators are whole powers of two.

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