GB2146492A

GB2146492A - Controllable transformer

Info

Publication number: GB2146492A
Application number: GB08418055A
Authority: GB
Inventors: Eugen Nolle
Original assignee: E Blum GmbH and Co
Current assignee: E Blum GmbH and Co
Priority date: 1983-07-14
Filing date: 1984-07-16
Publication date: 1985-04-17
Also published as: FR2549312B1; IT8421891A1; SE8403689L; DE3423160C2; GB2146492B; DE3423160A1; IT8421891A0; CH668499A5; GB8418055D0; IT1175578B; SE8403689D0; FR2549312A1; NL8402230A

Abstract

A controllable transformer has at least one primary coil (7, 7a, 7b, 7c), one secondary coil (8, 8a) and one control coil (9) each located on a respective core section, in which the alternating voltage from the output of the secondary coil is controlled by the control coil (9) which is energised by direct current. The axes (10, 11, 12) of the windings of the secondary coils (8, 8a) and the control coil (9), and conveniently also of the primary coils 7, 7a, 7b, 7c) are at least approximately parallel. <IMAGE>

Description

SPECIFICATION Controllable, voltage-transforming electric machine The invention relates to a controllable, voltagetransforming electric machine with at least one primary coil, one secondary coil and one control coil, each located on a respective core section, in which the alternating voltage from the output of the secondary coil is controllable by the control coil which is energizable by direct current.

Such electric machines are utilized inter alia in welding technology, for example for regulating the current intensity of electric arc welding equipment.

For this purpose the electric machines of the kind initially referred to are used as a transformer with an adjustable or controllable alternating output voltage.

The primary, secondary and control coil or coils are moveover magnetically coupled with one another via a core which is composed of a ferromagnetic material or materials, such as for example iron. The core is moreover so constructed that it forms at least one magnetic flux which is induced in the core and forms at least one primary circuit which does not extend through a secondary coil for magnetic flux induced in the core by at least one primary coil, as well as at least one control circuit extending through one primary coil and one secondary coil and at least one control circuit extending through a control coil, at least the primary circuit and the control circuit having common core sections which can be premagnetised by the control coils which are subjected to the action of adjustable direct current, so that the permeability for the magnetic flux generated by the primary coils is adjustable in these premagnetised regions. By these means it is possible, with an increase in the premagnetisation, for an ever increasing proportion of the magnetic fluxes which are generated by the primary coils and are caused, while the control coils are deenergised, to flow to a large extent via the primary circuit into the main circuit which contains the secondary coil, so that a likewise increasing output current can be removed from the secondary coil.

Electric machines of the kind initially referred to have already been proposed in which the winding axis of the control coil extends at right angles to the winding axes of the primary and secondary coils.

The core has, moreover, a frame-like core part which forms the main circuit and also forms two core piece zones provided with the primary winding and the secondary winding, as well as two yoke portions connecting the core pieces, and two control cores are provided which are transverse or at right angles to this frame-like core part, forms the control circuit and parts of the primary circuit and each have two outer core piece parts, a middle core piece part and two yoke parts. The two outer core piece parts of the control core moreover are located one on each side of the secondary coil against the core piece parts of the frame-like core partwhich forms the main core and the middle limits of the two control cores extend through a common control coil.

An electric machine constructed in this manner is, however, uneconomic and expensive, since, due to the arrangement of its coils, it necessitates a relatively complicated and uneconomic core construction and the use of a large amount of core material and copperforthe coils. It can also be produced only by the so-called "Lege" technique.

The basic object of the present invention is to provide an electric machine of the kind initially referred to which can be produced and assembled in a particularly simpler, more national and economic manner and furthermore requires a small consumption of material as well as having greater efficiency.

According to the invention this is attained with an electric machine of the kind initially referred to in that (a) the axes of the windings of at least the secondary coil or coils and the control coil or coils are at least approximately parallel, (b) the control coil is arranged between secondary coils or the secondary coil is arranged between control coils and the axes of the windings of at least these coils are at least approximately in one plane and the coils are arranged at least approximately at the same level, i.e. alongside one another, (c) the core sections within the secondary coil or coils can be traversed by the control flux generated by the control coil or coils and by the main flux generated by the primary coil or coils, (d) the axes of the windings of at least one primary coil and at least one secondary coil are approximately in alignment with one another, i.e. they are practically coaxial, and (e) at least one primary coil is arranged so that it is axially spaced apart from at least one secondary coil.

Moreover, it may be advantageous if, according to an additional inventive feature, the core which carries the several coils is so constructed that it forms at least one main circuit on which only the primary and secondary coils are arranged, as well as at least one distribution circuit on which only the primary coil or coils is or are arranged and also at least one control circuit on which only the control coil or coils and the secondary coil or coils are located.

When using several primary coils and/or secondary coils, it may be advantageous, depending on the application, if the primary coil or coils and/or the secondary coil or coils are connected or can be connected in series.

Moreover, it may be appropriate for many applications, if the main circuit is formed essentially as a U-l circuit or as an M circuit or as an E circuit and the control circuit or circuits is or are formed as M circuits. For other applications, it may however, also be advantageous if the main circuit is formed as an N-core having side limbs, in which case the N is equal to 2, and preferably as a 3 U-l core such as is known for example from DIN 41300 or 41302, and the control circuits are formed essentially as M control circuits.

Furthermore, it may be advantageous if the core forms at least one further control circuit on which only one control coil is arranged and if at least the portion of the core on which this control coil is arranged is part of a control circuit on which only one secondary coil is additionally accommodated.

According to a further feature of the invention it may additionally be advantageous if at least the axes of the windings of the control coil or coils and of the primary coil or coils are at least approximately parallel to one another.

A particularly simple and space-saving construction of an electric machine of the kind initially referred to may be obtained if the axes of the windingfs of the control, primary and secondary coil or coils are at least approximately parallel to one another.

The core sections or at least some of them may be at least partly of ferrite cores, e.g. sintered ferrite cores. At least some of the core parts or core part sections may, however, consist instead of thin sheet metal plates which are bonded together, e.g. stuck together. In such cases, it may be advantageous if the thin sheet metal layers of the core parts of core part sections for the primary, secondary and control coils are arranged at least approximately parallel to one another. Moreover, it may also be expedient for the construction of the core to be carried out in such a manner that the planes of the control and primary circuits, which are parallel to the magnetic lines of force, extend at least approximately parallel to each other.

An arrangement of the electric machine which is advantageous from the standpoints of efficiency and construction can be provided if the control coil is located around a core section, which is magnetically shunted by two adjoining core sections which are magnetically coupled to at least one further core section surrounded by at least one secondary coil and if the field of lines of force which can be generated by the control coil can be caused to pass through that core section around which the secondary coil is located An arrangement of the electric machine which is particularly simple and favourable from the standpoint of use of material can be provided of each of the coils is located around one core section composed of bonded together thin metal plates which are magnetically coupled, via the contact surfaces formed on the iron cores, with iron cores disposed transversely to them, which last-mentioned iron cores are also composed of bonded together thin metal plates, in which case it may be advantageous if the iron core sections which are surrounded by the coils constituted lateral core pieces and if the main core sections which are magnetically coupled to them are yokes. Such, lateral core pieces and yokes may particularly advantageously be made in the form square-section stacks of metal laminae which, for example, may consist of individual metal laminae that are stuck together. The use of yokes and lateral core pieces which are composed of stacks of metal laminae ensures simple and economic manufacture as well as economic storage, since such components can be nationally manufactured and assembled and furthermore such individual laminated stacks can be used for various different electric machines.

It may moreover be advantageous if the core of the electric machine comprises two outer yoke cores and two intermediate cores arranged between the latter, a magnetically coupling core piece for a control coil being arranged between the said intermediate cores and furthermore the core pieces for the primary and secondary coils being provided in each case between the outer yoke cores as well as between the intermediate yoke cores.It may also be advantageous if two cores pieces are provided between the outer yoke cores and the intermediate yoke cores, as well as between the intermediate yoke cores, the coils surrounding the core pieces between the intermediate cores being secondary coils and the core pieces provided between the two outer yoke cores and the intermediate yoke cores each having a primary winding and furthermore the core piece which carries the control coil being provided between the two iron cores which carry the secondary coils and between the intermediate yokes.

In an electric machine which is constructed in this manner, two primary circuits are provided for the magnetic fluxes which are induced in the core by the primary coil or by partial windings of a primary coil, which primary circuits are formed by an outer yoke core, an intermediate yoke core and two primary core pieces which magnetically couple these yoke cores and which carry the primary coils or partial windings of a primary coil. The two outer yoke cores also form a part of the main circuit. The main circuit is formed between these outer yoke cores by the primary core pieces that carry the primary coils or the partial windings of a primary coil and furthermore by the secondary core pieces that carry the secondary coils or the partial windings of a secondary coil, as well magnetically couple these yoke cores and which carry the primary coils or partial windings of a primary coil.The two outer yoke cores also form a part of the main circuit. The main circuit is formed between these outer yoke cores by the primary core pieces that carry the primary coils or the partial windings of a primary coil and furthermore by the secondary core pieces that carry the secondary coils or the partial windings of a secondary coil, as well via one intermediate yoke core, a secondary yoke core and thence via the second intermediate yoke core back to the control core piece.

As is clear from the preceding description, lines of force of both a main circuit and also a control circuit can be set up in the core pieces which carry the secondary coils. In order to ensure the best possible manner of operation of an electric machine according to the invention, it is therefore particularly advantageous if the cross-section of the intermediate yoke cores is smaller than that of the core which carries a secondary coil. By means of this feature, it is possible to ensure that, when the electric machine is fully controlled, i.e. when the control coil is completely subjected to the action of direct current, the intermediate yoke cores in the region between the core piece which carries one secondary coil and the core piece which carries the control coil is fully saturated, so that this region is practically impassable by the magnetic flux which is produced buy a primary coil, whereas in the core pieces which carry a secondary coil, due to the greater cross-sectional dimension, the flux density, and thus the magnetic induction and hence also the field strength is much less, so that these core pieces are not saturated and hence have no undesirable effect on the magnetic flux which is caused to flow through a secondary coil and which is induced in the core by a primary coil.It has proved to be particuarly advantageous for the cross-section of the intermediate cores is between 10 and 70%, and preferably between 30 and 60% of the size of the cross section of the core which carries a secondary coil.

Furthermore, it may be advantageous if the cores that carry a primary coil and/or the outer yoke cores have a cross-section which is at least approximately equal in area to that of the cores of the primary and/or secondary cores and it may in addition be advantageous of the core which carries a control coil has a cross-sectional area at least twice as large as that of one of the intermediate yokes cores.

Moreover, it may be appropriate if at least groups of the individual cores are composed of materials of different permeability and it may be advantageous for many applications of the outer yoke cores and/or the cores for the secondary or control cores are composed of material of higher permeability than that of the intermediate yoke cores.

The invention is also suitable in a particularly advantageous way for the construction of electric machines of the kind initially referred to which are of a multiphase type. Thus, it may, for example, be particularly advantageous for a three-phase electric machine, if the core thereof comprises at least two outer yoke cores and at least two intermediate yoke cores arranged between the latter, two outer core pieces and an intermediate core piece arranged between the latter being provided in order to obtain magnetic coupling between the outer yoke cores and the intermediate yoke cores, as well as between the latter, and two core pieces which magnetically couple them together being furthermore provided between the intermediate yoke cores for carrying the control cores, the said two core pieces also being located in each case between the corresponding middle core piece and an outer core piece. Moreover, it may be advantageous if the primary coils are fitted around the outer middle core limbs which are located between the outer and intermediate yoke cores, and the outer core pieces provided between the intermediate yoke cores as well as the middle core piece located between the outer core pieces are provided with the secondary coils.

In order to ensure optimum operation of such an electric machine, it is appropriate to construct the core thereof so that the cross-section of the middle core piece is at least approximately twice as large as that of the outer core pieces and/or that of the outer yoke cores and/or that of the core parts that carry the exciter coils. It has proved to be advantageous if the cross-section of the intermediate yoke cores as between 10 and 80%, and preferably between 30 and 60% of the cross-section of the middle corepiece, so that when the electric machine is completely controlled saturation occurs in the intermediate yoke cores, whereas the full control of the electric machine is only slightly apparent in the middle core piece.

As already mentioned, the yoke cores or the core pieces may be composed of either sintered ferrite, or bonded together stacks of thin metal plates, or of some other ferro-magnetic materials. It may be advantageous if at least some of the yoke cores or yoke core sections are foS integrally with at least some of the core pieces er tore piece secfonst Moreover, at least some of the yoke cores may have core pieces formed thereon or at least some of the core pieces may have yoke cores formed thereon.

It may, however, be advantageous if the core pieces and/or the yoke cores are made of round cross-section.

An advantageous embodiment, in particular for a single-phase core, can be obtained if core pieces for the primary coils are formed on at least one of the outer yokes. The outer core part can then be made U-shaped, the outer limbs of the "U" constituting the lateral core pieces and the connecting limb of the "U" the yoke. In addition, at least one of the intermediate yoke cores may carry core pieces which are at least partly formed thereon. Moreover, it may be advantageous if at least one of the intermediate yoke cores that are employed has at each of its end parts an outer limb and these outer limbs form the outer core pieces, while a middle limb is formed thereon between the outer limbs, so that the said core is thus E-shaped.A construction which is particularly simple from an electrical standpoint is obtained, when two E-shaped cores are arranged in mirror-image relationship to each other, mutually abutting outer limbs and the middle limb forming the core pieces, and in addition two U-shaped cores, the connecting limbs of which form the outer yoke cores and the outer limbs of which forming the core pieces, are also arranged in mirror-image relationships to each other so that they are in surface contact with the intermediate yoke cores by means of the core pieces formed thereon.

Independently of the method of manufacture namely whether the core parts used are produced as a stack of thin metal plates, or made of sintered metal or otherwise, it is advantageous if the portions of the limbs or intermediate limbs or core pieces or yoke core parts which face each other are machined flat, preferably ground or milled.

A core in a three-phase construction may be so arranged that at least one of the yoke cores has two outer limbs and a middle limb formed thereon and thus forms an E-shaped core part. At least one of the core parts which comprises the intermediate yoke may be made E-shaped and may have further intermediate limbs formed between the outer and middle limbs of the "E", which further intermediate limbs form at least parts of further core pieces. An optimum constructional form of such an electric machine includes two E-shaped core parts formed with further intermediate limbs, each of which and each comprising the intermediate yoke, these core parts being arranged in mirror-image relationship to each other and with respect to the connecting limbs which constitute the intermediate yokes, and the outer E-shaped core parts, which are also arranged in mirror-image relationships to each other, abut by means of their outer limbs and then intermediate limbs against the intermediate yoke cores.

A symmetrical construction which has moreover proved to be particularly favourable, is one in which the outer and/or middle andlor intermediate limbs are at least approximately half as long as the core pieces.

The invention will be explained in greater detail with reference to Figures 1 to 6, in which: Figure 1 shows a core in elevation with the various coils arranged thereon in section for an electric machine according to the invention in a single-phase embodiment, Figure2 shows a plan view of Figure 1, Figure 3 shows a core in elevation with the various coils arranged thereon in section for an electric machine according to the invention in a three-phase embodiment, Figure 4 shows a plan view of Figure 3, Figure 5shows an embodiment similar to Figure 1, Figure 6shows an embodiment similar to Figure 3, Figure 7shows a further embodiment of a core for an electric machine according to the invention in a single-phase embodiment.

The core shown in Figures 1 and 2 has two outer yoke cores 2 and 2a as well as two intermediate yoke cores 3 and 3a which are magnetically coupled respectively to the directly adjacent outer yoke cores 2 and 2a via two lateral core pieces 4, 4a and 4b, 4c.

Between the intermediate yoke cores 3 and 3a there are provided further lateral core pieces 5 and 5a as well as a lateral core piece 6 arranged between the latter.

The outer yoke cores 2, 2a, the intermediate yoke cores 3, 3a as well as the several lateral core pieces 4, 4a, 4b, 4c, 5, 5a and 6 each consist in this case of a plurality of individual thin metal plates which are glued together.

The several core parts 2, 2a, 3, 3a, 4, 4a, 4,o, 4c, 5, 5a, 6 5a, 6 that form the iron core 1 are moreover as arranged that the individual laminae thereof extend parallel to one another.

At least some of the individual core parts may, however, be composed at least partly of some other material e.g. of sintered ferrite.

In order to obtain the best possible electromagnetic values, the abutting areas at which the individual core parts 2, 2a, 3, 3a, 4, 4a, 4b, 4c, 5, 5a are located opposite and in contact with one another are machined, e.g. ground Series-connected partial windings or fractional coils 7, 7a, 7b, 7c of a primary winding surround the lateral core pieces 4, 4a, 4b, 4c respectively. The lateral core pieces 5 and 5a are surrounded by a secondary winding which is subdivided into two partial windings or fractional coils 8 and 8a. The lateral core piece 6 receives the control coil 9.

As is apparent, the fractional coils 7, 7a, 7b, 7c of the primary winding as well as the fractional coils 8, 8a of the secondary winding and the control coil 9 are so arranged that the centra! axes 10,11 and 12 of the windings are parallel to one another and, as is clear more particularly from Figure 2, they are arranged in one and the same plane which also extends parallel to the individual laminae of the several core parts 2, 2a, 3, 3a, 4, 4a, 4b, 4c, 5, 5a, 6.

Furthermore, as is apparent from Figure 1,the control coil 9 is arranged between the two secondary windings 8, 8a and is of the same height as the latter.

Moreover, the fractional primary windings 7, 7b and 7a, 7c are arranged in coaxial spaced apart relationship with respect to the secondary windings 8 and 8a.

The core 1 forms for the magnetic fluxes induced by the partial windings 7, 7a, 7b, 7c of the primary coil, which are subjected to the action of alternating current, two primary circuits 14, 14a that are indicated in chain-dotted lines in Figure 1 and which are each formed by an outer yoke core 2 or 2a, an intermediate yoke core 3 or3a and two lateral core pieces 4, 4a or 4b, 4c which couple the latter together and receive the fractional windings 7, 7a or 7b, 7c respectively.

The two outer yoke cores 2 and 2a of the iron core 1 moreover form parts of an essentially U-l-shaped main circuit 15forthe magnetic fluxes which are induced by the fractional windings 7,7a,7b,7cofthe primary coil. This main circuit 15 is indicated by a broken line in Figure 1.Between the outer yoke cores 2 and 2a the main circuit is formed by the lateral core pieces 4, 4a, 4b, 4c which carry the fractional windings 7, 7a, 7b, 7c of the primary coil, as well as by the lateral core pieces 5 and 5a which carry the fractional coils 8, 8a of the secondary coil, and furthermore by the portions of the intermediate yoke cores 3 and 3a which are flanked by the mutually confronting contact surfaces of the lateral core pieces 4, 4a, 4b, 4e which carry the primary partial windings and of the lateral core pieces 5, 5a which carry the secondary partial windings.

The two intermediate cores 3 and 3a moreover form parts of an essentially M-shaped control circuit which is divided into two partial control circuits 16, 16a indicated by double dotted chain lines in Figure 1. The partial control circuits 16, 16a moreover extend, starting from the lateral core piece 6 which carries the control coil 9, via one intermediate yoke core 3, one of the lateral core pieces 5 and 5a carrying the fractional coils 8 or 8a and from this lateral core piece 5 or 5a via the other intermediate yoke core 3a back to the core side piece 6 of the control coil 9.

In view of the iron core, the lines of magnetic force of the control, primary and main circuits extend in planes which are disposed parallel to one another.

The intermediate yoke cores 3 and 3a have a smaller cross-section than the other core parts 2, 2a, 4, 4a, 4b, 4c, 5, 5a, 6 which, in the embodiment illustrated, has an area mounting to 50% of the cross-sectional area of the core parts 2, 2a, 4, 4a, 4b, 4c,5,5a,6.

Depending upon the circumstances that will obtain when it is in use, the core 1 may be composed of core parts of the same permeability or of core parts of different permeability, in which case the intermdiate yoke cores 3, 3a may be made of a material of lower permeability than the material of the other core parts 2, 2a, 4, 4a, 4b, 4c, 5, 5a, 6.

In the following the operation of an electric machine according to Figures 1 and 2 will be explained in greater detail.

When the control coil 9 is not energised, the magnetic fluxes corresponding to the primary cir cuits 14, 14a that are induced in the core 1 extend through the partial windings 7, 7a, 7b, 7c of the primary coil, that is to say the magnetic fluxes do not pass through the partial windings 8 and 8a of the secondary coil but travel along the path of least resistance, namely through the intermediate yoke cores 3 and 3a.

If direct current is now applied to the control coil 9, partial magnetic fluxes corresponding to the two partial control circuits 16 and 16a will be generated, which partial magnetic fluxes will magnetise the parts of the core 1 traversed by them, this magnetisation being dependent on the direct current applied to the control coil 9, that ius to say the greater the applied voltage, so much the greater is the magnetisation.

Such a magnetisation has the effect that, due to the smaller cross-section of the intermediate yoke cores 3 and 3a, a sufficiently greater magnetic induction or flux density is available in the parts of the intermediate yoke cores 3 and 3a which are indicated by cross-hatching in Figure 1 for these parts to become partially saturated, so that a part of the magnetic fluxes induced in the core 1 by the partial windings 7, 7a, 7b, 7c ofthe primary coil can be forced to flow through partial windings 8, 8a of the secondary coil. It is also possible by varying that level of saturation in the parts indicated by crosshatching to cause a more or less small fraction of the magnetic fluxes induced by the primary winding to flow through the secondary winding.As soon as the parts of the intermediate yoke cores 3 and 3a indicated by the cross-hatched areas are fully saturated, they are practically impassable by the magnetic fluxes induced by the partial windings of the primary coil, so that these magnetic fluxes are caused to flow exclusively through the partial windings of the secondary coil.

The core 100 shown in Figures 3 and 4, which is intended for use in an electric machine of a threephase embodiment, has two outer yoke cores 102 and 102a as well as two intermediate yoke cores 103 and 103a arranged between the latter, the intermediate yoke cores 103 and 103a being magnetically coupled together by two outer lateral core pieces 105 and 105a as well as by a middle core piece 105b and core pieces 106, 106a provided between the middle core piece 105b and the outer lateral core pieces 105 and 105a and carrying control coils 109 and 109a respectively. The outer lateral core pieces 105 and 105a, and the middle core piece 105b provided between them carry the secondary windings 108, 108a, 108b which are each provided for one phase.

Each of the inter yoke cores 103 and 103a is moreover magnetically coupled to the outer yoke core 102 or 1 02a adjoining it via two outer core pieces 104, 1 04a or 1 04b, 1 04c as well as by a middle core piece 1 04e or 104f. The core pieces 104, 1 04a, 104b, 104c, 104e and 104f carry respectively partial windings 107, 107a, 107b, 107c, 107e and 107fofthe primary coils, the partial windings 107, 107b or 107a, 107cor107e, 107e,107feach form the coil for a primary phase.

As a result of the construction of the core, the control winding 109 is arranged between the two secondary windings 108, 1 08b, the secondary windings 108, 1 08b, 1 08a and the control windings provided between them being arranged moreover at the same level. In addition the partial primary windings 107, 107b are arranged in coaxially spaced apart relationship with respect to the secondary winding 108b located between them and the partial primary windings 107a, and likewise arranged with respect to the secondary winding 1 08a located between them.

In this embodiment also the core parts that form the core 100 are composed of a plurality of individual thin metal plates which are stuck together and these core parts are also so arranged that the individual metal plates thereof are disposed parallel to one another.

Due to the special construction of the core 100, the central axes 117,118,119, 120 and 121 ofthe windings of the individual coils extend parallel to one another and, as is apparent more particularly from Figure 4, are disposed in a common plane.

As is apparent from Figure 3, the middle core pieces 104a, 105b, have a cross-section which is greater than that of the outer core pieces 104, 104a, 105,105a,104b,104c,andgreaterthanthatofthe core pieces 106, which carry the control coils 109, 109a. Moreover, it can be seen from Figure 3 that the intermediate yoke cores 103, 1 03a have a cross-section which is smaller than that of the other core parts, the cross-section of the intermediate yoke cores 103, 103a in the embodiment shown being about 40% of that of the middle yokes 104e,105b, 104f.

The cross core 100 forms four primary circuits 114, 1 14a, 1 14b, 1 14c, as indicated in chain-dotted lines in Figure 3, for the magnetic fluxes induced by the partial windings of the primary coil which are subjected to the action of alternating current. It also forms two main circuits 115 and 115a which are indicated in broken lines as well as control circuits or partial control circuits 116, 116a, 116b, ll6cforthe magnetic fluxes induced by the control coils 109, 109a. The control or partial control circuits 116, 116a, 116b, 116c, are indicated in double dotted chain lines in Figure 3.As is also apparent from Figure 3, the various core parts or core sections which form the two main circuits 115, 115a constitute a 3 U-l-shaped total main circuit, that is to say a total main circuit which is formed by three limbs interconnected by yokes. The several core parts or core sections which form the partial control circuits are so arranged that they each form an M-shaped control circuit between a respective pair of adjacent limbs of the 3 U-lshaped total main circuit, namely on the one hand the M-shaped control circuit which is formed by the two partial control circuits 116, 11 6a and on the other hand the M-shaped control circuit which is formed by the two partial control circuits 116b, 116c.

The manner in which an electric machine according to Figures 3 and 4 operates corresponds in principle to that of the electrical machine shown in Figures 1 and 2. Also, with an electric machine according to Figures 3 and 4 a more or less large part of the magnetic flux induced in the core 100 by the primary windings can be made to flow through the secondarywindings 108, 108a, 108b since there- gions indicated by the cross-hatching in Figure 3 are more or less magnetised by the control coils 109, 1 09a which are subjected to the action of direct current.

The core parts of the electrical machines according to Figures 1 to 4 may be made of materials other than thin metal plates which are bonded together, e.g. of square ferrite bodies or hexahedrons.

Furthermore, it may be advantageous if at least some individual bodies have a round cross-section.

The embodiments shown in Figures 5 and 6 show iron cores having a shape other than square, namely with the lateral core pieces formed on the yoke cores. These core pieces can be produced in a particularly simple manner making use of the ferrite technique or alternatively they can be formed of thin metal plates which are suitably punched out and bonded together.

Figure 5 shows a single-phase and Figure 6 a three-phase electric machine.

As in Figure 1, the core 201 of Figure 5 has two outer yoke cores 202 and 202a and two intermediate yoke cores 203 and 203a. These intermediate yoke cores are each magnetically coupled to the respective adjacent outer yoke cores 202 or 202a via two lateral core pieces 204, 204a or 204b, 204c formed on the outer yoke cores. The yoke cores 202, 202a, which are formed integrally with the lateral core pieces 204, 204a or 204b, thus form U-shaped core parts 201a, 201 b, the lateral core pieces 204, 204a or 204b, forming the outer limbs of the "U" and the outer yoke cores 202 and 202a forming the connecting portions thereof.The U-shaped core parts 201 a, 201b are arranged in mirror-image relationship to each other and are in contact with the intermediate yoke cores at suitable joint areas.

The core pieces 205, 206 and 205a provided between the intermediate yoke cores 203, 203a are each formed on one of the intermediate yoke cores 203, 203a halfway along the latter, so that E-shaped core parts 201 c and 201 dare produced. Thus, the core pieces 2051, 205al or 2052, 205a2 form the outer limbs, the core pieces 2061 or 2062 form the middle limbs and the yokes 203, 203a form the connecting limbs of the "E". The two E-shaped parts 201 c and 20ldare arranged in mirror-image relationship to each other and are in contact with each other via the contact surfaces formed on their outer and middle limbs. These contact surfaces are advantageously machined so as to make them flat, e.g. they are milled or ground.

Since the remaining parts, such as the coils, and the arrangements thereof etc. in the core of the electric machine shown in Figure 5 are practically identical to those according to Figure 1, the same reference numerals are used for those parts and practically the same manner of operation is obtained as that which is described with reference to Figures 1 and 2.

The core 300 shown in Figure 6 for the electric machine illustrated thereby in a three-phase embodiment has two outer yoke cores 302, 302a as well as two intermediate yoke cores 303, 303a.

The yoke cores 302, 302a have core pieces 304, 304e and 304a, as well as core pieces 304b, 304fand 304e formed thereon so that the yoke cores 302, 302a form the connecting part, the outer core pieces 304, 304a or 304b, 304c form the outer projecting limbs and the core pieces 304e, 304fform the middle projecting limbs of the E-shaped core members 300a and 300b. These two E-shaped core members are arranged in mirror-image relationship to each other and their projecting limbs are in contact with the intermediate yoke cores 303, 303a via contact surfaces.

Core pieces 305, 306, 305b, 306a and 305a are provided between the intermediate yoke cores 303 and 303a, one of these yoke cores 303, 303a being formed in each case on the halves of these core pieces. Moreover, the core pieces 305',3052 and 305a' and 305a2 constitute the outer limbs, the middle core pieces 305b',305b2 constituting middle limbs and the yokes which are formed integrally therewith constitute the connecting part of the E-shaped iron cores 300c and 300e. Further intermediate core pieces 3061, 3062 and 306a', 306a2 are provided between the outer and middle limbs of the E-shaped body and are each formed integrally on the intermediate yoke cores 303 and 303a located opposite them.The cores 303c and 303dwhich are formed in this manner are also arranged in mirrorimage relationship to each other and are in contact with each other via contact surfaces formed on the core pieces 3051,3052, 3061,3062, 305b1, 305,b1, 306a', 306a2, 305a', 305a2. Since the remaing parts function in practically the same manner as those of the electric machine of Figures 3 and 4, the rest of the reference numerals are identical with those of Figures 3 and 4.

The core 400 shown in Figure 7 for an embodiment in the form of a simple-phase electric machine has two outer yokes cores 402, 402a as well as two intermediate yoke cores 403,403a arranged between them. Each of the intermediate yoke cores 403, 403a is magnetically coupled to the outer yoke core 402 or 402a adjacent thereto via two outer core pieces 404, 404a or 404b, 404c as well as by a middle core piece 404e or 404f. Moreover, the intermediate yoke cores 403 and 403a are magnetically coupled together by two outer core pieces 405 and 405a, as well as by a core piece 406, 406a provided between the middle core piece 405b and one of the outer core pieces 405, 405a.The middle core pieces 404e, 404fcarry partial windings 407,407a of a primary winding and the core piece 405b provided between the intermediate yoke cores 403 and 403a carries a secondary winding 408. The core pieces 406 and 406a carry control coils 409 and 409a respectively.

The iron core 400 forms, for the magnetic fluxes induced by the partial windings 407, 407a, which are subjected to the action of alternating current, four primary circuits 414,41 4a, 41 4b, 41 4c which are indicated in chain-dotted lines in Figure 7, as well as two main circuits 415, 415a which are indicated in broken lines and also control or partial control circuits 416, 416a, 416b, 416e for the magnetic fluxes induced by the control coils 409, 409a. The control or partial control circuits 416,41 6a, 41 6b, 41 6c are indicated by double dotted chain lines in Figure 7.

As can be ascertained from Figure 7, the magnetic flux generated by a control coil 409 or 409a can follow two paths, namely along the paths formed by the partial control circuits 416,416a for the partial fluxes induced by the control coils 409 and along the paths formed by the partial control circuits 41 6b, 416e for the partial fluxes induced by the control coil 409a. Moreover, it is clearthat only one control coil 409, 409a is provided for each of the partial control circuits 416, 416c, whereas both a control coil 409 or 409a and also the secondary coil 408 are provided for the partial control circuits 416a, 4166.

The invention is not limited to the embodiments shown. Thus, it also includes yoke cores and core pieces and parts thereof which are differently subdivided and constructed, as well as the use of materials other than those described within the scope covered by the invention.

Claims

1. Controllable, voltage-transforming electric machine with at least one primary coil, one secondary coil and one control coil each located on a respective core section, in which the alternating voltage from the output of the secondary coil is controllable by the control coil which is energizable by direct current and furthermore the core forms at least one main circuit on which the primary and secondary windings are arranged, as well as control circuit on which the control winding or windings are arranged, characterised in that a) the axesofthewindings (10,11,12,117,118, 119,120,121) of at least the secondary coil or coils (8, 8a; 108, 108a, 108b; 408) and the control coil or coils (9; 109, 109a;; 409, 409a) are at least approximately parallel to one another, b) the control coil (9; 109, 109a) is provided between secondary coils (8, 8a; 108, 108a, 108b; 408) or the secondary coil (108b,408) is provided between control coils (109, 1 09a; 409, 409a) and the axes ofthewindings (10,11,12; 117,118,119,120, 121) of at least these coils are at least approximately in one plane (13, 113) and the coils are arranged alongside one another at approximately at the same level.

c) the core sections (5, 5a, 105, 105a, 105b; 405b) within the secondary coil or coils (8, 8a; 108, 108a, 1 08b; 408) can be traversed by the control flux (16, 168;116,1168,116b,116c;4168,416b)generatedby the control coil or coils (1; 109, 109a; 409, 409a) and by the main flux (15; 115,115a; 415,415a) generated by the primary coil or coils (7, 7a, 7b, 7c; 107, 107b, 107e, 107f, 107a, 107c; 407,407a), d) the axe sof the windings (10,11;;117,118,119) of at least one primary coil and of at least one secondary coil are in alignment with one another and e) at least one primary coil (7,7a,7b,7c; 107, 107b, 107e, 107f, 107a, 107c; 407, 407a) is arranged so that it is axially spaced apart from at least one secondary coil (8,8a; 108,108a,108b; 408).

2. Controllable, voltage-transforming electric machine in particular according to claim 1, characterised in that the core (1, 100,400) forms at least one main circuit (15; (15115,1 15a; 415, 415a) on which only the primary (7,7a,7b,7c; 107, 107,b, 107e, 107f, 107a, 107c; 407,407a) and secondary coil or coils (8, 8a; 108, 108a, 108b, 408) are arranged, as well as at least one distribution circuit (14, 14a; 114, 1 14a, 1 14b, 11 4c; 414, 414a, 414b, 41 4c) on whIch only the primary coil or coils (7,7a,7b,7c; 107, 107b, 1 07e, 107f, 107a, 107c; 407, 407a) are arranged and furthermore at least one control circuit (16, 116, 1 16a, 1 16b, 1 16c; 416a, 41 6b) on which only the control coil or coils (109, 109a; 416a,416b) on which only the control or coils (109, 109a, 409, 409a) and the secondary coil or coils (8, 8a; (8,88108, 108a, 108b; 408) are located.

3. Controllable, voltage-transforming electric machine according to claim 1 or 2, characterised in that at least some primary coils (7, 7a, 7b, 7c; 107, 107,o, 107e, 107f, 107a, 107c; 407, 407a) are connected in series.

4. Controllable, voltage-transforming electric machine according to one of claims 1 to 3, characterised in that at least some secondary coils are connected in series.

5. Controllable, voltage-transforming electric machine according to one of claims 1 to 4, characterised in that the main circuit (15115, 11 spa; 415, 415a) is formed essentially as a U-l circuit or as M- or E-l circuit and the control circuits (16 + 16a; 116 + 116a,116b+ 116c;416+416a,416b+416c)are formed as M-circuits.

6. Controllable, voltage-transforming electric machine according to one of claims 1 to 5, characterised in that the main circuit (15; 115 + 115a; 415 + 415a) is formed as an N side-limb core (N > 2), preferably as a 3U-I core (Figures 3,4, 6 and 7) and the control circuits are formed essentially as M controlcircuits(16+ 16a; 116,116a,116b+ 116c; 416 + 416a,416b + 416c).

7. Controllable, voltage-transforming electric machine particularly according to claim 1, characterised in that the core forms at least one further control circuit on which only one control coil is arranged and that at least the portion of the core on which this control coil is arranged is part of a control circuit on which only one secondary coil is additionally accommodated (Figure 7).

8. Electric machine according to one of claims 1 to 7, characterised in that the winding axes of the control coil or coils and of the primary coil or coils are at least approximately parallel to one another.

9. Electric machine according to one of claims 1 to 8, characterised in that the winding axes of the control coil or coils of the primary coil or coils and of the secondary coil or coils are at least approximately parallel to one another.

10. Electric machine according to one of claims 1 to 9, characterised in that some of the core parts or core sections consist of ferrite cores, e.g. sintered ferrite cores (Figures 5, 6).

11. Electric machine according to one of claims 1 to 10, characterised in that at least some of the core parts or core sections are composed of thin metal plate layers which are preferably bonded together.

12. Electric machine according to one of claims 1 to 11, characterised in that at least some of the core sections are composed of thin metal plate layers and at least one ferrite constituent.

13. Electric machine according to one of claims 1 to 12, characterised in that, when core sections of thin metal plate layers are used, they are arranged at least approximately parallel to one anotherforthe primary and/or the secondary andlor the control coils.

14. Electric machine according to one of claims 1 to 13, characterised in that the winding axes of the primary, secondary and control coil or coils are disposed at least approximately in one and the same plane.

15. Electric machine according to one of claims 1 to 14, characterised in that the planes of the conrol and primary circuits, which are parallel to lines of magnetic force, extend at least approximately parallel to one another.

16. Electric machine according to one of claims 1 to 15, characterised in that the control coil is located around a core section which is magnetically shunted by two adjoining core sections which are magnetically coupled to at least one further core section surrounded by at least one secondary coil and that the filled of lines of force which can be generated by the control coil can be caused to pass through that core section around which the second winding is located.

17. Electric machine according to one of claims 1 to 16, characterised in that each of the coils is applied around one core section composed of bonded together thin metal plates which are magnetically coupled via the contact surfaces formed on the iron core sections with iron core sections disposed transversely to them, which lastmentioned iron core sections are also composed of bonded together thin metal plates.

18. Electric machine according to one of claims 1 to 17, characterised in that the core sections which are surrounded by the coils constitute lateral core pieces and the core sections which are magnetically coupled to them are yokes.

19. Electric machine according to one of claims 1 to 18, characterised in that the core comprises two outer yoke cores and two intermediate yoke cores arranged between the latter and a magnetically coupling core piece for a control coil is arranged between the said intermediate yoke cores and furthermore the core pieces for the primary coils and the secondary coils are provided in each case between the outer yoke cores and the intermediate yoke cores as well as between the said intermediate yoke cores.

20. Electric machine according to claim 19, characterised in that two core pieces are provided between the outer yoke cores and the intermediate yoke cores, as well as between the intermediate yoke cores, the coils surrounding the core pieces between the intermediate yoke cores being secondary coils and the core pieces provided between the two outer yoke cores and the intermediate yoke cores each having a primary winding and thatthe core piece which carries the control coil so provided between the two iron cores which carry the secondary coils and between the intermediate yokes.

21. Electric machine according to one of claims 1 to 20, characterised in that the cross-sectional area of the intermediate yoke cores is smaller than that of the cores that carry the secondary coils.

22. Electric machine according to one of claims 1 to 21, characterised in that the cross-sectional area of the intermediate yoke cores amounts to between 10 and 70%, and preferably between 30 and 60%, of that of the cores that carry the secondary coils.

23. Electric machine according to one of claims 1 to 22, characterised in that the cores that carry the primary coils have at least approximately the same sized cross section as the cores of the secondary coils.

24. Electric machine according to one of claims 1 to 23, characterised in that the outer yoke cores have a cross-section at least approximately equal in size to that of the cores that carry the secondary coils.

25. Electric machine according to one of claims 1 to 24, characterised in that the core that carries the control coil has a cross-section which is at least approximately twice as large as that of one of the intermediate yoke cores.

26. Electric machine according to one of claims 1 to 25, characterised in that at least groups of the individual cores are composed of material of different permeability.

27. Electric machine according to claim 26, characterised in that the outer yoke cores and/or the cores for the secondary or control coils are composed of material of higher permeability than that of the intermediate yoke cores.

28. Electric machine according to at least one of the preceding claims, characterised in that the core of the electric machine comprises at least two outer yoke cores and at least two intermediate yoke cores arranged between the latter, two outer core pieces and an intermediate core piece arranged between the latter being provided in order to obtain magnetic coupling between the outer yoke cores and the intermediate yoke cores as well as between the latter, and two core pieces which magnetically couple them together and being furthermore provided between the intermediate yoke cores for carrying control cores, the said two core pieces being located in each case between the corresponding middle core piece and an outer core piece.

29. Electric machine according to claim 28, characterised in that primary coils are fitted round the outer and middle core limbs which are located between the outer yoke cores and the intermediate yoke cores, and the outer core pieces provided between the intermediate yoke cores as well as the middle core piece provided between the said outer core pieces are provided with secondary coils.

30. Electric machine according to one of claims 28 or 29, characterised in that the cross-section of the middle core piece is at least approximately twice as large as that of the outer core pieces and/or that of the outer cores and/or that of the core parts that carry the exciter coils.

31. Electric machine according to one of claims 28 to 30, characterised in that the cross-section of the intermediate yoke cores is between 10 and 80%, and preferably between 30 and 60% of the cross-section of the middle core pieces.

32. Electric machine according to one of the preceding claims, characterised in that at least some of the yoke cores or yoke core sections are formed integrally with at least some of the core pieces or core piece sections (Figures 5, 6).

33. Electric machine according to claim 32, characterised in that at least some of the yoke cores have core pieces formed thereon (Figures 5, 6).

34. Electric machine according to claim 32 or 33, characterised in that at least some of the core pieces have yoke cores formed thereon.

35. Electric machine according to one of claims 32 to 34, characterised in that square or cylindricalsection yoke cores have core pieces of like section formed thereon (Figures 5, 6).

36. Electric machine according to one of claims 32 to 35, characterised in that core pieces for the primary coils are formed on at least one of the outer yokes (Figures 5,6).

37. Electric machine according to at least one of claims 32 to 36, characterised in that at least one core part is made U-shaped, the outer limbs of the U constituting the lateral core pieces and the connecting limb the yoke (Figure 5).

38. Electric machine according to at least one of claims 32 to 37, characterised in that at least one of the intermediate yoke cores carries core pieces which are at least partly formed thereon (Figures 5, 6).

39. Electric machine according to at least one of claims 32 to 38, characterised in that at least one of the intermediate yoke cores has at each of its end parts an outer limb, which outer limbs form the outer core pieces, and between which outer limbs a middle limb, the said core thus being E-shaped (Figure 5).

40. Electric machine according to at least one of claims 32 to 39, characteristed in that two E-shaped cores are arranged in mirror-image relationship to each other, the mutually abutting outer limbs and the middle limbs forming the core pieces.

41. Electric machine according to at least one of claims 32 to 40, characterised in that two U-shaped cores, the connecting limbs of which form the outer yoke cores and the outer limbs thereof the core pieces are arranged in mirror-image relationships to each other and are in surface contact with the intermedate yoke cores by means of the core pieces formed thereon.

42. Electric machine according to at least one of claims 32 to 41, characterised in that at least one of the yoke cores has two outer limbs and a middle limb and thus forms an E-shaped core part.

43. Electric machine according to at least one of claims 32 to 42, characterised in that at least one of the core parts, which comprises the intermediate yoke is made E-shaped and further intermediate limbs are formed thereon between the outer limbs and the middle limbs, which further intermediate limbs form at least parts of further core pieces.

44. Electric machine according to at least one of claims 32 to 43, characterised in that two E-shaped core parts with additional intermediate limbs, each of which core parts comprise an intermediate yoke, are arranged in mirror-image relationship to each other and with respect to the connecting limbs which constitute the intermediate yokes, while the outer E-shaped core parts which are also arranged in mirror-image relationship to each other, abut by means of them outer limbs and then intermediate limbs against the intermediate yoke cores.

45. Electric machine according to at least one of claims 32 to 44, characterised in that the outer limbs which are formed in the intermediate yokes and/or the middle limbs and/orthe intermediate limbs are at least approximately half as long as the core pieces.

46. Electric machine according to at least one of the preceding claims, characterised in that the parts of the limbs or intermediate limbs or of the core pieces which are directed towards each other, are machined flat, and preferably ground or milled (Figures 5,6).