Controllable transformer The present invention relates to a variable transformer/frequency converter device comprising a body of a magnetic material, a primary winding (or first main winding) wound round the body about a first axis, a secondary winding (or third main winding) wound round the body about a second axis at right angles to the first axis, and a control winding (or second main winding) wound around the body about a third axis, coincident with the first axis.

The invention is also related to a method for controllable conversion of a primary alternating current/voltage to a secondary alternating current/voltage by the use of a device comprising a body of a magnetic material, a primary winding (or first main winding) wound round the body about a first axis, a secondary winding (or third main winding) wound round the body about a second axis at right angles to the first axis, and a control winding (or second main winding) wound around the body about a third axis, coincident with the first axis. The method according to the invention is characterised in that it comprises the following steps: - feeding the primary winding with a primary alternating current/voltage, - feeding the control winding with an alternating voltage which is either in phase or phase shifted 180° relative to the primary current/voltage, - feeding the control winding with a variable current, and thereby controlling the transformer's conversion ratio by means of the variable control current.

The transformer device is preferably designed as a hollow magnetisable core with an internal winding compartment for internal windings and an external winding compartment for external windings. In a preferred embodiment it comprises 3 windings, a primary winding in the external winding compartment with associated control winding in the internal winding compartment, and a secondary winding in the internal winding compartment.

The windings in the external winding compartment and the windings in the internal winding compartment are aligned at right angles (perpendicular) to each other in the compartment, thereby creating magnetic fields that are orthogonal. The internal winding compartment may of course house the primary winding and the external winding compartment may house the secondary winding and the control winding. The frequency converter is specially, but not in a limiting manner, intended for use in the MVA range.

The invention is a further development of the device set forth in PCT/NO01/00217, which is hereby included in the present invention in its entirety.

In this description the expressions"primary winding"and"secondary winding"are used to design a winding where energy is input (primary) and a winding which is meant for connection to a load (secundary) as is usual in transformators. In the device according to the invention the primary and the secundary windings are wound round orthogonal axes. The expression "control winding"denotes a winding which controls the tranformer's tranformation ratio.

A transformer comprising orthogonal windings is previously known from US patent 4,210, 859, Meretsky et al. of April 18,1978. However, the known solution manifests several disadvantages. The main aspects of the invention will be described below based on the prior art described in said publication.

In US patent 4,210, 859 a device is described which is developed on the basis of a test conducted on a ferrite pot core with dimensions 18xl lmm, and with current levels in the mA range. Ferrite, however, is not suitable for use at high power levels, due amongst other things to the substantial costs involved.

This is on account of the fact that the size of a ferrite core is limited purely from the production engineering point of view and because higher power levels can be transferred by increasing the frequency of the voltage that has to be converted, but this in turn leads to complicated and expensive power electronics. The invention is on the contrary aimed at the use of core plate, which has special properties with regard to permeability, these properties being employed in the invention. Fig. 6h illustrates the linear part of the magnetisation curve for a standard commercial core plate. In an embodiment of the invention a laminar material is used where the magnetisation curve is the same for all directions in the plate. This involves the use of non- directional plate without this being considered as limiting for the application, since for some applications it may be advantageous to have a directionally oriented plate.

US patent 4,210, 859 illustrates a connection diagram for a variable transformer solution with 4 windings: a primary main-winding, a secondary main winding arranged at right angles to the primary winding and two control windings, one for each main winding. The mode of operation is such that a

variable DC current in both control windings will result in a transfer of AC voltage from the primary to the secondary winding. A transformer of this kind cannot be considered a realistic option, particularly if the area of application is outside the mA range, because a DC current in the control windings will rotate the domains in the magnetic material in an unfavourable direction for connection in one half cycle of the primary voltage, causing harmonics in the secondary voltage. This phenomenon, which has been extensively studied by the inventors is not taken into consideration in US patent 4, 210, 859.

In the present application figs. 6c to 6d illustrate said rotation of the domains. In these figures, Vp represents a voltage on the primary winding and Vs a voltage on the secondary winding. At the same time Vp denotes the winding axis of the primary winding and Vs the winding axis of the secundary winding. Flux produced or linked by the primary winding will then have the direction of Vp while flux produced or linked by the secundary winding will have the direction of Vs. In fig. 6c the domains are aligned according to the primary voltage Vp and their magnetisation B will vary roughly as shown in the figure. The magnetic field H produced by this priomary winding will vary from positive to cero and from cero to a negative value.

The phase shift of the magnetisation in relation to the primary voltage is not included here in order to simplify the illustration, (the magnetisation current lags 90 degrees behind the voltage). The magnetisation from the primary winding causes a sinusoidal domain change in a fixed direction in the material given by the primary winding's direction in the compartment: Bkvp=Kvp-sin (o3-t) 1) Where Bkvp is the magnetisation in the direction Vp, k is a constant factor proportional to the primary voltage Vp and t is time. It is now not possible to activate the secondary winding without a control current being impressed from outside in the control winding or in the secondary winding, which rotates the magnetisation from the primary winding so that the field also passes through the secondary winding. As long as the magnetisation B has a direction which is perpendicular to the secondary winding, no flux will be linked by the secondary winding. The length of the arrow illustrates the

magnetisation level B or the field strength and the direction of the arrow the direction of alignment of the domains.

In fig. 6d a control field Bkdc is introduced by activating the control winding and exciting it with DC. The control field is added to the primary field Bkvp, establishing a magnetisation Bkr as illustrated. Since a constant field is added to a sinusoidal field, the sum will change sinusoidally in direction and sinusoidally in field strength. The simplyfied diagram 6d illustrates that we obtain a change in domain alignment direction that becomes a product of two sinus functions. Both direction and field strength for the resulting field are changed sinusoidally.

The induced voltage Vs in the secondary winding will be given by two effects. The fact that the domains change direction will give an induction and the fact that the domains change in size will give an additional induction.

The directional dependence is given by Bkr = Bkvp + Bkdc 2) Where Bkr is the sum of the magnetisation from the primary side Bkvp and the magnetisation Bkdc from the control current.

The fact that the domains change in size will give an additional induction.

The field strength is given by 1), and the rotation by 2) so the combined effect will be the product of these two domain changes: Bks = Bkr. Bkvp 3) Simplified to Bkp = Kvp2 sin2 (w t) 4) Disregarding constant term Vs=K2cos (2Wt) 5) This demonstrates a frequency doubling in the secundary voltage.

This effect of the domain rotation forced on the linear domain changes from the primary current caused by the DC control current will vary by the size of the current and thus the induced voltage.

In order to be able to implement a realistic solution for a variable power transformer, the problem arises that the control winding on the primary side is transformatively connected to the primary winding and will be under voltage from the primary side, thereby making it very difficult to regulate without extensive filtering.

US patent 4,210, 859 also discloses a transformer connection (fig. 18) where windings with right-angled axes are interconnected in series two by two. The publication states that the core's utilisation can be increased by using such a connection. This is not correct, however, since the magnetic fields for the windings are summed vectorially and the described effect will not be achieved.

US patent 4,210, 859 also describes (fig. 20) a variable delay between the input and output voltage in a case where both the control windings carry current and are interconnected in series. Phase distortion is involved here since the fields through the primary and the secondary winding are shifted via the domain directions. With the control windings connected in this manner, the device will not work for a power transformer used as a phase inverter, since the connection from the primary winding will influence the control current to such an extent that in principle the same connection as mentioned earlier (fig. 18) will be obtained.

In general, the problem with the prior art as illustrated by US patent 4,210, 859 is that it does not present a complete picture of how the manipulation of the domains with a DC control current affect the magnetisation in relation to the connection between two orthogonal windings. The inventors have perfomed a thorough research in this field and have managed to map the phenomena which take place in a magnetisable material when it is excited by two orthogonal fields. Further the results of this research are used to provide a device that will work satisfactorily.

In order to overcome the above mentioned drawbacks in the prior art the invention has the following features.

According to the invention the magnetisation is controlled by means of a pulsed DC or pulsed AC control current in a secondary control winding orthogonal to the primary control winding. By controlling the magnetisation stepwise with increased voltage from the primary winding with an AC control current in the control winding as illustrated in fig. 6e, the direction of the domains will be kept constant at, e. g. , 30 degrees and only the field strength of the magnetisation will be changed in order to avoid a change in both strength and direction simultaneously.

For the magnetic circuit, according to the invention this will be achieved by means of an accurate dosing of the control current in relation to the primary winding's magnetisation current and ampere-turn balance with the secondary winding. In an ordinary transformer as illustrated in fig. 6g, the magnetisation current established by the primary winding will be given by the flux required to generate a counterinduced voltage Ep according to Faraday's law. <BR> <BR> <P>Ip-TP_EP 6)<BR> Rp Ep: Voltage induced in the primary winding Vp: Forced voltage Rp: Primary winding's resistance Ip : Primary current Ip=Ife+Im 7) Disregarding leakage fields, the common flux for primary and secondary winding is given by m=NpIm Rcore Np: Primary winding's number of turns Im: The magnetisation current Rcore: The reluctance in the core With an open secondary circuit there is only magnetisation current in the primary winding. According to Lenz's law emf = electromotive voltage induced in the secondary winding will be in such a direction that it will

counteract the flux change that created it. When the secondary winding is connected to a load (the switch S in fig. 6g is closed), the secondary winding's own magnetomotive force Fs= mmf or flux Os will immediately (in the transient sequence) be established, which will be in the opposite direction to mmf from the primary winding Fp. This is illustrated in fig. 6g.

In a moment the flux in the core will decrease to #m = Np-im-Ns.is 8) Rcore where is is the secondary current and Ns the number of turns in the secondary winding. The flux reduction will lead to a reduction in the induced voltage in the primary winding and thereby according to equation 6) an increase in the primary current. This increased primary current, which is the load current component in the primary current, adds its mmf vectorially to the magnetisation component Np*im, causing an increase in the primary flux <BR> <BR> Dm=Np im+Np ip, load-Ns is<BR> Rcore The primary current increases until Np Ip, load = Ns-Is and then ct) m and Ep are on the same level as they were before the switch was closed. In stationary operation we will have a current in the primary winding Ip = If e + Im+ Ip, load 10) When the switch opens the same sequence will be repeated in the opposite direction. It is interesting to note that at the moment when the switch is closed we actually have a secondary mmf, which establishes a magnetisation that is orthogonal to the original magnetisation from the primary winding because the secondary winding is orthogonal to the first. The primary winding replies with a corresponding magnetisation mmf oppositely directed to the secondary winding's mmf and orthogonal to the original magnetisation. Thus we see that Lenz's law maintains a balance in the flux, with every load change on the secondary side being met by a corresponding change on the primary side, thus achieving a balance, with the result that in a stationary state we will only have the magnetisation flux flowing in the core that is the cause of the transformer effect. This description applies for an ordinary transformer with primary and secondary winding in the same winding compartment.

According to the invention a magnetisation current is established in the control winding that conforms to the magnetisation current from the primary winding in amplitude in order to enable a transformative connection to be established between the primary and secondary winding that does not produce undesirable frequencies in the secondary voltage. Without this magnetisation it is not possible to activate transformative connection to the secondary winding. There will be some degree of connection on account of the winding's extension in the compartment, which will provide an induced component and also a second induced component due to nonlinearities in the material, but this connection will not be capable of providing the desired transformative effect.

We have now established a magnetisation in the core that provides connection to the secondary side by means of the current in the control winding. We shall therefore have two magnetisation currents, which are orthogonal and are summed in such a manner that the domain direction is changed linearly in a direction that is at an angle to the secondary winding and where induced voltage in the secondary winding will be dependent on the size of this angle.

Since the sum of the magnetisation currents is the cause of the transformer effect, we want to keep the controlled part of the magnetisation current in the secondary circuit unaffected by load changes in the secondary circuit, i. e. the current in the control winding is kept constant during a load change. By introducing a suitable inductance in the control winding, e. g. by means of the prior art from PCT/NO01/00217, the current in the control winding will be perceived as constant during domain changes caused by load changes in the secondary circuit this is because an inductance will"smooth"the changes in the current. We should be aware that now that the transformer effect is present, the control winding will also be under induction from the primary voltage Vp. The control winding is also directly transformatively connected to the secondary winding and a control voltage in the control winding will be transformed to the secondary winding. At the same time current in the secondary winding will now influence the domain distortion and the phase ratio between primary and secondary winding. In order to remedy this situation, all currents in the system must be monitored and the control winding must be excited so as to compensate for domain changes established by the secondary winding. In order to prevent power passing from the control

circuit to the secondary circuit and these influencing each other, as mentioned earlier an inductance is introduced in the control circuit that causes an approximately constant current in the control winding and gives a sufficient drop in voltage between the control winding and the secondary winding. The transformed voltage in the secondary winding from the primary side and the transformed voltage in the secondary winding from the control winding will be in phase or in antiphase, since we have basically used a control voltage that should be in phase with the primary voltage in order to obtain a directionally constant domain change. It is also important to be aware that the core is reset at every zero passage in the voltages. Thus by removing the control current the magnetisation angle between the windings will decrease due to the fact that the secondary current decreases and after a few periods we are back to minimal connection.

We can conclude with the following: 1) The control voltage in the method according to the invention is in phase or antiphase with the primary voltage in order to achieve distortion-free transformative connection.

2) Through a slow change in the amplitude of the control voltage, the direction of the domain change or the magnetisation angle between primary and secondary winding can be changed and thereby the voltage transfer can be controlled.

3) Through introduction of an inductance in the control circuit it will be possible to suppress the effect of the direct transformative connection between secondary and control winding.

4) The secondary winding will act as a control winding by electromotive force (mmf) therefrom being added to electromotive force (mmf) from the control winding and influencing the magnetisation angle between the primary and the secondary winding.

5) Basically, it is not possible to isolate this effect from the secondary winding and we shall obtain a variable phase angle rotation between primary and secondary according to the load conditions.

However, we can compensate for this by using a phase

compensation device as described in PCT/NO01/00217 to compensate for the phase angle rotation.

6) Since the primary winding will immediately response to any load change from the secondary side, according to Lenz's law we shall achieve the desired regulating transformer effect.

In a preferred embodiment, the transformer according to the invention comprises only one control winding located in the winding compartment together with the secondary winding. In principle, a control winding in the primary winding compartment is not necessary since the primary winding will rotate the domains in its'direction and also rotate any domains established from a current in the secondary winding to the same direction. In order to obtain transformative connection between the orthogonal windings, the domains must be rotated as mentioned above in order to efficiently produce a magnetisation that is in a favourable direction for transformative connection between the primary and the secondary winding. The best that can be achieved is a rotation of 45 degrees for the domains. (From a different point of view, we"twist"the secondary winding relative to the primary winding in such a manner that some of the field from the primary winding passes through the secondary winding.) In order to achieve transformer effect without distortion of the primary voltage, according to the invention an (AC) alternating voltage is used on the control winding, which as previously mentioned is located in the same winding compartment as the secondary winding. When current begins to flow in the control winding, this current will reinforce the connection with the primary side by the domains being helped in the right direction by the field from the secondary current and the field from the control current.

In a preferred embodiment, the control voltage in the transformer according to the invention will be in phase with or phase shifted 180 degrees relative to the voltage on the primary side in order to obtain a distortion-free transformation. The current in the control winding can be regulated by a system that monitors the primary and the secondary current/voltage as well as the control current, thus enabling the connection and the electrical angle between the windings to be controlled by means of the alignment of the domains. As mentioned before, the values of current and voltage in the primary, secondary and control winding will give a clear indication of the

state of the domains (rotation and magnetisation) and thus these parameters together with reference values can be used for controlling the transformer's operation and adapt it to different operation conditions.

The transformer according to the invention may also advantageously be employed as a controlled rectifier or frequency converter. In order to achieve such a controlled rectifier effect from this transformer, two methods may be employed. These will be described in detail with reference to the drawings.

The first method comprises: - connecting the primary winding of a first transformer to a power supply, - connecting a central point of the secondary winding of said first transformer to a load, - connecting the ends of said first secondary winding to a first diode rectifier topology, - supplying an AC voltage to the first control winding in the first transformer, - connecting the primary winding of a second transformer to a power supply, - connecting a central point of the secondary winding of said second transformer in parallel with the central point of the first transformer to said load, - connecting the ends of the secondary winding of said second transformer to a second diode rectifier topology, - supplying an AC voltage to the second control winding in the second transformer, - providing thus a frequency converter for motor control. A rectification is provided accorsding to this method which comprises the following steps: 1) the first control winding of the first transformer is activated and during the activation a transformer effect occurs between the primary winding and the secondary winding of the first transformer, the voltage from the secondary winding of the first transformer is rectified by diodes D 1 and D2 and the resulting voltage applies over the load. the primary winding of the second transformer is in off state as the control winding of the second transformer is not activated providing a high impedance in the secondary winding of the second transformer is in paralell to the load, during the period in which the first control winding is activated a voltage on the primary of the first transformer is rectified and appears on the load as a positive voltage, 2) the control winding of the first transformer is deactivated and during the deactivation the secondary winding of the first transformer is in a state of high

impedance, the control winding of the second transformer is activated and during the activation a transformer effect occurs between the primary and the secyundary windings of the transformer, - the voltage from the secundary winding of the second transformer is rectified by the second diode configuration and the resulting voltage Vdc applies over the load U1, - during the period in which the control winding of the second transformer is activated a voltage on the primary winding of this transformer is rectified and appears on the load as a negative voltage 3) by controlling the activation of the control windings to control the length of the negative and the positive rectifier period, a variable frequency control from 0 to 50 Hz will be obtained.

When domains change size and direction, the body's magnetisation will be altered accordingly, inducing voltages in windings where the domains are under an angle that is not orthogonal to the windings.

The transformative connection between the primary and the secondary side will be as for an ordinary transformer as long as the transformation occurs in the linear region of the magnetisation curve and as long as the directional dependence of the permeability in the plate is approximately symmetrical and the control current is in phase with the primary voltage and of such a strength that the direction of the domains is not changed during the primary voltage sequence.

With regard to the prior art from PCT/NO01/00217, which is hereby incorporated as a reference in its entirety, the invention relates to a new device, since the primary and the secondary windings do not have parallel, but right-angled winding axes, and a control of the domain state is included.

The invention will now be described in detail with reference to the drawings.

Figures 1 and 2 illustrate the basic principle of the invention and a first embodiment thereof.

Figure 3 illustrates the areas of the different magnetic fluxes involved in the device according to the invention.

Figure 4 illustrates a first equivalent circuit for the device according to the

invention.

Figures 5 and 6 illustrate magnetisation curves and domains for the magnetic material in the device according to the invention.

Figure 7 illustrates flux densities for the main and the control winding.

Figure 8 illustrates a second embodiment of the invention.

Figure 9 illustrates the same second embodiment of the invention.

Figures 10 and 11 illustrate the second embodiment in section.

Figures 12-15 illustrate various embodiments of the magnetic field connectors in the said second embodiment of the invention.

Figures 16-29 illustrate various embodiments of the tubular bodies in the second embodiment of the invention.

Figures 30-35 illustrate different aspects of magnetic field connectors for use in the second embodiment of the invention.

Figure 36 illustrates an assembled device according to the second embodiment of the invention.

Figures 37 and 38 illustrate a third embodiment of the invention.

Figures 39-41 illustrate special embodiments of magnetic field connectors for use in the third embodiment of the invention.

Figure 42 illustrates the third embodiment of the invention adapted for use as a transformer.

Figures 43 and 44 illustrate the fourth embodiment of the invention adapted to a powder-based magnetic material, and thereby without magnetic field connectors.

Figures 44 and 45 illustrate a section along lines VI-VI and V-V in figure 42.

Figures 46 and 47 illustrate a core adapted to a powder-based magnetic material, and thereby without magnetic field connectors.

Figure 48 illustrates a circuit for controlled rectification.

Figures 49 and 50 illustrate an alternative circuit for controlled rectification.

The invention will now be explained in principle in connection with Figs. la and lb.

In the entire description the arrows associated with magnetic field and flux will substantially indicate the directions thereof within the magnetic material.

The arrows are depicted on the outside for the sake of clarity.

Figure la illustrates a device comprising a body 1 of a magnetisable material that forms a closed magnetic circuit. This magnetisable body or core 1 may be annular in form or of another suitable shape. Around the body 1 is wound a first main winding 2, where the direction of the magnetic field H1 (corresponding to the direction of the flux density B 1) that will be produced when the main winding 2 is excited will conform to the magnetic circuit. The main winding 2 resembles a winding in an ordinary transformer. In an embodiment the device comprises a second main winding 3, which is wound round the magnetisable body 1 in the same way as the main winding 2 and which will thereby provide a magnetic field extending substantially along the body 1 (i. e. parallel to H1, B1). Finally, the device comprises a third main winding 4, which in a preferred embodiment of the invention extends internally along the magnetic body 1. The magnetic field H2 (and thereby the flux density B2) that is created when the third main winding 4 is excited, will have a direction that is at right angles to the direction of the fields in the first and the second main winding (direction of H1, B 1). According to a preferred embodiment of the invention the third main winding 4 constitutes a primary winding, the first main winding 2 the secondary winding and the second main winding 3 the control winding. In the topologies that are considered to be preferred in the present description, however, the turns in the main winding follow the field direction from the control field and the turns in the control winding follow the field direction of the working field.

Figures lb-lg illustrate the definition of the axes and the direction of the various windings and the magnetic body. As far as the windings are concerned, we shall call the axis the normal of the surface defined by each turn. The secondary winding 2 will have an axis A2, the control winding 3 an axis A3 and the primary winding 4 an axis A4.

With regard to the magnetisable body 1, the longitudinal direction will vary according to the shape. If the body is elongated, the longitudinal direction Al will coincide with the body's longitudinal axis. If the magnetic body is square as illustrated in figure la, it will be possible to define a longitudinal direction Al for each leg of the square. Where the body is tubular, the longitudinal direction Al will be the tube's axis, and for an annular body the longitudinal direction Al will follow the circumference of the ring.

The invention is based on the principle of aligning the domains in the core in the magnetisable body 1 in relation to a first magnetic field H2 by changing a second magnetic field H1 that is at right angles to the first. Thus the field H2

may, for example, be defined as the working field and control the body's 1 domain direction (and thereby the behaviour of the working field H2) by means of the field H1 (hereinafter called control field HI). This will now be explained in greater detail.

The magnetisation in the core is directionally determined by the sources of the field that influence the domains in the material. Normally the winding compartment, i. e. the part of the core that contains the windings, is common to primary and secondary winding, with the result that domain direction and magnetisation are also common. In a preferred embodiment of the invention the winding compartments are orthogonal with the result that the fields from the two windings are orthogonal and consequently there is no magnetic connection between the windings as long as no current is flowing in the control winding and the secondary winding.

As already mentioned, in figs. la and 2a winding 4 is the primary winding and winding 2 the secondary winding while winding 3 is the control winding.

Fig. 4 shows Al as the flux area for secondary winding 2 and control winding 3 and this area may be called the area for the internal winding compartment iws, and A2 the flux area for the primary winding 4, or the area of the external winding compartment ews. Depending on the kind of conversion and connection required, it will be possible to give the areas equal or unequal dimensions.

Fig. 4 is a diagram illustrating the transformer according to the invention where the windings are located with parallel and right-angled axes, and where the magnetisation direction is also represented.

In order to achieve a transformative connection between the two orthogonal windings, the domains and thereby the magnetisation must be aligned in such a manner that the angle between the domains and the windings that have to be influenced is different from 90 degrees. The best that can be achieved with connection between two orthogonal windings is to align the magnetisation in the body 1 by means of a control winding to 45 degrees.

This means that with an equal number of turns on the primary and the secondary winding and the same flux area, a maximum of approximately 70% of the voltage can be transformed since sinus of 45 degrees is 0.707 and is the part of the flux area a winding rotated at 45 degrees relative to a source winding will cover.

The essence of what is occurring is illustrated in figs. 5 and 6.

Fig. 5 illustrates the magnetisation curves for the entire material of the magnetisable body 1 and the domain change under the influence of the H1 field from the secondary winding 2.

Fig. 6 illustrates the magnetisation curves for the entire material of the magnetisable body 1 and the domain change under the influence of the H2 field in the direction of the winding 4.

Figs. 7a and 7b illustrate the flux densities B1 (where the field H1 is established by the secondary winding) and B2 (corresponding to the primary current). The ellipse illustrates the saturation limit for the B fields, i. e. when the B field reaches the limit, this will cause the material of the magnetisable body 1 to reach saturation. The design of the ellipse's axes will be given by the field length and the permeability of the two fields B1 (H1) and B2 (H2) in the core material of the magnetisable body 1.

By letting the axes in figure 7 express the MMK distribution or the H-field distribution, a picture can be seen of the magnetomotive force from the two currents I1 and I2. The operative range of the transformer will be within the saturation limit and it is particularly important to take account of this when designing the transformer for the magnetisation fields in a connection between two orthogonal windings.

Figure 8 is a schematic illustration of a second embodiment of the invention.

Fig. 9 illustrates the same embodiment of a magnetically influenced connector provided in a preferred embodiment of the transformer according to the invention, where fig. 9a illustrates the assembled connector and fig. 9b is an end view of the connector.

Fig. 10 illustrates a section along line II in figure 9b.

As illustrated, for example, in figure 10, the magnetisable body 1 is co mposed inter alia of two parallel tubes 6 and 7 made of a magnetisable material. An electrically insulated conductor 8 (figs. 9a, 10) is passed continuously in a path through the first tube 6 and the second tube 7 N number of times, where N = 1,... r, forming the primary main winding 2, with the conductor 8 extending in the opposite direction through the two tubes 6 and 7, as is clearly illustrated in fig. 10. Even though the conductor 8

is only shown extending through the first tube 6 and the second tube 7 twice, it should be self-explanatory that it is possible for the conductor 8 to extend through the respective tubes either only once or possibly several times (as indicated by the fact that the winding number N can vary from 0 to r), thereby creating a magnetic field H1 in the parallel tubes 6 and 7 when the conductor is excited. A combined control and secondary winding 4, 4', composed of the conductor 9, is wound round the first tube and the second tube (6 and 7 respectively), in such a manner that the direction of the field H2 (B2) that is created on the said tubes when the winding 4 is excited will be oppositely directed, as indicated by the arrows for the field B2 (H2) in figure 8. Magnetic field connectors 10,11 are mounted at the ends of the respective tubes 6,7 in order to interconnect the tubes fieldwise in a loop.

The conductor 8 will be able to convey a load current Il (fig. 9a). The tubes' 6,7 length and diameter will be determined on the basis of the power and voltage that have to be connected. The number of turns N1 on the main winding 2 will be determined by the reverse blocking ability for voltage and the cross-sectional area for the magnitude of the working flux cl) 2. The number of turns N2 on the control winding 4 is determined by the conversion ratio required for the special transformer.

Another possibility is to arrange the winding 4 as primary winding and the winding 2 as control and secondary winding.

Figure 11 illustrates an embodiment where the primary and the secondary main windings have been interchanged. In reality, the solution in fig. 11 differs from that illustrated in figs. 9a and 10 only by the fact that instead of a single insulated conductor 8, which is passed through the tubes 6 and 7, two separate oppositely directed conductors, so-called secondary conductors 8 and control conductors 8'are employed, in order thereby to achieve a voltage converter function in the magnetically influenced device according to the invention. The design basically resembles that illustrated in figs. 8,9 and 10. The magnetisable body 1 comprises two parallel tubes 6 and 7. An electrically insulated secondary conductor 8 is passed continuously in a path through the first tube 6 and the second tube 7 N1 number of times, where N1 = 1,... r, with the conductor 8 extending in the opposite direction through the two tubes 6 and 7. An electrically insulated control conductor 8'is passed continuously in a path through the first tube 6 and the second tube 7 Nl' number of times, where N1'= 1,... r, with the conductor 8'extending in the

opposite direction relative to the conductor 8 through the two tubes 6 and 7.

At least one primary winding 4 and 4'is wound round the first tube 6 and the second tube 7 respectively, with the result that the field direction created on the said tubes is oppositely directed. In the same way as for the embodiment according to figs. 8,9 and 10, the magnetic field connectors 10,11 are mounted at the end of the respective tubes 6,7 in order to interconnect the tubes 6 and 7 fieldwise in a loop, thereby forming the magnetisable body 1.

Even though for. the sake of simplicity in the drawings the conductor 8 and the conductor 8'are illustrated with only one pass through the tubes 6 and 7, it will be immediately apparent that both the conductor 8 and the conductor 8'will be able to be passed through the tubes 6 and 7 N1 and N1'number of times respectively. The tubes'6 and 7 length and diameter will be determined on the basis of the power and voltage that have to be converted. For a transformer with a conversion ratio (N1 : N1') equal to 10: 1, in practice ten conductors will be used as conductors 8 and only one conductor 4.

An embodiment of a magnetic field connector 10 and/or 11 is illustrated in figure 12. A magnetic field connector 10,11 is illustrated composed of magnetically conducting material, wherein two preferably circular apertures <BR> <BR> 12 for the conductor 8 in the winding 2 (see, e. g. , fig. 10) are machined out of the magnetic material in the connectors 10, 11. Furthermore, a gap 13 is provided which interrupts the magnetic field path of the conductor 8. End surface 14 is the connecting surface for the magnetic field H2 from the winding 4 consisting of conductor 9 and 9' (fig. 10).

Fig. 13 illustrates a thin insulating film 15 which will be placed between the end surface of tubes 6 and 7 and the magnetic field connector 10,11 in a preferred embodiment of the invention.

Figures 14 and 15 illustrate other alternative embodiments of the magnetic field connectors 10,11.

Figures 16-29 illustrate various embodiments of a core 16, which in the embodiment illustrated in figures 9,10 and 11 forms the main part of the tubes 6 and 7, which preferably together with the magnetic field connectors 10 and 11 form the magnetisable body 1.

Fig. 16 illustrates a cylindrical core part 16, which is divided lengthwise as illustrated and where one or more layers 17 of insulating material are placed between the two core halves 16,'16".

Fig. 17 illustrates a rectangular core part 16 and fig. 18 illustrates an embodiment of this core part 16 where it is divided in two with partial sections in the lateral surface. In the embodiment illustrated in figure 18 one or more layers of insulating material 17 are placed between the core halves 16,16'. A further variant is illustrated in figure 22 where the partial section is placed in each corner.

Figs. 20,21 and 22 illustrate a rectangular shape. Figures 23,24 and 25 illustrate the same for a triangular shape. Figs. 26 and 27 illustrate an oval variant, and finally figures 28 and 29 illustrate a hexagonal shape. In figure 28 the hexagonal shape is composed of 6 equal surfaces 18 and in fig. 27 the hexagon consists of two parts 16'and 16". Reference numeral 17 refers to a thin insulating film.

Figures 30 and 31 illustrate a magnetic field connector 10,11 that can be used as a control field connector between the rectangular and square main cores 16 (illustrated in figures 10-11 and 20-22 respectively). This magnetic field connector comprises three parts 10', 10"and 19.

Figure 31 illustrates an embodiment of a core part or main core 16 where the end surface 14 or the connecting surface for the control flux is at right angles to the axis of the core part 16.

Figure 32 illustrates a second embodiment of the core part 16 where the connecting surface 14 for the control flux is at an angle a relative to the axis of the core part 16.

Figures 33-39 illustrate various designs of the magnetic field connector 10, 11, which are based on the fact that the connecting surfaces 14'of the magnetic field connector 10,11 are at the same angle as the end surfaces 14 to the core part 16.

Fig. 33 illustrates a magnetic field connector 10, 11 in which different hole shapes 12 are indicated for the main winding 2 based on the shape of the core part 16 (round, triangular, etc.).

In fig. 34 the magnetic connector 10,11 is flat. It is adapted for use with core parts 16 with right-angled end surfaces 14.

In fig. 35 an angle a'is indicated to the magnetic field connector 10,11, which is adapted to the angle a to the core part 16 (figure 32) with the result that the end surface 14 and the connecting surface 14'coincide.

In fig. 36a an embodiment of the invention is illustrated with an assembly of magnetic field connectors 10,11 and core parts 16. Figure 36b illustrates the same embodiment viewed from the side.

Even though only a few combinations of magnetic field connectors and core parts are described in order to illustrate the invention, it will be obvious to a person skilled in the art that other combinations are entirely possible and will therefore fall within the scope of the invention.

It will also be possible to switch the positions of the primary winding and the secondary and control windings. However, the control winding will preferably follow the same winding compartment as the secondary winding.

Figures 37 and 38 are a sectional illustration and a view respectively illustrating a third embodiment of a magnetically influenced voltage connector device. The device comprises (see figure 37b) a magnetisable body 1 comprising an external tube 20 and an internal tube 21 (or core parts 16, 16') that are concentric and made of a magnetisable material with a gap 22 between the external tube's 20 inner wall and the internal tube's 21 outer wall. Magnetic field connectors 10,11 between the tubes 20 and 21 are mounted at respective ends thereof (fig. 37a). A compartmentr 23 (fig. 37a) is placed in the gap 22 thus keeping the tubes 20,21 concentric. A primary winding 4 composed of conductors 9 is wound round the internal tube 21 and is located in the said gap 22. The winding axis A2 for the primary winding 4 therefore coincides with the axis Al of the tubes 20 and 21. An electrical current-carrying or secondary winding 2 composed of the current conductor 8 is passed through the internal tube 21 along the outside of the external tube 20 N1 number of times, where N1 = 1,... r. With the primary winding 4 cooperating with the secondary winding 2 or the said current-carrying conductor 8, an easily constructed, but efficient magnetically influenced transformer or switch is obtained. An electrical current-carrying or control winding 3 composed of the current conductor 8'is passed through the

internal tube 21 and along the outside of the external tube 20 N1 number of times, where N1 = 1,..., r. This embodiment of the device can also be modified so that the tubes 20,21 do not have a round cross section but a cross section that is square, rectangular, triangular, etc. We must define « winding compartment » better. It is not exactly a cavity in the core, since the windings are wound round the walls of the core.

It is also possible to wind the primary main winding round the internal tube 21, in which case the axis A2 for the main winding will coincide with the axis Al of the tubes while the control and the secondary winding are wound round the tubes on the inside of 21 and the outside of 20.

Figs. 39-41 illustrate different embodiments of the magnetic field connector 10,11, which are specially adapted for the last-mentioned embodiment of the invention, i. e. that described in connection with figures 37 and 38.

Figure 39a is a sectional view and figure 39b a view from above of a magnetic field connector 10,11 with connecting surfaces 14'at an angle relative to the axis of the tubes 20,21 (the core parts 16) and naturally the internal 21 and external 20 tubes will also be at the same angle to the connecting surfaces 14.

Figs. 40 and 41 illustrate other variants of the magnetic field connector 10, 11 where the connecting surfaces 14'of the control field H2 (B2) are at right angles to the main axis of the core parts 16 (tubes 20,21).

Figure 40 illustrates a hollow semi-toroidal magnetic field connector 10,11 with a hollow, semicircular cross section, while figure 39 illustrates a toroidal magnetic field connector with a rectangular cross section.

Figure 42 illustrates the third embodiment of the invention adapted for use as a transformer.

Figures 43 and 44 illustrate an embodiment of the invention adapted to a powder-based magnetic material, and thereby without magnetic field connectors.

Figures 44 and 45 illustrate a section along lines VI-VI and V-V in figure 42.

Figures 46 and 47 illustrate a core adapted to a powder-based magnetic material, and thereby without magnetic field connectors.

Figure 48 shows an embodiment of the method according to the invention.

This method comprises: - connecting the primary winding (T3) of a first transformer to a power supply, - connecting a central point (c4) of the secondary winding (T2) of said first transformer to a load (motor, R1, Ll), - connecting the ends of said first secondary winding (c5, c3) to a first diode rectifier topology (D1, D2 respectively), - supplying an AC voltage to the first control winding (T1) in the first transformer, - connecting the primary winding (T4) of a second transformer to a power supply, - connecting a central point (c4') of the secondary winding (T6) of said second transformer in parallel with the central point (c4) of the first transformer to said load (motor), - connecting the ends (c5', c3') of the secondary winding (T6) of said second transformer to a second diode rectifier topology (D3, D4 respectively), - supplying an AC voltage to the second control winding (T5) in the second transformer, - providing thus a frequency converter for motor control. A rectification is provided accorsding to this method which comprises the following steps: 1) the first control winding (T1) of the first transformer is activated and during the activation a transformer effect occurs between the primary winding and the secondary winding of the first transformer (T3, T2), the voltage from the secondary winding of the first transformer (T2) is rectified by diodes D1 and D2 and the resulting voltage (Vdc) applies over the load (U1). the primary winding of the second transformer (T4) is in off state as the control winding of the second transformer (T5) is not activated providing a high impedance in the secondary winding of the second transformer (T6) is in paralell to the load (Ul). during the period in which the first control winding (T1) is activated a voltage on the primary (T3) of the first transformer is rectified and appears on the load (Ul) as a positive voltage, 2) the control winding of the first transformer (T1) is deactivated and during the deactivation the secondary winding of the first transformer (T2) is in a state of high impedance, the control winding of the second transformer (T5) is activated and during the activation a transformer effect occurs between the primary and the secyundary windings of the transformer (T4 and T6 respectively),

- the voltage from the secundary winding of the second transformer (T6) is rectified by the second diode configuration (D3, D4) and the resulting voltage Vdc applies over the load U1, - during the period in which the control winding of the second transformer (T5) is activated a voltage on the primary winding of this transformer (T4) is rectified and appears on the load (U1) as a negative voltage 3) by controlling the activation of the control windings (T1 and T5) to control the length of the negative and the positive rectifier period, a variable frequency control from 0 to 50 Hz will be obtained.

Tl and T5 are excited by a DC signal.

Figures 49 and 50 illustrate another method for rectification by means of a first and a second transformer device according to the invention, comprising (fig. 49,50) : - connecting the primary winding (T3) of the first transformer to a power supply, - connecting the secondary winding (T2) of said first transformer to a load (motor) - supplying an AC voltage to the control winding (T1) in the first transformer, - connecting the primary winding (T4) of a second transformer to a power supply, - connecting the secondary winding (T6) of said second transformer in anti-parallel to said load load (motor), - supplying an AC voltage to the second control winding (T5) in the second transformer, wherein - Vp which is the AC voltage common to the two primaries (T3, T4) resets the cores S 1 (T3) and S2 (T4) when there is no transformer connection to the secondary side because T1 and T5 are deactivated, - during the first part of the positive phase of Vp the control winding of the first tranformer (Tl) is activated and transformative connection to the secundary winding of the first transformer (T2, voltage Vsl) is obtained, - after the zero passage of the negative phase the control winding of the second transformer (T5) is activated (voltage Vk2) and the voltage Vs2 (voltage on the secondary winding of the second transformer T6) is connected to the circuit, the rectification is obtained by: - the connection of the primary winding being made so that on T3 the terminal cl is connected to LI and terminal c2 is connected to L2, the primary connection to T4 is opposite ; terminal c'1 is connected to L2 and terminal c'2 to LI, Ll and L2 represent the terminals of an AC power source, - the connection of the secondary windings (T2 and T6) to the load is made so that the two secondaries are paralell connected to the load,

- a pulsed control voltage Vkl is applied in phase and opposite with Vp on T3 (tO in figure 50), Vsl is induced by this action and appears on both the load and on T6, T6 is in high impedance mode and the current is applied on the load, - at the next zero crossing (tl) on the primary voltage Vp Vkl is removed, T2 returns to high impedance, - at the next zero crossing (2) Vk2 is applied and again a voltage Vs2 appears on the load and on T2.

Figure 50 is a time vs voltage diagram that shows how the method is implemented by controlling the voltage in the load by means of the voltages in the two control windings.