Tesla Transformer

Abstract

A Tesla transformer 70 comprises an inner magnetic core 32, an outer magnetic core 34, a primary winding 36 and a secondary winding 78. The secondary winding comprises a parallel connection of two or more windings 78a, 78b and may be encased in dielectric material 39 to form a coaxial structure. A first secondary winding portion may taper and slope in a first direction, away from the outer magnetic core and towards an electrical stress ring (37, figure 3). A second secondary winding portion may taper and slope in a second direction, away from the stress ring and towards the inner magnetic core. The stress ring may be located at a mid-point between the inner and outer magnetic cores. The stress ring may electrically connect the first and second portions and act as a turn of the secondary winding. There may be a plurality of electrical stress rings.

Description

Field of the invention This invention relates to Tesla transformers. Background Tesla transformer designs are sought that enable a relatively small transformer to provide a relatively high power output. This may, for example, enable reduced size Tesla transformers to be developed (without reducing power output) and / or higher power Tesla transformers to be developed (without increasing device size). Such transformers may be referred to as compact Tesla transformers. Summary of the invention In an aspect of the present invention, there is provided a Tesla transformer comprising: an inner magnetic core; an outer magnetic core; a primary winding; and a secondary winding. The secondary winding comprises a parallel connection of two or more windings. The parallel connection may be provided in order to provide a relatively low unit electrical resistance path (i.e. a lower unit electrical resistance path than a single winding). The secondary winding may be encased in a dielectric material to form a coaxial structure. ' V The Tesla transformer may further comprise one or more inputs configured to enable an input signal from a driver section to be discharged through the primary winding. Alternatively, the Tesla transformer may further comprise a Tesla driver section for providing an input signal to be discharged through the primary winding. In some example embodiments, the Tesla transformer further comprises an electrical stress ring, wherein the secondary winding comprises: a first secondary winding portion (that is tapered and slopes, in a first direction, away from the outer magnetic core and towards the electrical stress ring); and a second secondary winding portion (that is tapered and slopes, in a second direction different to the first direction, away from the electrical stress ring and towards the inner magnetic core), wherein one of said first and second secondary winding portions comprises said parallel connection of two or more windings. The electrical stress ring may, for example, be positioned at a mid-point between voltages at the inner and outer magnetic cores. The secondary winding may be encased in a dielectric material to form a coaxial structure and wherein the electrical stress ring may be positioned at a mid-point between voltages at inner and outer conductors of the coaxial structure. The electrical stress ring may comprises a radiussed edge, wherein the first and second secondary winding portions are electrically connected via the radiussed edge. The electrical stress ring may act as a turn of the secondary winding. In some example embodiments, the Tesla transformer further comprises a second electrical stress ring, wherein the secondary winding comprises a third secondary winding portion, wherein the second secondary winding portion slopes towards the second electrical stress ring and the third secondary winding portion slopes, in the first direction, away from the second electrical stress ring and towards the inner magnetic core, wherein one or more of said first, second and third secondary winding portions comprising said parallel connection of two or more windings. Moreover, the Tesla transformer may further comprise a third electrical stress ring, wherein the secondary winding comprises a fourth secondary winding portion, wherein the third secondary winding portion slopes towards the third electrical stress ring and the fourth secondary winding portion slopes, in the second direction, away ■ from the third electrical stress ring and towards the inner magnetic core, wherein one or more of said first, second, third and fourth secondary winding portions comprising said parallel connection of two or more windings. In some example embodiments, the Tesla transformer comprises a plurality of electrical stress rings, wherein the secondary winding comprising a plurality of secondary winding portions. Brief Description of the Drawings There follows, by way of example only, a detailed description of specific embodiments of the invention with reference to the accompanying drawings in which: Figure 1 is a system in accordance with an example embodiment; Figure 2 is a cross-section of an example Tesla transformer; Figure 3 is a cross-section showing an aspect of Tesla transformer design in accordance with an example embodiment; Figure 4 is a plot showing a voltage distribution in accordance with an example embodiment; Figures 5 to 10 are cross-sections showing portions of Tesla transformers in accordance with example embodiments; and Figure 11 is a close up view of an example implementation of a stress ring used in some example embodiments. Detailed Description Figure 1 is a system, indicated generally by the reference numeral 10, in accordance with an example embodiment. The system 10 comprises a primary coil 12 and a secondary coil 14 that together form a transformer. As described in detail below, the transformer formed of the primary coil 12 and the secondary coil 14 may be configured as a Tesla transformer. The system 10 may comprise a driver 16 and may comprise a load 18. The driver 16 enables an input signal to be discharged through windings of the primary coil 12. In response, a high voltage pulse can be generated in windings of the secondary coil 14 (based on the turns ratio between the secondary and primary windings and the coupling factor between the magnetic cores). In this way, a range of radio frequency (RF) outputs can be delivered to the load 18, if provided. As is known in the art, a high pressure gas switch (not shown in Figure 1) may be used to discharge the high voltage pulse to the load. Tesla transformers may be used, for example, as sources for a Radio Frequency Directed Energy Weapon (RFDEW). Tesla transformers in such systems can provide a range of high power radio frequency outputs and are a versatile technology. Nevertheless, it may be advantageous to provide smaller Tesla transformers (without reducing power output) and / or to provide higher power Tesla transformers (without increasing device size). Figure 2 is a cross-section of an example Tesla transformer, indicated generally by the reference numeral 20. The Tesla transformer 20 comprises an inner magnetic core 22, an outer magnetic core 24, a primary winding 26, and a tapered secondary winding 28. The two magnetic cores 22,24, the primary winding 26 and the tapered secondary winding 28 are encased in dielectric 29, thereby forming a coaxial structure. The primary winding 26 may be connected (e.g. on the left of the Tesla transformer structure 20 shown in Figure 2) to a Tesla driver (such as the driver 16 described above). Similarly, the secondary winding 28 may be connected to an external load (such as the load 18 described above) - note that the dielectric material of the Tesla transformer that surrounds the secondary winding is sometimes used as the only load. Thus, the Tesla transformer 20 may be used to provide the primary coil 12 and secondary coil 14 of the system 10 described above. Outer sections of insulators of the Tesla transformer 20 may be metallised to allow high currents to flow down the coaxial structure of the transformer. Such metallisations may be formed in strips (e.g. in the form of inner and outer cages) to allow the magnetic field to traverse around the transformer and through the magnetic cores. The primary winding 26 may consist of just a few turns of copper sheet. The tapered secondary winding 28 may be wound using thin enamelled copper wire consisting of a few thousand turns (thereby generating a turns ratio for the transformer in the order of 103). In some example embodiments, pulse capacitors of a driver circuit (e.g. the driver 16) are discharged through the primary winding 26 such that substantial high voltage pulses can be developed on the secondary winding 28 due to the turns ratio between the windings. Depending on the positioning of the primary winding 26, the high voltage may, for example, be developed on an outer case of the Tesla transformer or on an inner conductor. In use, a high voltage potential can be developed between the inner and outer parts of the coaxial structure of the Tesla transformer 20; this charges the dielectric material 29. The dielectric 29 which holds the secondary winding 28 can form the load of an RF source. Alternatively, or in addition, a separate load (such as the load 18) can be provided (e.g. adjacent to, or wrapped around, the outer case of the Tesla transformer 20). Once the load to charged, the load can be discharged using a high pressure gas switch to produce a high power RF pulse. The frequency content and energy of this pulse may vary, for example, dependent on one or more of the geometry of the Tesla transformer 20, the geometry of the load, and gas switching parameters. One mechanism for maximising the output voltage of a Tesla transformer (and hence the output power) is to maximise the number of turns erf the secondary winding 28. This could be achieved, for example, by increasing the coaxial dielectric gap between the inner magnetic core 22 and the outer magnetic core 24; however this would result in less magnetic coupling (since the cores would be further apart). Alternatively, or in addition, the secondary winding 28 could be formed from thinner wire so that more turns can fit into the same taper; however, using thinner wire would cause the losses in the secondary circuit to increase (since the DC resistance in the secondary circuit is proportional to the cross-sectional area of the copper wire used, which follows a squared relationship). A further option would be to increase the length of the Tesla transformer, but this may not be possible due to space constraints. Figure 3 is a cross-section, indicated generally by the reference numeral 30, showing an aspect of Tesla transformer design in accordance with an example embodiment. The Tesla transformer 30 comprises an inner magnetic core 32 (similar to the inner magnetic core 22 described above), an outer magnetic core 34 (similar to the outer magnetic core 24 described above), a primary winding 36 (similar to the primary winding 26 described above), an electrical stress ring 37, and a secondary winding 38. The inner and outer magnetic cores 32, 34, the primary winding 36, the electrical stress ring 37 and the secondary winding 38 are enclosed in dielectric 39 (similar to the dielectric 29) to form a coaxial structure. The secondary winding 38 is a tapered structure comprising: a first secondary winding portion 38a that is tapered and slopes, in a first direction, away from the outer magnetic core 36 and towards the electrical stress ring 37; and a second secondary winding portion 38b that is tapered and slopes, in a second direction different to the first direction, away from the electrical stress ring 37 and towards the inner magnetic core 32. The first and second secondary winding portions 38a, 38b are provided within the same coaxial space. The electrical stress ring 37 comprises a radiussed edge, wherein the first and second secondary winding portions 38a, 38b are electrically connected via the radiussed edge. The provision of a radiussed edge avoids providing a point that would increase electrical stress. A split or gap is provided in the radiussed edge of the electrical stress ring 37 to prevent a short-circuit. The electrical stress ring may act as a turn of the secondary winding (e.g. as a result of the provision of the split or gap in the radiussed edge). The primary winding 36 may be connected (e.g. on the left of the Tesla transformer structure 30 shown in Figure 3) to a Tesla driver (such as the driver 16 described above). Similarly, the secondary winding 38 may be connected to an external load (such as the load 18 described above). Thus, the Tesla transformer 30 may be used to provide the primary coil 12 and secondary coil 14 of the system 10 described above. As described above, the Tesla transformer 30 has a folded secondary winding. The folding enables the number turns provided by the secondary windings to be increased (in the same area), without requiring any other dimensions of an existing Tesla transformer to be changed. For example, there is no requirement to increase the dielectric gap between the inner or outer magnetic cores or to increase the length of the Tesla transformer. The electrical stress ring 37 is provided between the pair of tapered windings 38a, 38b to reduce the E-field and hence to reduce the chance of breakdown due to high electrical voltage. The positioning of the stress ring is discussed in detail below. Figure 4 is a plot, indicated generally by the reference numeral 40, showing a voltage distribution in accordance with an example embodiment. Specifically, the plot 40 shows the voltage distribution between the inner core 32 and the outer core 34 of the Tesla transformer 30 described above. As shown in the plot 40, the electric field across the coaxial structure of the Tesla transformer between the inner and outer cores is non-linear. It may be advantageous to position the electrical stress ring at a mid-point between voltages at the inner and outer magnetic cores. However, as shown in the plot 40, the mid-point of the voltages is not at the geometric mid-point of the coaxial structure. A further problem is that the first secondary winding portion 38a typically has more copper length than the second secondary winding portion 28b, since the first secondary winding portion is wound around a larger diameter. Thus, placing the electrical stress ring 37 in the dielectric middle would cause there to be more DC resistance in the first secondary winding portion 38a than in the second secondary winding portion 38b. Figure 5 is a cross-section showing a portion of a Tesla transformer, indicated generally by the reference numeral 50, in accordance with an example embodiment. The portion of the Tesla transformer 50 shown in Figure 5 includes the inner magnetic core 32, the outer magnetic core 34, the primary winding 36, and the electrical stress ring 37 described above. The Tesla transformer 50 also comprises a secondary winding 58 having a first secondary winding portion 58a that is tapered and slopes, in a first direction, away from the outer magnetic core 36 and towards the electrical stress ring 37; and a second secondary winding portion 58b that is tapered and slopes, in a second direction different to the first direction, away from the electrical stress ring 37 and towards the inner magnetic core 32. Although the secondary winding portions 58a and 58b are similar to the secondary Thus, the secondary winding portions 38a and 38b respectively discussed above, there are some differences. In the Tesla transformer 50, the electrical stress ring 37 is placed closer to the inner magnetic core 32 than the outer magnetic core 36 (so that the electrical stress ring is not at the geometric centre). For example, the electric stress ring 37 may be at a position 30% between the inner and outer magnetic cores, although other dimensions are possible. Whilst the actual value (30% in this example) would typically be based, at least in part, on the geometry of the Tesla transformer, there may be other factors or other areas of high stress that affect the gradient of the electrical field. For example, a radiussed end may be provided on the inner coaxial conductor (as shown in Figure 4, for example) that may change the electrical field gradient. Furthermore, in order to balance the stress ring in the electrical circuit, thicker gauge wire is used for the first secondary winding portion 58b than for the second secondary winding portion 58b. For example, 30% of the total secondary circuit electrical resistance may be in the first secondary winding portion 58a, matching the position of the electrical stress ring relative to the inner and outer magnetic cores. The thicker gauge wire also decreases the circuit losses due to the higher cross-sectional area of the copper wire. Note that 30% parameter is provided by way of example only. Different values for the geometric position and electrical resistances could be used, provided that they are matched. As described above, first secondary winding portion 58a of the Tesla transformer 50 has provides a lower unit electrical resistance path than the second secondary winding portion 58b. This may be achieved by providing a thicker gauge wire (as described above), but alternative implementations are possible. It is noted, for example, that a disadvantage with using thicker gauge wire is that it can be more difficult to turn. Figure 6 is a cross-section showing a portion of a Tesla transformer, indicated generally by the reference numeral 60, in accordance with an example embodiment. The portion of the Tesla transformer 60 shown in Figure 6 includes the inner magnetic core 32, the outer magnetic core 34, the primary winding 36, and the electrical stress ring 37 described above. The Tesla transformer 60 also comprises a secondary winding 68 having a first secondary winding portion 68a that is tapered and slopes, in a first direction, away from the outer magnetic core 36 and towards the electrical stress ring 37; and a second secondary winding portion 68b that is tapered and slopes, in a second direction different to the first direction, away from the electrical stress ring 37 and towards the inner magnetic core 32. In common with the Tesla transformer 50 described above, the electrical stress ring 37 of the Tesla transformer 60 is placed closer to the inner magnetic core 32 than the outer magnetic core 36 (so that the electrical stress ring is not at the geometric centre). In addition, in order to balance the stress ring in the electrical circuit, the first secondary winding portion 68a comprises a parallel connection of two or more windings to provide said lower unit electrical resistance path when compared with the second secondary winding portion 68b. The provision of a parallel connection of windings results in the secondary winding portion 68a having a lower resistance than would be provided by a single winding. Thus, the Tesla transformer 60 is electrically similar to the Tesla transformer 50. The invention also enables the output power of a Tesla transformer to be increased by layering two or more secondary winding together, thereby reducing DC losses. This can be incorporated into a folded Tesla transformer (as described above), but can also be incorporated into other (non-folded) Tesla transformer designs. Figure 7 is a cross-section showing a portion of a Tesla transformer, indicated generally by the reference numeral 70, in accordance with an example embodiment. The Tesla transformer 70 comprises the inner magnetic core 32, the outer magnetic core 34, and the primary winding 36 described above. The Tesla transformer 70 also comprises a secondary winding 78 comprising a parallel connection of two or more windings. The parallel windings provide a lower unit electrical resistance path that a similar single winding. The inner and outer magnetic cores 32, 34, the primary winding 36, and the secondary winding 78 are enclosed in dielectric 39 to form a coaxial structure. As discussed above, the primary winding 36 may be connected (e.g. on the left of the Tesla transformer structure 30 shown in Figure 3) to a Tesla driver (such as the driver 16 described above). Similarly, the secondary winding 78 may be connected to an external load (such as the load 18 described above). Thus, the Tesla transformer 70 may be used to provide the primary coil 12 and secondary coil 14 of the system 10 described above. As discussed above with reference to Figure 6, the principles of providing a parallel connection of two or more windings (as discussed with reference to Figure 7) can be combined with the principles of providing an electrical stress ring and providing first and second folded secondary tapered winding portions. Figure 8 is a cross-section, indicated generally by the reference numeral 80, showing an aspect of Tesla transformer design in accordance with an example embodiment. The Tesla transformer 80 comprises the inner magnetic core 32, the outer magnetic core 34, and the primary winding 36 described above. The Tesla transformer 80 also comprises a secondary winding 88 discussed further below. The inner and outer magnetic cores 32, 34, the primary winding 36, and the secondary winding 88 are enclosed in dielectric 39 to form a coaxial structure. As discussed above, the primary winding 36 may be connected to a Tesla driver (such as the driver 16 described above). Similarly, the secondary winding 78 may be connected to an external load (such as the load 18 described above). Thus, the Tesla transformer 80 may be used to provide the primary coil 12 and secondary coil 14 of the system 10 described above. The secondary winding 88 is a tapered structure comprising: a first secondary winding portion 88a (similar to the first secondary winding portion 38a described above) that is tapered and slopes, in a first direction, away from the outer magnetic core 36 and towards a first electrical stress ring 87a (that is similar to the electrical stress ring 37 described above); a second secondary winding portion 88b that is tapered and slopes, in a second direction different to the first direction, away from the first electrical stress ring 87a and towards a second electrical stress ring 87b, a third secondary winding portion 88c that is tapered and slopes, in the first direction, away from the second electrical stress ring 87b and towards a third electrical stress ring 87c; and a fourth secondary winding portion 88d that is tapered and slopes, in the second direction, away from the third electrical stress ring 87c and towards the inner magnetic core 32. The first, second, third and fourth secondary winding portions are provided within the same coaxial space. The first, second and third electrical stress rings 97a, 87b and 87c may be identical and may each be similar to the electrical stress ring 37 described above. For example, each electrical stress ring may comprises a radiussed edge, wherein the respective second secondary winding portions are electrically connected via the radiussed edge. A split or gap is provided in the radiussed edge of each electrical stress ring to prevent a short-circuit. Each electrical stress ring may act as a turn of the secondary winding (e.g. as a result of the provision of the split or gap in the radiussed edge). The primary winding 36 of the Tesla transformer 80 may be connected (e.g. on the left of the Tesla transformer structure 80 shown in Figure 8) to a Tesla driver (such as the driver 16 described above). Similarly, the secondary winding 88 may be connected to an external load (such as the load 18 described above). Thus, the Tesla transformer 80 may be used to provide the primary coil 12 and secondary coil 14 of the system 10 described above. Example embodiments have been described above that include multiple folded secondary winding portions and either one electrical stress ring (see the Tesla transformers 30, 50 and 60) or three electrical stress rings (see the Tesla transformer 80). In principle, any number of electrical stress rings could be provided. For example, a Tesla transformer may include two electrical stress rings (coupling first, second and third folded secondary winding portions), four electrical stress rings (coupling, second, third, fourth and fifth folded secondary winding portions), or more electrical stress rings. By way of example, Figure 9 is a cross-section, indicated generally by the reference numeral 90, showing an aspect of Tesla transformer design in accordance with an example embodiment The Tesla transformer 90 comprises thf .inner magnetic core 32, the outer magnetic core 34, and the primary winding 36 described above. The Tesla transformer 90 also comprises a secondary winding 98 discussed further below. The inner and outer magnetic cores 32, 34, the primary winding 36, and the secondary winding 98 are enclosed in dielectric 39 to form a coaxial structure. The secondary winding 98 is a tapered structure comprising: a first secondary winding portion 98a that is tapered and slopes, in a first direction, away from the outer magnetic core 36 and towards a first electrical stress ring 97a; a second secondary winding portion 98b that is tapered and slopes, in a second direction different to the first direction, away from the first electrical stress ring 97a and towards a second electrical stress ring 97b, and a third secondary winding portion 98c that is tapered and slopes, in the first direction, away from the second electrical stress ring 97b and towards the inner magnetic core 32. The first, second and third secondary winding portions are provided within the same coaxial space. The first, second and third electrical stress rings 97a, 87b and 87c may be identical and may each be similar to the electrical stress ring 37 described above. Features of various example embodiments described above may be combined. For example, the principles of providing a parallel connection of two or more windings can be combined with the principles of providing a plurality of electrical stress rings and a plurality of secondary tapered winding portions. By way of example, Figure 10 is a cross-section showing a portion of a Tesla transformer, indicated generally by the reference numeral 100, in accordance with an example embodiment. The Tesla transformer 100 comprises the inner magnetic core 32, the outer magnetic core 34, and the primary winding 36 described above. The Tesla transformer 100 also comprises a plurality of electrical stress rings 107 and a secondary winding 108. The inner and outer magnetic cores 32, 34, the primary winding 36, the electrical stress rings 107, and the secondary winding 108 are enclosed in dielectric 39 to form a coaxial structure. The secondary winding 108 is a tapered and folded structure comprising: a first secondary winding portion 108a that is tapered and slopes, in a first direction, away from the outer magnetic core 36 and towards a first electrical stress ring 107a; a second secondary winding portion 108b that is tapered and slopes, in a second direction different to the first direction, away from the first electrical stress ring 107a and towards a second electrical stress ring 107b, and a third secondary winding portion 108c that is tapered and slopes, in the first direction, away from the second electrical stress ring 107b and towards the inner magnetic core 32. The first, second and third secondary winding portions are provided within the same coaxial space. The first, second and third electrical stress rings 107a, 107b and 107c may be identical and may each be similar to the electrical stress ring 37 described above. One or more of the secondary winding portions 108 may comprise a parallel connection of two or more windings. As discussed above, such parallel windings can be used to provide a lower electrical resistance path that a similar single winding. For example, the second secondary winding portion 108b may comprise a parallel connection of two windings (to provide a lower resistance than the third secondary winding portion 108c) and the first secondary winding portion 108a may comprise a parallel connection of three of more windings (to provide a lower resistance than the second secondary winding portion 108b). By way of example, Figure 11 is a close up view, indicated generally by the reference numeral 110, of an example implementation of a stress ring that may be used in some example embodiments. Specifically, Figure 11 shows an example end view looking from the right of the cross-section of Figure 5 towards the Tesla transformer. The view 110 includes the stress ring 37, the, first secondary winding portion 58a (that is tapered and slopes, in a first direction, away from the outer magnetic core 36 and towards the electrical stress ring 37), and the second secondary winding portion 58b (that is tapered and slopes, in a second direction different to the first direction, away from the electrical stress ring 37 and towards the inner magnetic core 32). The inner magnetic core 32 and the outer magnetic core 34 are not visible in Figure 11. As shown in Figure 11, the example implementation of the stress ring 37 includes radiussed edge 112. The first and second secondary winding portions 58a, 58b are electrically connected via winding terminations 114 provided near the radiussed edge 112 (as noted above, the provision of the radiussed edges 112 avoids providing a point that would increase electrical stress). A split or gap 116 is provided in the radiussed edge to prevent a short-circuit. The electrical stress ring 37 may act as a turn of the secondary winding (e.g. as a result of the provision of the split or gap 116 in the radiussed edge). Of course, the arrangement of Figure 11 can be modified where further secondary windings are provided. Example embodiments are described above in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein. Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.

Claims

1. A Tesla transformer comprising:an inner magnetic core;an outer magnetic core;a primary winding;a secondary winding comprising a parallel connection of two or more windings.

2. A Tesla transformer as claimed in claim 1, wherein the secondary winding is encased in a dielectric material to form a coaxial structure.

3. A Tesla transformer as claimed in claim 1 or claim 2, further comprising one or more inputs configured to enable an input signal from a driver section to be discharged through the primary winding.

4. A Tesla transformer as claimed in claim 1 or claim 2, further comprising a Tesla driver section for providing an input signal to be discharged through the primary winding.

5. A Tesla transformer as claimed in any one of the preceding claims, furthercomprising an electrical stress ring, wherein the secondary winding comprises: a first secondary winding portion that is tapered and slopes, in a first direction, away from the outer magnetic core and towards the electrical stress ring; and a second secondary winding portion that is tapered and slopes, in a second direction different to the first direction, away from the electrical stress ring and towards the inner magnetic core, wherein one of said first and second secondary winding portions comprises said parallel connection of two or more windings.

6. A Tesla transformer as claimed in claim 5, wherein the electrical stress ring is positioned at a mid-point between voltages at the inner and outer magnetic cores.

7. A Tesla transformer as claimed in claim 5 or claim 6, wherein the secondary winding is encased in a dielectric material to form a coaxial structure and wherein the electrical stress ring is positioned at a mid-point between voltages at inner and outer conductors of the coaxial structure.

8. A Tesla transformer as claimed in any one of clams 5 to 7, wherein the electrical stress ring comprises a radiussed edge, wherein the first and second secondary winding portions are electrically connected via the radiussed edge.

9. A Tesla transformer as claimed in any one of claims 5 to 8, wherein the electrical stress ring acts as a turn of the secondary winding.

10. A Tesla transformer as claimed in any one of claims 5 to 9, further comprising a second electrical stress ring, wherein the secondary winding comprises a third secondary winding portion, wherein the second secondary winding portion slopes towards the second electrical stress ring and the third secondary winding portion slopes, in the first direction, away from the second electrical stress ring and towards the inner magnetic core, wherein one or more of said first, second and third secondary winding portions comprising said parallel connection of two or more windings.

11. AT esla transformer as claimed in claim 10, further comprising a thirdelectrical stress ring, wherein the secondary winding comprises a fourth secondary winding portion, wherein the third secondary winding portion slopes towards the third electrical stress ring and the fourth secondary winding portion slopes, in the second direction, away from the third electrical stress ring and towards the inner magnetic core, wherein one or more of said first, second, third and fourth secondary winding portions comprising said parallel connection of two or more windings.

12. A Tesla transformer as claimed in any one of claims 5 to 11, further comprising a plurality of electrical stress rings, wherein the secondary winding comprising a plurality of secondary winding portions.18Intellectual Property jQffieeDn no:GB2416234.9Ito 12Examiner: Ian ReesDate of search: 9 April 2025Claims searched:Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular reference A - CN 107025985 A NORTHWEST INST NUCLEAR TECH. A - "Analytical design and simulation of a 9.3 GW Tesla Transformer for HPM sources", GN Appiah et al, IEEE Transactions on Plasma Science, vol 50, no 12, December 2022Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if combined with one or more other documents of same category. P Document published on or after the declared priority date but before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:Search of GB. EP, WO &US patent documents classified in the following areas of the UKCWorldwide search of patent documents classified in the following areas of the IPC____________F41H; H01F_____________________________________________________The following online and other databases have been used in the preparation of this search reportSEARCH-PATENT, SEARCH-NPL

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