US3541424A

US3541424A - High voltage generating device

Info

Publication number: US3541424A
Application number: US827118A
Authority: US
Inventors: Hiromitsu Tada; Ryuso Aihara
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 1969-05-19
Filing date: 1969-05-19
Publication date: 1970-11-17
Anticipated expiration: 1987-11-17

Description

1970 HIROMITSU TADA ETAL 3,54ig-i2 HIGH VOLTAGE GENERATING DEVICE Original Filed April 12, 1966 4 Sheets-Sheet 5 D. C. 00 rPur Vol. TAG! INVENTORS HmoM/rsu 72104 BY .Qruso A/HAM 0 .5 z q /6 0W0 mses Cflfiora/EIS Z Ma page! 7345/: Ar revue-v.5

Nov. 17, 1970 HIROMITSU TADA ETAL 3,541,424

HIGH VOLTAGE GENERATING DEVICE Original Filed April 12, 1966 4 Sheets-Sheet L INVENTORS' H/eaM/nsu 7740A BY Evuso A/HARA CAEOTHE$CAEOTMES THE/z Arraeue'ms United States Patent Int. Cl. H02m 7/00; H01f 27/28 US. Cl. 321-8 14 Claims ABSTRACT OF THE DISCLOSURE A high voltage generating device having a closed loop magnetic core made of an electric insulating and magnetic permeable material having a specific resistance of -10 0 cm. A primary coil is wound around a portion of the core and a plurality of secondary coils are wound around different portions of the core and electromagnetically coupled with the primary. The secondary coils are connected in a sequential series from the grounding point to additively combine their output voltages and the respective portions of the core about which they are wound are potentialized with substantially the same voltage as the output voltage of the corresponding secondary coil with or without rectification.

This is a continuation of application Ser. No. 542,052 filed Apr. 12, 1966, now abandoned.

This invention relates to a high voltage generating device in which an electric-insulating magnetic-permeable material is used for the transformer core. This invention also relates to a high voltage generating device in which a compensating coil is provided to strengthen the magnetic coupling of the transformer core by the use of said electric-insulating magnetic-permeable material.

In the case of the high voltage generating device heretofore in use, a primary coil and secondary coil are wound around one transformer core, and when the input voltage is applied to the primary coil, it is raised to a higher voltage in the secondary coil. An electric-conductive me tallic material such as a silicon steel plate is used for the transformer core, so that it is necessary to insulate the primary coil, the secondary coil and the transformer core from each other in order to prevent the higher voltage generated in the secondary coil from leaking to the primary coil or the core. However, as the dielectric strength of electric insulating materials is not infinite, it has been impossible to obtain a voltage higher than 300 kv. in this way.

As an improvement over this system, there is the socalled cascade transformer type high voltage generator, which comprises a plurality of transformers placed together one upon another. The tertiary coil provided in the first step transformer of the lowest voltage is connected to the primary coil wound around the transformer coil of the second step to generate a higher voltage in the secondary coil of the second step transformer while the tertiary coil of the second step transformer is connected to the primary coil of the third step transformer core. In a multi-step transformer assembled in this way, each transformer core is excited by the tertiary coil which is wound around and electrically insulated from the transformer core one step below, and the transformer core of each step is insulated from the potential of the transformer core one step below, so that all the voltages generated in the transformers up to the top one may not leak to transformer cores.

In the case of this system, it may be said that theoretically any high voltage can be obtained by placing together as many transformers as necessary one upon another. In

actuality, however, leakage of magnetic flux takes place in coupling the transformer core of each step between the core and the primary coil and tertiary coil, so that there is a limit to the electric energy given to the lowest step transformer and up by the highest step transformer. It has been found impossible to generate a voltage higher than 2 mv. in this way.

The present invention provides a drastic improvement with respect to the shortcomings of the high voltage generator of said cascade transformer type. The high voltage boosting transformer used in the present invention has a closed magnetic core made of a magnetic-permeable material, such as a ferrite, which has a high electric specific resistance value of about 10 -10 9 cm. Around such a closed magnetic core are wound secondary coils for the generation of high voltage distributed over the core without necessity for concern in particular about electrical insulation from the core. The higher voltage generated in the secondary coils leak into the core through the electric resistance of the core, but this is a small loss of electric energy since it is only about 6 ,ua. where a D.C. voltage of 500 kv. is generated by a transformer of this type using a ferrite having a core section of about cm. and leg length of 80 cm. It does not therefore interfere with the boosting of voltage. To the contrary, it efiects improvement with respect to the instability of potential distribution due to high impedance often observed with the generator of such a high voltage.

Another feature of the present invention is as follows: The magnetic-permeable material used in this invention as stated already is a material having a magnetic permeability of about 3000-6000. It is a comparatively large transformer core having a magnetic path length of 200 cm. If a primary coil is wound only at an end of the core, therefore, it is impossible to excite the whole of the magnetic path uniformly. Considerable electric energy may be transmitted to secondary coils for higher voltage generation in the neighborhood of the primary coil. However, the leakage inductance of secondary coils become greater as they are separated farther from the primary coil. The output voltage of the secondary coils comes down extremely fast upon the application of a load and rises extremely fast upon removal of the load. The feature of the present invention relates to a method of compensating for this so-called voltage regulation.

The magnetic coupling between the primary coils and the secondary coils is effected by providing a plurality of compensating coils distributed in the axial direction of the ferrite core and wound concentrically with the secondary coils around the ferrite core around which the secondary coils for high voltage generation are wound and by coupling adjacent compensating coils magnetically, electrical coupling and magnetic coupling being effected alternately in this way, to compensate for the magnetic coupling of primary coils and secondary coils while maintaining sufficient electrical insulation on the whole for the high voltage generated.

The aforementioned essential features of the present invention will be made clearer in a definite way by explanation to be given hereinafter with reference to an embodiment of t e invention.

An object of t e present invention is, as can be seen from the essential features of the invention already mentioned, to obtain a high voltage generating device with a low loss of electric energy.

Another object of the present invention is to obtain a transformer with little transformer core loss.

Another object of the present invention is to obtain a transformer which does not require heavy electrical insulation as ordinary transformers do between secondary coils for high voltage generation and the core.

Another object of the present invention is to obtain 3 a high voltage by using a simple construction which employs a unique means to potentialize the transformer core.

Another object of the present invention is to obtain a boosting circuit which requires little voltage regulation.

' Another object of the present invention is to maintain high potential stabilized by having the core itself have potential distribution.

Another object of the present invention is to provide sufficient magnetic flux to secondary coils for high voltage generation by means of compensating coils.

Still another object of the present invention is to obtain a D.C. high voltage generating device which is a small size and which is portable when necessary. Furthermore, still another object of the present invention is to make the device smaller by making use of a ferrite which i of little core loss at high frequencies.

A characteristic of the present invention is that it is a high voltage boosting transformer which comprises a transformer core potentialized by the voltage output of the transformer and'made of an electric-insulating and magnetic-permeable material of a specific resistance of -10 9 cm., and has its primary coil wound on the transformer core near its point of ground potential, and a high voltage generating or secondary coil wound also on the transformer core.

Another characteristic of the present invention is that it is a high voltage boosting transformer as mentioned above which has a means to impart to at least one part of the transformer core, the voltage secondary by the high voltage generating coils or a voltage induced by this voltage.

Another characteristic of the present invention is that it is a high voltage boosting transformer as mentioned above, which has a compensating coil wound concentrically or coaxially with the primary coil and a plurality of compensating coils coupled therewith and wound concentrically with the high voltage generating or secondary coils. All of the compensating coils have a means to connect or couple each pair of adjacent compensating coils in such a manner that the magnetic flux induced in the transformer core by each of the compensating coils is in a direction which complements that of the other.

Still another characteristic of the present invention is that it is a high voltage boosting transformer which comprises a plurality of inner compensating coils coaxially wound and distributed along one and the same cylindrical surfaces about the transformer core, and a plurality of outer compensating coils coaxially wound on a cylindrical surface larger than that on which the inner circumferential compensating coils are wound. The inner and outer coils are axially aligned for magnetic coupling, and a means is provided for connecting one of the pair of axially aligned inner and outer compensating coils, to a one of the adjacent pair of axially aligned compensating coils, and a means for connecting the other coil of said pair to one coil of the other adjacent pair of compensating coils.

These together with other objects and features of this invention will become more readily apparent from the following detailed description and the accompanying drawings.

The principles of the present invention are equally applicable to an alternating current high voltage device as well as direct current high voltage generating devices and many adaptations and alterations can be made without departing from the spirit or scope thereof.

FIG. 1 is a circuit diagram of a D.C. high voltage generating device illustrating an embodiment of the present invention.

FIG. 2 is the schematic diagram of a high voltage rectification circuit used in an embodiment of the present invention.

FIG. 3 is a sectional view in side elevation showing the layout of the ferrite core, secondary coils and compensating coils used in an embodiment of the present invention.

FIGS. 4a and 4b are plan and front views respectively showing a ferrite core disc.

FIG. 5 is a graph of the B-H characteristic curve of the ferrite core.

FIG. 6 is a graph showing the degree of coupling between the primary coil and the secondary coil of an embodiment of the present invention.

FIG. 7 is a graph of the load characteristic curve showing variations of output voltage due to load current in an embodiment of the present invention.

FIG. 8 is a side view in partial section showing the appearance, and a part of the interior, of a D.C. high voltage generating device of 400 kv., l0 ma., which is an embodiment of the present invention.

FIG. 9 is a plan of the cross section taken at the line A-A of the D.C. high voltage generating device shown in FIG. 8.

It should be noted that the present invention is by no means limited to the following description of an embodiment which is mentioned only as an example.

First, the basic principle, with reference to the wiring diagram, of an embodiment of the present invention which is a D.C. high voltage generating device having an output of 400 kv., l0 ma., will be explained. The high voltage generating secondary coils 20-39 are divided into 20 step blocks or different coils and the secondary coil block of each step is capable of generating 10 kvp. The blocks of 20 steps are installed on the ferrite cores 40-43 outlined in FIG. 1, and rectification is effected by means of the Greinacher circuits 44-63.

In more detail,

ferrite cores

42 and 43 are made by putting together, one upon another, ferrite discs of materials, to be explained hereinafter, to form cylinders used as two legs and as the two opposite sides of a magnetic loop. These legs are connected together with rectangular ferrite blocks 40 and 41 to form a magnetic loop. These two opposite side ferrite blocks 40 and 41 have the same potential as the output D.C. high voltage and the ground potential respectively. The primary coil 64 for feeding electric power is wound 22 turns on said ferrite core 41 near its grounding point. A high frequency power source is connected to both terminals of the primary coil 64, though this is not shown in the drawing. In the present embodiment, a high frequency power source of a frequency of 1 kc./s. and output of 5 kva. was used. For such a high frequency power source, a commonly known high frequency oscillator generating frequency ranging from about 1 kc./s.-l00 kc./s. is sufficient. In the present embodiment, current of -60 c./s. from a commercial AC. power source was converted into D.C. of 0-90 v. by means of a silicon rectifier, and a frequency converter was used to convert this into AC. of 1 kc./s., 0-180 v., by a silicon controlled rectifier inverter.

A secondary voltage of 10 kvp., at the highest, is induced in each of the secondary coils 20-39 by the variation of the magnetic flux induced in the interior of the ferrite cores 40-43 by the input coil 64. In FIG. 1,- the blocks of 20 steps are divided into groups of 10 steps each and secondary coils 20-29 are provided on the ferrite core 42 and secondary coils 30-39 on the ferrite core 43. A secondary coil is wound 960 turns around the block of one step.

Both ends of the secondary coils 20-39 for high voltage generation, are connected with the so-called Greinacher circuits 44-63 which effect voltage doubling rectification. The internal wiring of the Greinacher circuits 44-63 is shown in FIG. 2.

Both ends of said secondary coils 20-39 are connected to the input terminals 65 and 66 of the Greinacher circuits respectively, and the alternating current supplied is rectified by the

rectifiers

69 and 70 and charged to the

condensers

71 and 72, generating D.C. high voltage of 20 kv. at the highest at the

output terminals

67 and 68.

The

rectifiers

69 and 70, are preferably of the silicon cartridge type which withstand voltages of 25 kv. and

forward current of 60 ma. max. For the condensers, two ceramic condensers, 4000 pf., which withstand voltages of kv. placed in parallel are used. As shown in FIG. 1, the output terminals 1-19 of the Greinacher circuits 54- 63 of all the steps are connected to the Greinacher

circuits output terminals

1, 2, 3 17, 18, 19 connected to the secondary coils 20-39 provided on the opposite ferrite core 43 respectively, so that the D.C. high voltage generated by the Greinacher circuits is integrated and a minus D.C. high voltage of 400 kv. maximum in total is obtained at the output terminal 73 of the Greinacher circuit 63 of the topmost step.

As shown in FIG. 1, the Greinacher circuits are connected alternately up to the higher voltage ones starting from the side or bottom at the ferrite core 41 around which the primary coil 64 is wound. Between two adjacent circuits of the secondary coils 20-29 and Greinacher circuits 44-53 provided on the ferrite core 42 for example (for instance, between the secondary coils and 26 and Greinacher circuits 49 and 50) the potential difference generated in the corresponding Greinacher circuit on the opposite leg such as circuit 59 is applied to the ferrite core 43. It is therefore sufficient if the electrical insulation provided between these

secondary coils

25 and 26 and

Greinacher circuits

49 and 50 is such that it can withstand the output of each of said

Greinacher circuits

49 and 50 is such that it can withstand the output of each of said Greinacher circuits of D.C. 20 kv. plus the voltage generated by its own circuit.

The terminal 73 of the Greinacher circuit 63 is connected to the high voltage generating terminal 75 via resistance 74. On the other hand, the terminal 73 is connected to the extremity 76 of the ferrite core 43, while the opposite extremity 77 of the ferrite core 42 is grounded with the output terminal 78 on the plus side of the Greinacher circuit 44, so that the aforementioned D.C. high voltage generated causes direct current of several ,ua. to flow in the

ferrite cores

43 and 41 and 40 and 42. Because of this, the

ferrite cores

43 and 41 and 40 and 42 have a uniform potential distribution in the direction from the top part 76 to the bottom part 77, and this potential distribution becomes about equal to the potential of each of the secondary coils. In consequence, it is simple in the case of this embodiment to effect electrical insulation between the secondary coils, Greinacher circuits, ferrite cores and the compensating coils which are explained later.

If the terminal 73 of the Greinacher circuit 63 is not connected to an extremity 76 of the ferrite core, sparks will take place due to electrostatic induction between the

ferrite cores

42 and 43 and the secondary coils 20-39 or the compensating coils to be explained hereinafter.

It is preferable to connect the terminals 7988 at one end of the

secondary coils

20, 22, 24, 26, 28, 30, 32, 34, 36 and 38 to the portion of the ferrite core where they are installed or wound respectively shown in FIG. 1 of the drawings, since the potential distribution of the ferrite core becomes equal to that of the secondary coils as already mentioned and the potential distribution is stabilized. For practical purposes, however, it is permissible if the terminal 73 alone is connected to one point in the top part 76 of the ferrite core.

The above-mentioned D.C. high voltage generated, can be measured by measuring the current flowing in the high resistance 89 of FIG. 1 by means of an ammeter 90.

The compensating coils 91-110 constitute another essential feature of the present invention.

Compensating coils 91 and 101 are wound around the ferrite core 41 around which the primary coil '64 is wound. Around the ferrite core 42, around which secondary 21, 23, 25, 27 and 29 are wound, and in the neighborhood of the

secondary coils

21, 23, 25, 27 and 29, and under these secondary coils, are wound compensating coils 92- 100. Compensating coils 92 and 93, compensating coils 94 and 95, compensating

coils

96 and 97, and compensating coils 98 and 99 are being wound concentrically or coaxially and in one and the same position with respect to the ferrite core 42. Compensating coil 91 is connected to compensating coil 92, coil 93 is connected to 94, 95 to 96, 97 to 98 and 99 to 100. Compensating coils 101- 110 are also arranged in a similar way. Each one of these compensating coils is wound 26 turns. The compensating coils are alternately arranged in the above-mentioned manner; compensating coil 95 for instance faces or is adjacent secondary coil 23 and compensating coil 96 is adjacent secondary coil 25, as may be seen from FIG. 1. It is therefore necessary that secondary coils 23-25 and compensating

coils

95 and 96 be insulated to withstand the potential difference between

secondary coils

23 and 25. In order to make this insulation voltage stabilized, either one of the connections of compensating

coils

95 and 96 is connected to one terminal 81 of secondary coil 24 which is at about the intermediate potential between

secondary coils

23 and 25. As shown in FIG. 1, one side of the wiring connection of each connected set of compensating coils is connected to one terminal of one of the even numbered secondary coils -88.

Insulation between two adjacent compensating coil loops, the loop of compensating coils and 96 and the loop of compensating

coils

97 and 98 for example, particularly the insulation between compensating

coils

96 and 97, is made of such electrical insulation that can withstand the potential difference between secondary coil 23 and secondary coil 27, because the compensating coils are wound in positions facing secondary coil 23 and secondary coil 27.

FIG. 3 is a sectional view showing the arrangement of these secondary coils and compensating coils and the ferrite core and electrical insulation between them. 42 is a ferrite core of a cylinder having a diameter of mm. This ferrite core 42 is made of discs, each of which is, as shown in FIG. 4, 100 mm. in diameter and 25 mm. in thickness. The disc has a fluid fiow hole 111 and three assembling holes 112 in its central part. Three nylon shafts are put through the assembling holes 112 and the discs are pressed tight from top and bottom for assembling. Said fluid flow hole is provided for the purpose of circulating a cooling liquid or gas when the ferrite core becomes heated. In the present embodiment, cooling is effected by a natural flow of Freon gas.

This ferrite core is one of the principal features constituting the present invention. The ferrite cores 40-43 are made of the ferrite of Ni-Zn. A product with a trade name of Ferribrox, made by Tohoku Metal Industrial Co., Ltd, may be used. It is a product having the following electric and magnetic characteristics:

Maximum permeability '=2,800 At 1 mc. magnetic core loss coefiicient tan 0//L=0.260.27X 10- Hysteresis loss coefiicient h =42-47 Specific resistance =4.0 10 9 cm. Magnetic flux density when excited to 10 oersteds The B-H characteristic at 50 C. of this ferrite core is shown in FIG. 5.

In the present embodiment, the maximum magnetic flux density of the ferrite core is 1,680 gauss, and the resistance of the assembled

ferrite cores

42 and 43 are each 10 m0 or more. 113 is a cylinder of metamethyl acrylate used to cover these ferrite cores. Grooves of a 2 mm. depth are made in the wall having a thickness of 5 mm., and compensating coils, 94 and 96 for example as shown in FIG. 3, are wound therein.

A cylinder 114 of metamethyl acrylate is placed thereon concentrically or coaxially, on which compensating coils 95 and 97 are wound in a like manner.

The gap between the

cylinders

113 and 114 is kept at 10 mm. Concentrically with them is installed a bobbin 115 of metamethyl acylate, around which secondary coils 23-26 for example are wound. The gap between the cylinder 114 and the bObbin 115 is mm.

The maximum magnetic flux density of the ferrite cores 40-43 is about 1,680 gauss, lower than that of the silicon steel core heretofore used, and in addition, the magnetic path length will be about 200 cm. for a high voltage generator of 400 kv. When it is used for a boosting transformer core without said compensating coils 91- 110, therefore, leakage magnetic flux increases and magnetic coupling between primary coils and secondary coils decreases. When a load is taken from a load circuit of high voltage generated by the boosting transformer, power of D.C. 400 kv., ma., for example, as shown by curve 116 in FIG. 6, will be obtained. The vertical axis of FIG. 6 represents in percentage the degree of magnetic coupling between primary coils and secondary coils, while the horizontal axis represents the reference numbers of the output terminals of the Greinacher circuits 54-63 shown in FIG. 1.

It is shown that in the absence of compensating coils 101-110, the terminal 2 on the horizontal axis, for example, in FIG. 6 generates only 80% of the expected output voltage generated by secondary coil 30 and rectified by Greinacher circuit 54 of FIG. 1. This tendency becomes more remarkable as the distance from the primary coil 64 becomes greater. As shown in FIG. 6, the voltage at the terminal 73 induced by the secondary coil 39 is only 47%. However, if compensating coils 91- 110 are used in the same way as already mentioned, the degree of coupling between primary and secondary coils is remarkably improved, it being 100% at

terminal

2, 98% at

terminal

10 and 93 at terminal 73 as indicated by the curve 117 in FIG. 6. In case D.C. output of 400 kv. is taken from the D.C. high voltage generator of this example, the voltage somewhat decreases as load current is increased, as shown in FIG. 7, the DC. output voltage becoming 370 kv. when the load current is 10 ma. If compared with a generator without compensating coils, however, it clearly shows a remarkable improvement. The curve 119 of FIG. 7 is a curve showing the decrease in the output voltage of the generator without compensating coils, given for the sake of comparison with the generator with compensating coils.

In the present embodiment, the voltage pulsating percentage at the time an output of 400 kv., l0 ma., is taken out also shows an improvement, it being approximately 2%.

FIG. 8 is a side view showing the appearance, and a part of the interior, of the DC. high voltage generating device of 400 kv., 10 ma., of the present embodiment, and FIG. 9 is a plan of the section taken at A-A of FIG. 8 and viewed in the direction of the arrow.

120 is the corona shield for the high potential portion or area, made of aluminum. Its surface is finished smooth. 121 is the insulating pressure tank of a wall thickness of 5 mm., made of fiber reinforced plastics. It has a creeping distance of about 1,200 mm., and can fully withstand a D.C. voltage of 400 kv. 122 is the flange, 25 mm. thick, installed on the inner surface of the tank. 123 is the gas seal gasket. By the lid 135, atmospheric pressure is maintained above this gasket 123 and Freon gas CCI F pressurized to 1 kg./cm. plus atmospheric pressure under the gasket. 74 is the protective resistance, 500 k9. 124 is the upper insulating plate, 125 is the metamethyl acrylate plate for carrying the

condensers

71 and 72 of the

rectifiers

69 and 70. 126 is the pole of metamethyl acrylate to support the interior of the device. Said insulating plate 125 and protective resistance 74 are fixed tothis pole. The upper part of the pole 126 is joined to said insulating plate 125 by means of a bolt, while its lower part is fixed to the rack 128 by means of the metal fitting 127. 71 and 72 are ceramic condensers, 129 the L-shaped metal for their installation, and 130 the gas sealing gasket, tightened by the rack 128 and pressure tank 121 and kept gas-tight. 131 is the rubber wheel and 132 is the coil support, 133

8 the ferrite core support made of stainless steel SUS-27. 134 is the nylon shaft to tighten the coil blocks. 2 legs of each 6 shafts are uniformlytightened to retain board 136. 40-43 are ferrite cores, 64 the primary coil, 20-29 the secondary coils, and 69 and 70 the silicon rectifiers.

This device is assembled on the rack 128 which has wheels. The ferrite cores of insulating material 40-43 are assembled on the core rack 133 attached to this wheeled rack 128. These cores are kept together tightly by means of three nylon shafts put through the holes 112 in the core discs. Around the ground potential part of the core is wound the primary coil 64 whose terminals are connected to the bushing (not shown in the drawing) provided penetrating the rack in the lower part of the rack 128. As shown in FIG. 1, the magnetic compensating coils 101 and 91 of the first step are wound on the primary coil 64. Each of the two legs of the core has 10 secondary coils 20-39 wound around it. The compensating coils 92- 100, 102-110, are wound inside (under) these secondary coils. As shown in FIG. 1, these compensating coils are arranged 5 steps/leg. As shown in FIG. 1, these compensating coils are connected to Greinacher circuits 44- 63 respectively by means of 79-88 to obtain D.C. potential. As may be seen from the wiring shown in FIG. 2, the output of these secondary coils charges the

condensers

71 and 72 via the

rectifiers

69 and 70. The Greinacher circuits 44-63 are connected to the transformer legs alternately in series (FIG. 1). One end 78 is grounded, and all the steps are connected to the same poles so that the output voltage is integrated. The last output terminal 73 is connected to the top part 76 of the ferrite core to give the ferrite core potential gradient. That output terminal is connected to the lid (iron) 135 via the protective resistance 74 of 500 k0, and is connected to the corona shield by a lead wire from its back side.

Thus the present device can generate D.C. voltage of 400 kv. between the rack 128 and the corona shield 120. The interior of the tank is filled, by the method of prior art, with Freon gas (CCl F and pressurized to 1 kg./ cm. plus atmospheric pressure. 89 is the bleeder resistance of 4000 m9 to measure the output voltage between the highest D.C. potential part and the rack.

According to the present embodiment, a high voltage generating device having a D.C. high voltage output of 400 kv., l0 ma., of a comparatively small size of a 71 cm. diameter and 134 cm. height can be obtained.

As has been explained in detail, the present invention provides a high voltage generating device which is easy to insulate electrically, using a transformer core made of an electric-insulating magnetic-permeable material such as a ferrite having specific resistance 10 -10 9 cm. and a magnetic permeability of 3000-6000. Furthermore, a useful high voltage generating device, which has little voltage drop even when the load applied to the generated high voltage is heavy, is provided by improving the degree of coupling between the primary coil and secondary coils when said transformer core of electric-insulating magnetic-permeable material is used, by means of compensating coils which effect multi-step magnetic coupling step by step.

We claim:

1. A high voltage generating device comprising a closed loop magnetic core made of magnetic permeable material having a specific resistance of 10 -10 9 cm., said core grounded at one point and potentialized by the generated output voltage connected at a diagonally opposite point on said core, a primary coil wound around a portion of saidv core adjacent said ground connection point, a plurality of secondary coils wound around different portions of said core and in operable relation with said primary coil and separated in opposed series on opposite sides of said primary coil, connection means to connect said opposed series of secondary coils alternately in a single sequential series on the opposite sides of and progressively from said primary coil to said diagonally opposite potentialized core point and additively combine their respective voltage outputs to obtain said generated output voltage, said first secondary coil of said single sequential series connected to ground.

2. The high voltage generating device of claim 1 characterized in that selected of said secondary coils are connected to the corresponding adjacent portions of said core about which they are respectively wound.

3. The high voltage generating device of claim 1 wherein said closed loop magnetic core has four joined legs each consisting of a number of ferrite discs having a plurality of aligning holes at least two of which have nylon shaft means clamping the discs together, said primary coil on one leg and said series of secondary coils stacked on each adjacent side leg and said fourth leg at the opposite end from said primary coil leg.

4. The high voltage generating device of claim 1 characterized by a plurality of compensating coils wound coaxially with said primary and secondary coils, said compensating coils being in connected parallel pairs and disposed axially along said core, the first compensating coil of two parallel connected pairs wound with said primary coil and one of their respective second coils of said two parallel connected pairs being wound coaxially with one selected initial secondary coil group in each of said opposed series, the first compensating coil of each other parallel pair in turn wound with said previously selected secondary coil group and its respective second coil wound with the next selected secondary coil group of its respective series.

5. The high voltage generating device of claim 3 wherein both series of secondary coils are clamped between opposed acrylic clamp plates mounted between said end legs of said core to fixedly hold said secondary coils.

6. The high voltage generating device of claim 3 wherein each of said ferrite discs having a flow hole through which to circulate coolant fluids through said closed loop magnetic core.

7. The high voltage generating device of claim 4 characterized by connection means between one secondary coil of each selected coil group and its respective compensating coil pair.

8. The high voltage generating device of claim 7 characterized by a core connection between each of said last connection means to said core adjacent the vicinity of said last connection means and said core.

9. The high voltage generating device of claim 1 characterized by said primary coil being supplied with a high frequency current.

10. The high voltage generating device of claim 1 characterized by resistance means connected between said generated output voltage and a high voltage terminal of said device.

11. The high voltage generating device of claim 1 characterized by rectifier circuit means for each secondary coil in said alternately opposed single sequential series to rectify each coil output in said single sequential series.

12. The high voltage generating device of claim 11 characterized in that selected of said secondary coils are connected to the corresponding adjacent portions of said core about which they are respectively wound.

13. The high voltage generating device of claim 4 characterized by rectifier circuit means for each secondary coil in said alternate opposed single sequential series to rectify each coil output in said single sequential series.

14. The high voltage generating device of claim 13 characterized in that selected of said secondary coils are connected to the corresponding adjacent portions of said core about which they are respectively wound.

References Cited UNITED STATES PATENTS 1,776,078 9/1930 Mignot 336-184 XR 1,853,764 4/1932 Fischer 336-170 XR 2,055,346 9/1936 Foster 336- XR 2,756,397 7/1956 Cederstrom et al. 336-185 XR 3,196,345 7/1965 Dobsa 336- XR 3,274,526 9/1966 Emanuelson 336-212 XR 3,356,931 12/ 1967 Welty et al. 323-48 OTHER REFERENCES Bozorth: Ferromagnetism, D. Van Nostrand Co., New Jersey, March 1951, pp. 870-871.

THOMAS J. KOZMA, Primary Examiner US. Cl. X.R.