Magnetic flux coupled voltage multiplication apparatus

An apparatus for producing a very high DC potential output from an AC input. Multiple secondary circuits, each comprised of an individual coil wound about a separate magnetic core, are positioned within the magnetic field of a single primary coil. The output of each secondary circuit is rectified. The output of all secondary circuits is combined in series to provide the high DC potential. The seconary cores are supplied in parallel from the magnetic flux of the primary coil. The primary core and coil form an essentially cylindrical shell, with the secondary cores and coils located within the cylinder interior.

BACKGROUND OF THE INVENTION 
The present invention relates to high voltage power supplies. More 
specifically, the present invention relates to high voltage power supplies 
utilizing a voltage multiplication technique to create a voltage potential 
of sufficient magnitude for use in an electron accelerator. 
Very high potential power supplies in the range of one to two megavolts 
(MV) are required for a number of applications including high power 
electron beam accelerators. Beam accelerators in the range of 50-500 
kilowatts often require acceleration energies of up to 5 megavolts. Often 
a large number of power supplies are needed in order to achieve the 
necessary power to produce the desired electron beam energy. Utilization 
of a large number of power supplies to achieve such power is often 
unmanageable and uneconomical. 
Presently available accelerators, therefore, do not meet the requirements 
of high beam power, high beam energy and economical costs. Some commercial 
power supplies utilized to achieve high voltage energy utilize solid 
dielectric insulation. Some of these power supplies are able to achieve 
the necessary high voltage with a few stages but are still not capable of 
producing the necessary power at an economical cost. 
U.S. Pat. Nos. 3,708,740 and 3,393,114 to Pierson teach transformers which 
are designed to generate large DC potentials. U.S. Pat. No. 2,251,373 to 
Olsson teaches a high tension transformer having a construction similar to 
that of the pierson transformers. A number of serially connected coils are 
positioned proximate a single low voltage coil, thereby magnetically flux 
coupling the coils to increase the transformer load capacity. 
U.S. Pat. No. 4,329,674 to Hamano teaches the combination of three 
transformers to form a single high voltage transformer, designed to 
provide a high DC voltage output. U.S. Pat. No. 1,907,633 to Westermann 
also teaches a means for the cascade connection of a series of 
transformers. 
A commonly utilized high voltage source is the Cockcroft-Walton type power 
supply. The Cockcroft-Walton supply utilizes series fed electrostatic 
coupled voltage multipliers which require large capacitance for coupling 
between stages. Alternatively, an Insulated Core Transformer (ICT) power 
supply can be utilized to provide the necessary high power requirements. 
However, ICTs require extremely large magnetic cores to reduce the effects 
of leakage flux between stages. 
SUMMARY OF THE INVENTION 
The present invention is a high power, high voltage source similar in 
construction to a transformer having a single primary winding and multiple 
secondary windings, spaced from the primary by an inert gas filled region. 
Principally, this invention provides apparatus to achieve a unique concept 
for a voltage converter, namely parallel excitation for either DC or AC 
employing a common primary core and multiple secondary cores connected in 
parallel. The device has a primary core and a separate secondary core for 
each of the secondary windings. The primary circuit supplies the necessary 
magnetomotive force to generate the magnetic flux necessary to feed the 
secondary coils across the gas gap between the cores. 
In direct current applications, the voltage from each of the secondary 
windings is independently rectified, and the DC voltages produced by the 
secondaries are connected in series. The total voltage generated by the 
power source is therefore determined as the sum of the voltages of each of 
the independent secondary circuits. 
The primary coil is preferably arranged in a cylindrical configuration, 
wherein the secondary coils are located within the cylinder and oriented 
transverse to the central axis thereof. The secondary is appropriately 
gapped from the primary and the intervening space filled with inert gas to 
prevent DC high voltage sparking. Each of the multiple secondary circuits 
employs a semi-cylindrically shaped magnetic core material for optimizing 
the flux coupling from the primary.

DETAILED DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS 
The present invention, as illustrated in FIGS. 1-4, is comprised of a 
primary magnetic core with two poles divided into two halves each half 
comprising one of two poles, 10 and 12. The two poles 10 and 12 of the 
primary core are fluxed-linked via vessel 14 or an additional laminated 
magnetic yoke positioned adjacent to but inside the vessel wall which 
provides a continuous magnetic flux path. A first half 16 and a second 
half 18 of a primary winding are wound about each pole 10 and 12, 
respectively and are connected in series via a lead 17. A separate 
secondary core is provided for each secondary winding. 
In FIGS. 1 and 2, three secondary coils and cores are illustrated for the 
sake of example. In FIG. 3, ten secondary cores and windings are 
illustrated for sake of example. The voltage generator of the present 
invention can have any number of secondary cores and windings as is 
necessary for the particular application of the device. The total voltage 
produced will be a function of the number of cores and independent 
windings as well as the number of turns of each winding. 
If each of the secondary windings are of equivalent voltage, the total 
voltage of the device having n number of secondary coils will be n times 
the voltage per coil. If the voltage of each secondary coil is different, 
the total voltage will be arrived at as a summation of the voltages of 
each secondary coil circuit. If a voltage multiplication circuit such as 
that illustrated in FIG. 2 is utilized in each or selected stages, the 
total voltage will be increased as the voltage of each circuit is 
increased. In the specific example of FIG. 2, a voltage doubler rectifier 
circuit is utilized to increase the voltage from each coil by a factor of 
two. 
The secondary circuits such as circuit 20 for example, are comprised of a 
secondary core element 22, a coil 24 wound about the secondary core 
element 22, and appropriate components to convert the AC voltage of the 
coil into a DC voltage. The conversion elements can be comprised of 
rectifiers such as 26 and 28 illustrated in FIG. 1, or 30 and 32 as 
illustrated in FIG. 2 combined, respectively with capacitor 29 or 
capacitors 36 and 38, as necessary. The output voltages of each secondary 
circuit are connected in series, one end 21 of the series being grounded 
and the opposite end utilized as the high voltage DC output potential 67. 
Either the positive or negative potential can be grounded depending upon 
the use of the power supply in either a positive or negative system, the 
opposite potential would then become the high voltage potential output. 
A common value for the input voltage V.sub.p is 480 Volts in the U.S. 
however, the voltage supplied to the present invention is variable to 
allow for producing variable values of DC output. The value of V.sub.p 
supplied to the present invention can be varied by any acceptable means 
such as a variable transformer between the line and the input of the 
present invention. Each secondary circuit or stage of the present 
invention can typically provide 10 to 100 Kilovolts (kV). These values are 
within the manageable range of voltages allowing for secondary insulation 
and not providing excess stored energy per stage. Therefore, to provide a 
typical 2 megavolts (MV) to an accelerator, between 20 and 200 stages 
would be necessary. The present invention accommodates as many or as few 
stages as needed or desired to provide adequate voltage for the intended 
application. 
The capacitance as illustrated for example by capacitor 29 in FIG. 1, is 
not strictly necessary for the production of the high voltage potential 
but may be required for filtering. The value of the capacitance needed is 
determined by the following formula: 
EQU C=100It.div.nV per phase per circuit, 
where: 
I=the DC average current in anperes 
n=the percent peak to peak ripple, 
v=the DC circuit voltage in volts 
t=time period from one rectification interval to the next in seconds and 
c=the capacitance in microfarads. 
Describing the apparatus illustrated in FIG. 1 in greater detail, there are 
three secondary circuits, 20, 40 and 60, illustrated. Again, any number of 
secondary circuits can be provided with each additional circuit readily 
connected in series with the existing circuits. A voltage V.sub.p is 
supplied across primary input terminals 70 and 72. Voltage V.sub.p is an 
alternating current source of sufficient magnitude to create the necessary 
magnetomotive force to supply the secondary circuits of the voltage 
generator. The voltage V.sub.p is supplied to the primary coil comprised 
of the two coil halves 16 and 18 each made up of a number of turns 
N.sub.p/2. The total number of turns for the primary coil being N.sub.p, 
i.e., the sum of the number of turns in each of the coil paths 16 and 18. 
The alternating current flowing through the primary coil creates a magnetic 
flux flow .PHI..sub.P as indicated by the arrow in FIG. 1. Some of this 
total magnetic flux flows in parallel through the secondary cores 22, 42 
and 62 in amounts .PHI..sub.S1z, .PHI..sub.S2 and .PHI..sub.S3, as 
illustrated by arrows in FIG. 1. For equivalent secondary circuits 20, 40 
and 60, .PHI..sub.S1, .PHI..sub.S2 and .PHI..sub.S3 should be equivalent 
also. The return path for the magnetic flux is through the vessel wall 14, 
or an internal magnetic yoke, as indicated by the arrows .PHI..sub.P/2 in 
FIGS. 1 and 3. 
The magnetic flux .PHI..sub.S in each of the cores 22, 42 and 62 creates an 
alternating voltage in each of the coils 24, 44 and 64 respectively. In a 
direct current application the voltage in each of these coils is then 
rectified to DC -nd connected in series as illustrated. The high DC 
voltage potential between 21 and 67, is thereby obtained through the 
parallel coupling of magnetic flux to each of the cores and the series 
cascade connection of the rectified output of each of the coils. 
As illustrated in the figures, the secondary cores and circuits are gapped 
from the primary core and circuit. This gap, 74, as best illustrated in 
FIG. 4, is filled with a high pressure insulating inert gas and provides 
the necessary DC insulation to prevent DC arcing and circuit breakdown. 
The secondary core 42, as illustrated in FIG. 4, is semi-cylindrical in 
cross-section in order that the outer surface will conform to the 
cylindrical shape of the primary core. The matching of shapes including 
shapes other than cylindrical allows for a uniform air gap. The air gap 74 
is designed as a minimum distance to maintain the leakage flux at a 
minimum but at the distance necessary to prevent sparking. 
The arrangement of secondary circuits illustrated in FIG. 2 allows for 
effective doubling of the DC voltage tapped from each secondary coil. 
As is conventional in voltage doublers, the secondary coils of FIG. 2 have 
two pairs of capacitors and diodes connected in series across each coil 
with the diodes oppositely poled to charge each capacitor to the full 
voltage across the coil during opposite phases. The capacitors are 
connected in series to the output load, thus doubling the output voltage. 
outer cylinder 76 and inner cylinder 78 are nonmagnetic, metallic cylinders 
which provide electrostatic shielding. Since high voltage appears between 
the two cylinders it is important to provide smooth continuous surfaces to 
prevent corona or DC voltage breakdown. 
The air gap 74 in conjunction with cylinders 76 and 78 and the size and 
diameter of each is determined by the maximum electrostatic field and the 
dielectric strength of the insulating medium to prevent voltage breakdown. 
Because the voltage generator of the present invention is parallel fed 
rather than series fed it provides for a much greater simplicity of design 
to achieve different energy or power levels. Higher voltage outputs are 
obtained simply by adding stages, increasing the gas gap spacing and/or 
changing the diameters of the secondary and primary circuits as well as 
through voltage multiplying methods. 
The adaptations of the structure of the present invention must conform with 
the maximum allowable voltage stress limits for concentric cylinder 
geometry. The current is increased through increasing the size of the 
magnetic circuits, rectifiers and/or filter capacitors as necessary. Also 
the voltage generator of the present invention can be optimized in overall 
size and weight through the increasing of the frequency of the operating 
current. This will allow for decrease in the size and weight of the 
magnetic materials and reduce the stored energy while increasing the 
energy output. There is, however, a tradeoff in increased eddy current and 
hysteresis losses through the increase in the operating frequency. These 
losses can be compensated for through utilization of superior core 
materials and construction techniques in order to maintain high power 
efficiencies. The improved construction techniques may include a magnetic 
yoke of laminated core material lining the vessel wall thereby 
substantially eliminated coupling of flux to the housing which is quite 
lousy due to its non-laminated construction and choice of material 
required for strength. 
FIGS. 5 and 6 illustrate an embodiment of the present invention configured 
for three phase power operation. The primary magnetic core is divided into 
three sections 80, 82 and 84 surrounded by the primary coil sections 90, 
92 and 94. Each secondary core is correspondingly divided into three 
sections 86, 87 and 88 with coils 96, 97 and 98, respectively. The three 
phase power generator is provided with a gas gap 81 and electrostatic 
shielding 83 and 85. Three rectifiers 91, 93 and 95 are provided for each 
secondary for conversion of the three phase output of each secondary to 
DC. Other forms of conversion can be utilized as desired; for example, a 
full wave, three phase bridge rectifier circuit employing six rectifiers 
per stage. 
As three phase power is provided to terminals 100 a magnetic flux is 
generated in primary core segments 80, 82 and 84, inducing flux in 
secondary cores 102, 104 and 106, generating current in secondary coils 
103, 105 and 107. The total output of the voltage generator is the sum of 
the rectified outputs of each of the secondary coils. 
Because many varying and different embodiments may be made within the scope 
of the inventive concept herein taught, and because many modifications may 
be made in the embodiments herein detailed in accordance with the 
descriptive requirements of the law, it is to be understood that the 
details herein are to be interpreted as illustrative and not in a limiting 
sense. 
Once given the above disclosure, many other features, modifications and 
improvements will become apparent to the skilled artisan. Such features, 
modifications and improvements are thus to be considered a part of this 
invention, the scope of which is to be determined by the following claims: