US2782358A - Power supply - Google Patents

Description

Feb. 19, 1957 'J. KOZlNSKl POWER SUPPLY 2 Sheets-Sheet 1 Filed March 19, 1953 IN hm H2 H 1 I: Q w MW NEW M v N 1 ain Feb. 19, 1957 J. KOZINSKI 2,732,358

POWER SUPPLY Filed March 19, 1953 2 Sheets-Shet 2.

INVENTOR. fir

4 J M C (ea/0 United States Patent 6 2,782,358 POWER SUPPLY Joseph Kozinski,.Chicago, lll.,,assignor toH; G. Fischer & Co-, F.r:anldin-Park, Cook County, 111., a corporation of Illinois Application March 19, 1953, Serial No. 343,461-

Claims. (Cl. 321 --16) This invention relates to a power supply for loads requiring extremely high potentials, but drawing little currentl While the power supply, embodying the present invention; may have a wide variety of uses, it is particularly well adapted for electrostatic paint spraying systems and" other systems requiring similar loads. In such systems, high potentials of the order of 100,000 and even more volts are necessary. The current drain is very low, usually of the order of several milliamps. To maintain desirable operating conditions, it is necessary that the potential on the electrodes of the load be maintained at substantially desired value for load conditions. On the other hand, the extremely high potential involved renders such a system hazardous unless means are'provided for removing the danger of electrocution.

customarily, such power supply systems have poor systemshaving a lowcurrent drain under normal loadconditions, that conventional construction technique-results in seriousoperational disturbances. Thus for example, any-moisture or dirt forming a surface leakage path between twoparts at high potential will generallyconduct enoughcurrent at the high potential used to affect seriouslytheoperation of the system.

In accordance with this invention, I provide a mechanical. insulatorv construction having longleakage paths thereby minimizing the effects of" any leakage current forming a load upon the system. Because of -'the weight of the various elements, and for mechanical reasons, the

frame-work of the power supply is preferably constructed of steel. Thevarious parts, such as transformers, are rigidly securedto this frame-Work. Other parts, such as tube sockets, are secured upon insulators carried by the frame-work. The insulating members supporting the high potential parts of the power supply are constructed in such a fashion as to provide long surface leakage paths. oil, which is usually used'as a medium for-surrounding the power supply, may be utilized.

In addition, a high potential power supply used for paint sprayers and X-ray equipment is generally provided with highpotential sockets. Such sockets provide a detachable connection for plug connectors so that high potentialleads may be readily coupled to the power supply. As arule, such sockets-are generally-tubular and-have a closed bottom. It hasbeen foundthat un- Consequently, the full insulating value of the- 2. desirable insulation. is provided in such sockets; Thus moisture may provide leakage paths to ground. In accordance with this invention, I provide apertures in thesocket, said apertures communicating with the interior of the casing containing the power supply. The oil used in such casing for insulating purposes may, therefore, flow into the high potential detachable sockets. The high potential plug connector may readily establish connection to the high potential socket connector even in the. presence of the oill However, the oil will provide a film or layer of material having a high insulating value around the plug of the cable.

In addition to a transformer having poor regulation for supplying high potential, I have found that poor regulation may be greatly enhanced by providing a special. type of transformer for supplying current to the transformer having poor regulation. Thus I have found that remarkable results are obtained by cascading two transformers, both having poor regulation under operating conditions. In particular I have found that at least one ofthe transformers should preferably be of the constant voltage type operated. at or near an overload point where further overload results in a precipitous drop in output potential.

Conventional transformers having poor regulation usually have high leakage reactance obtained by non-magnetic gaps or having a part of the core operated at high flux density. So-called'constant potential transformers are designed so that for a predetermined load, the output potential wilfremain substantially constant over substantial variations of input'or supply potential. Such transformers however have a steep voltage drop at overload and may be operated near a' desired overload point so'that the output potential will drop sharply for any additional overload. An example ofa constant potential transformer system having the above characteristic is the voltage stabilizer sold-by Raytheon Mfg. Co. and made under United States Patents 1,985,634 and 5. Transformers of the constant potential type having similar overload characteristics are made and sold by others.

In order thatthe invention may be understood, it will now be-explained'in connection with the drawing, wherein anexemplary embodiment is illustrated. It is understood, however; that substantial variations in construction may be -madewithoutdeparting from the spirit of.

the invention,- except-as defined by the appended "claims.

Figure l is a perspective elevation of'a power supply em'bodyingthe present'invention, the tank and i oil'b'eing omitted;

Figure-2 is arr-elevation, from-aidifferent side; of the power supply of Figure-1;

Figure-.3 'isacircuit diagramofa power supply system" embodying the: invention;

Figure 4 -is a perspective view' of one slotted'insulator support;

Figurefiis a top viewof the-transformer forsupplyi'ng the highpotential of the system;

Figure'6'is a-perspectiVevie'w of another high potential any suitable source of alternating current, as a-conv'en tional Gil -cycle 1l0 volt supply' line. Transformer system 10 is of the type designed to provide a substantiallycon stant out-put potential fora certain load'in spite of-substantial variations-of input-potential. The characteristics of this havet-been previously set forth. Th'e'outputpo tential oftransformer System10 may have *any: desired value.

The power supply systern which'is housed as a unit is generally indicated by :12. and includeshighpotential step up transformer 14 having primary 15 and secondary 16, this transformer having power regulation. Primary 15 has a number of taps 17, with which switch pointer 18 cooperates to select one tap for connection thereto. The reason for providing primary taps is to insure that transformer system 10 may be properly loaded over normal load so that any additional load on system 10 will result in a sharp drop in output potential. Thus transformer system 10 operates at an unstable overload point.

Secondary 16 is connected by wires to terminals 28 and 21 of a bridge rectifier system. The rectifier system has rectifiers 22 to inclusive. The rectifiers are preferably of the high vacuum electron discharge type available in the market and designed for such devices as X-ray tubes and similar apparatus. The rectifier tubes are connected as shown, in conventional bridge relation and have output terminals 27 and 28.

The rectifiers have cathodes which are either directly or indirectly heated and in any event require heating current for the same. The cathodes for rectifiers 22 and 23 will be at the same potential so that a common filament winding for these two rectifiers may be used. The cathodes for rectifiers 24 and 25 will require separate filament transformers, suitably insulated from each other and from the output terminals of the bridge system.

Connected across the input terminals for transformer primary 15 are supply wires and 31. These supply wires energize primaries 32 and 33 of transformers 35 and 36. These transformers have secondaries 42, 44 and 45. Secondary 42 is connected to energize the cathodes for rectifiers 22 and 23. These two cathodes may have their heaters connected either in series or in parallel, as desired. Secondary 44 is connected to supply the heating current for rectifier 24 while secondary 45 is connected to energize the cathode for rectifier 25.

Referring now to the remaining figures, the physical construction of the portion of the power supply generally indicated by 12 is illustrated.

The power supply as a whole involves transformers which have substantial weight and therefore require strong support. To this end, a steel angle iron construction, as indicated by numeral 50, is provided. This consists of four vertical angle irons 51 to 54 inclusive, supported and made rigid by angle iron rectangles generally indicated by numerals 55 and 56 at the top and bottom respectively. Across the top system of angle irons 56 insulating panel 57 is supported, this panel being made either of glass, Bakelite, Lucite or other material having desired insulating characteristics, resistant to oil and also having desired mechanical properties.

Hook-eyes 58 are firmly attached at the corners of the entire steel skeleton so that the same may be elevated or lowered, as may be necessary. The entire power supply is supported within this steel frame-work in a manner to be described, and the frame-work and power supply are disposed in tank 60 of steel or insulating material, as desired, this tank being filled with transformer oil. The rim of panel 57 forms a cover for the tank.

Supported near the bottom of the steel frame-work is transformer 35 having the usual laminated iron core and provided with primary and secondary windings. This transformer has its secondary winding insulated from the primary and from the grounded core. The secondary insulation is suflicient so that if terminal 27 is to be at high potential, rather than ground, the transformer secondary may function effectively. Either terminal 27 or 28 may be grounded or both may be insulated from ground.

Transformer 35 supports insulating member 66 carrying rectifier tube connectors 67 and 68. Two rectifiers (only one tube happens to be shown in Figure 1) are provided, the rectifiers having conventional bases 70, with prongs for cooperating with spring connectors. The rectifiers include elongated glass envelopes and have external anode terminal leads, the anode lead for rectifier 22 being indicated by numeral 71. Each external lead terminal comprises a metal cap at the end of the envelope and is in common use. The rectifier tubes extend across the steel frame-work and the anode terminals engage spring clips 74 and 75. These clips are usually of copper and are available for insuring firm contact with the anode terminal.

It will be evident that the full difference of potential developed by high potential secondary 16 will be impressed across anode terminals 74 and 75. It is of the utmost importance to insure against variable resistance leakage paths, either between these two terminals or between either or both terminals and the steel frame-work. To this end, an insulating support, shown in perspective in Figure 6, is provided. This insulating support consists of material such as Bakelite, formica, hard rubber or any other solid insulating material. This material, generally indicated by numeral 77, has high potential supporting portions '78 and 79 at the opposite ends of insulator body portion 88. Body portion 80 consists of an elongated strip of insulating material having suitable thickness for mechanical support and provided with mounting portions 81 and 82. These mounting portions are suitably apertured at 83 and are so dimensioned as to extend between supports 85 and 86 rigidly secured to angle irons 51 and 52. Supports 85 and 86 are of insulation.

Supporting portions 81 and 82 of insulating body portion 80 taper down to reduced body portions 88 and 89. Body portions 88 and 89 are separated from terminal supporting portions 78 and 79 by slots 90 and 91. These slots extend longitudinally of strip 80 and define the lower edge of supporting portions 78 and '79 and extend inwardly past the metal high potential terminal clips. The length of slots 90 and 91 may vary within wide limits, but, in general, these slots should be long enough so that any path from either high potential terminal clip, such as 75 for example, to the nearest mounting end 81, will be substantially longer than the shortest distance between these two parts. Thus it is clear that any leakage path along the body of insulating material 80 will extend around the slot and thus be lengthened. The supporting ends of the insulator strip will be close to a metal tank wall so that leakage along the support ends of the insulator may be a serious problem.

Disposed above rectifiers 22 and 23, and the corresponding transformer, are angle irons 93 and 94 upon which is bolted transformer 14. This transformer is shown in Figure 5 and consists of laminations 95 upon which are disposed primary windings 15a and 15b on opposite legs of the transformer core. These windings may be connected either in series or parallel, depending upon their design and, as shown in Figure 5, are oflfset from each other with respect to the transformer window. Insulation material 96 and 97 is disposed upon the opposite legs of the transformer core, such insulation material consisting of paper or varnished cloth or other suitable material having high insulating value and capable of withstanding immersion in oil.

Disposed on insulation 96 and 97 are the primary windings, previously referred to, and also secondary windings 16a and 16b.

By insulating both the primary and secondary windings of high potential transformer 14, core 95 may be maintained at ground and may be bolted to the angle irons in any suitable manner as shown, for example, in Figure l.

Disposed above transformer 14 is additional transformer 36, whose iron core stack is rigidly bolted to a skeleton frame. Secondaries 44 and 45 are disposed at the two ends of a core leg while primary 33 is disposed under the secondaries. High potential insulation including spools are provided. Transformer secondary 44 may be disposed close to secondary winding 1612 while secondary 45 may be disposed in proximity to secondary 16a. The connections are so arranged that the only difference in potential between secondary 44, for example, and the high potential terminal of secondary 16b will be due to the drop through the corresponding rectifier tube in the bridge system. Since the drop is usually low, in comparison to the potentials handled, it will be seen that the insulation problem is greatly simplified.

Secondary 45 is correspondingly near to secondary 16a and in this particular instance, the potential difference may be above one-half of the entire potential developed in the system.

Above these filament transformers is insulating strip 103 supported on insulating arms 101 and 102. These arms itll and 102 are rigidly bolted to angle irons 53 and 54. insulating strip 1% contains a pair of rectifier tube sockets or connections of construction similar to that used on insulating strip as. Insulating strip 100 is so designed that the leakage path between the cathode and filament connections, both at high potentials, and steel parts will be quite long. These insulating strips have slots 1% and 104 at each end. The slots extend from opposite sides of the insulator and are so arranged that a long, tortuous leakage path is provided in a manner similar to that shown in Figure 6.

Rectifiers 24 and 25, similar to rectifiers 22 and 23, are provided. These rectifiers extend across the steel skeleton frame-work generally parallel and above rectitiers 22 and 23. Rectifiers 24 and 25 have external anode terminals connected to spring clips held by insulating strip lit suitably supported in the steel frame-work. This construction is identical with the construction described previously in connection with the anode terminals of rectifiers 22 and 23, so that any further description is not necessary.

in order to establish detachable external connections to a load, panel 5'7 carries high potential jacks 112 and 113, suitably connected to the proper portions of the power supply system. These jacks consist of insulating tubes having internal metal terminal 114. The jacks themselves consist of hollow tubes having open ends disposed above panel 5'7. Into these open ends there may he slipped suitable plug connectors.

To provide adequate insulation Within the jack chamber, it is preferred to have insulating tubes 112 and 113 apertured so that oil Within casing 60 may rise in the jack tubes. It has been found that oil in the jack tubes provides excellent insulation and minimize leakage along the surface of the insulating material of which the tubes are formed. The tops of the tubes are usually bolted to the panel and the hardware is grounded.

Heretofore, it has been the practice to have the jack tubes sealed as far as access from the interior of the casing to the interior of the jack tube is concerned. Thus in such prior devices, the jack has had no oil. Moisture in the tube or along the plug tends to provide low resistance leakage paths. Such leakage paths to the grounded metal parts at the top of the jack increase hazards and also load the system.

The mechanical construction so far described has the electrical parts connected in the manner illustrated in Figure 3. It is understood that these connectors are established in such a manner as to provide against short circuits. The power supply so far described has been found to have such a high insulation resistance that substantial percentage variations of this resistance have negligible effect upon the current drain of the power supply.

What is claimed is:

1. In a high voltage, low current type of power supply, the combination of a pair of cascaded iron core transformer systems having high leakage reactance, one system having a primary for connection to an alternating current power line, the other system having a secondary output for delivering high potential, said one transformer system being of the type having a substantially constant output potential for a predetermined current load over variations of primary input potentials, said one transformer system beyond a predetermined current overload having sharply reduced output potential, said other transformer system having high leakage reactance for providing poor voltage regulation with increase in load current, means for operating said one transformer system at said predetermined point, as a normal part of the operation of the two systems whereby upon overload of the second transformer system, the output potential of the second transformer system will drop faster and further than would normally be the case with only one or the other of the transformer systems alone.

2. The system according to claim 1 wherein means are provided for supporting portions of said power supply system, said means including solid insulator supports having slots provided for increasing the surface distance between points on the insulator having high potential differences therebetween.

3. In a high voltage, low current type of power supply, the combination of a transformer system providing a high potential output, said transformer system having poor voltage regulation so that the voltage drops when the current increases, a steel frame-Work for supporting the various parts of said power supply, a tank containing transformer oil into which said steel framework and power supply are disposed and means including slotted insulating strips for supporting portions of the power supply normally at high potential, said slots being so oriented and extending for a suficient distance so that any leakage path between a portion of the insulating strips at high potential and a portion of the insulating strips near the steel frame-work is substantially longer than the straight-line distance therebetween.

4. The system according to claim 3 wherein at least one electron discharge vacuum tube type of rectifier is connected to the output of the transformer system, and wherein said rectifier is supported at least at one end of said slotted insulator.

5. In a high voltage, low current type of power supply, the combination of a tank having an insulating cover, said tank containing a power supply and normally having the interior filled with an insulating liquid such as transformer oil, at least one socket carried by said cover and extending inwardly into the tank, said socket cooperating with an external plug for providing a detachable elec-trical connection to an outside circuit, said socket having at least one aperture through the wall for permitting a flow of insulating liquid to the interior of the socket from the interior of the tank, whereby high potential insulation inside of the socket is provided.

References Cited in the file of this patent UNITED STATES PATENTS

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