US2935548A

US2935548A - Electrical apparatus

Info

Publication number: US2935548A
Application number: US606092A
Authority: US
Inventors: Kozinski Joseph
Original assignee: HG Fischer and Co Inc
Current assignee: HG Fischer and Co Inc
Priority date: 1956-08-24
Filing date: 1956-08-24
Publication date: 1960-05-03
Anticipated expiration: 1977-05-03

Description

May 3, 1960 J. KOZINSKI ELECTRICAL APPARATUS 2 Sheets-Sheet Filed Aug. 24, 1956 INVENTOR.

0a EN? Mk May 3, 1960 J. KOZINSKI ELECTRICAL APPARATUS 2 Sheets-Sheet 2 Filed Aui. 24, 1956 United States Patent ELECTRICAL APPARATUS Joseph Ko zinski, Chicago, Ill., assignor to H. G. Fisher & Co., Cook County, 111., a corporation of Illinois Application August 24, 1956, Serial No. 606,092

2 Claims. (Cl. 174-17) This invention relates to an electrical apparatus and more particularly to a supporting structure for the high potential parts of a power supply for loads requiring extremely high potential but drawing little current.

Power supplies for X-ray systems or electrostatic paint spraying systems as an example provide extremely high potentials of the order of 100,000 volts or more and currents which are very low, in the order of one ormore milliamperes. 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. Systems of this character having high potentials may be hazardous unless means are provided for protecting a person against danger of electrocution. Thisis particularly true in power supply units where electrodes at high potential are exposed and are readily accessible. In order to provide such protection, it is customary to have the power supply for such systems so designed that any current drain in excess of normal load, results in a sharp drop of the output potential. Thus poor regulation is required for removing the hazard of electrocution.

A power supply for X-ray or electrostatic paint spraying systems as a rule is constructed to form a compact unit and is generally designed to operate within a casing which may or may not be sealed, as conditions warrant. Such a power supply generally includes such devices as transformers having high step up ratios, vacuum tube rectifiers, tube sockets and wiring between parts as well as physical support or supports for the various components making up the power supply.

It has been found that in a high voltage, low current power supply system, conventional construction and the use of certain materials may result in serious disturbances during operation. Thus power supplies of the type referred to are generally immersed in oil or other liquid normally having a high insulating value. So long as the moisture content of the liquid insulator is kept at an extremely low value, many solid insulators when immersed in oil may function satisfactorily. However oil will usually contain more than a trace of moisture and such moisture may be absorbed by certain portions of the system, particularly certain types of insulators with a resulting decrease in insulator value.

In particular, I have found that an oil immersed high potential low current type of power supply should have insulator supports for various components constructed to provide not only long leakage paths but also to have little or no moisture absorption characteristics. In accordance with this invention, I provided an insulator construction for an oil immersed high potential low current power supply, such insulating construction not only havinglong leakage paths but also having extremely low moisture absorption characteristics.

In my prior application Serial No. 343,461, filed March 16, 1953, now Patent No. 2,782,358, issued February 19, 1957, Idisclose an insulator construction wherein the insulator itself may be made of Bakelite or other suitable plastic material. In the practical use of the invention Patented May 3, 1960 ICC disclosed in my previous application referred to above,

- the insulating strip of Bakelite may have substantial length, such as of the order of from six inches to over a foot and may have a Width of several inches. For mechanical reasons, the thickness of such insulators will generally be at least inch, depending upon various other factors. It is difiicult and extremely expensive to use pure Bakelite resin to fabricate such insulators and in fact it is impossible for the average customer to mold the material out of pure Bakelite resin because of the com paratively long lengths of material. The so-called Bakelite sheets which are available for use in the manufacture of such devices as long insulating bars are not of pure resin but resin with filler, such as paper, cellulose, wood or the like. If Bakelite sheets are immersed in oil and no means are taken to maintain a very low moisture content in the oil surrounding the power supply, there is a tendency for the moisture to be absorbed in the Bakelite insulator and impair the insulating value thereof. In accordance with this invention, I provide high potential insulators having long leakage paths and free of filler materials like paper or wood which have substantial moisture absorption tendencies. In particular, I prefer to use material such as Glastic or Mycalex for high potential insulator use where oil immersion for the insulator is provided. The

, material known as Glastic consists of a phenolic resin with a filler of spun glass. This material is available in the market under a variety of names, one of which is Glastic.

The material known as Mycalex is a combination of powdered mica and glass and has desirable mechanical and electrical properties. However, Glastic is preferred for the reason that it is cheaper in price and functions as well.

In addition to the above non-absorption type of insulators, I use Bakelite or similar insulators having moisture absorption properties The Bakelite insulator however, is not used for high potential insulation and is used because it is strong, cheap and will absorb moisture.

In order that the invention may be understood it will now be explained in connection with the drawings wherein an exemplary embodiment is-illustrated. It is understood however, that substantial variations may be made without departing from the spirit of the invention except as defined by the appended claims.

Referring to the drawings,

Figure 1 is a front elevation of a power supply embodying the present invention.

Figure 2 is a side elevation of the power supply of Figure 1.

Figure 3 is a top plan view of one form of high potential insulator structure used in the power supply of Fig ure 1.

Figures 4 and 5 are respectively front and side views of the construction illustrated in Figure 3.

Figures 6, 7 and 8 are corresponding views of a modified insulating structure.

The electrical portion of the system need not be described indetail and is the same as is disclosed in my prior application previously identified. It is enough to state that the power supply has various parts at high differences of potential, which parts must be insulated from each other and from ground.

The power supply as a whole includes transformers which have substantial weight and require strong supports. For this'purpose, a steel angle iron construction as indicated by numeral 10 is provided. This consists of four vertical angle irons 11 to 14 inclusive supported and made rigid by angle irons 15 and 16 around the top and bottom of the frame respectively. Across the group of top angle irons is supported insulator cover 17. Cover 17 is preferably made of glass or Lucite or Qlastic,

all resistant to oil and also having minimum moisture absorption and having suitable mechanical properties. Hook eyes 18 are firmly attached at the corners of the steel skeleton construction so that the same may be elevated or lowered as required. The power supply is supported within this steel framework and the framework and power supply are disposed within tank 20 of steel or insulating material, as desired. Tank 20 will be filled with transformer oil.

Supported near the bottom of the steel framework is transformer having a laminated iron core and provided with primary and secondary windings. This transformer has secondary windings 42 insulated from the primary windings and also from the grounded cores. Transformer 35 supports insulating member 46 carrying rectifier tube connectors 47 and 48. The power supply is adapted to accommodate four rectifiers, the rectifiers having conventional bases with prongs for cooperating with spring connectors. Each rectifier includes a rigid glass envelope and has leads at the'two ends of the envelope. Each anode terminal lead is in the form of a metal cap at the end of the envelope. The tubes are adapted to extend across the steel framework, there being two at the bottom and two at the top. The anode terminals of the bottom two engage spring clips 54 and 55 of spring copper.

The full difference of potential developed by the transformer is generally impressed across anode terminals 54 and 55. It is therefore of the utmost importance to have clips 54 and 55 supported by means having a long leakage path and also having substantially negligible moisture absorption characteristics.

Spring clips 54 and 55 are rigidly secured to elongated strip 57 of Glastic. Strip 57 is supported at central portion 58 by bolts 60 of insulating material, such as nylon. The nylon used is of the hard variety. Bolts 60 pass through countersunk apertures in strip 57 and engage threaded recesses in insulating sleeves 62. Insulating sleeve 62 in preferably of Lucite although it can be of glass or Glastic, Mycalex or the like.

Two insulating sleeves 62 are attached to insulating bracket or bar 65 which is directly bolted to the steel framework. The attachment between insulating sleeve 62 and bar 65 may be by bolts 66 which may be of nylon. Bolts 6% and 66 are alined within each insulating sleeve 62, the opposite ends of the bolts however, having ample separation between the same. Bar 65 may be of such material as Bakelite, impregnated with cotton, wood fiber or other cellulose material in which the sheet Bakelite is usually available in the trade.

Instead of using nylon as the material for the bolts it is possible to use Mycalex or other insulating material having good machining properties. By having strip 56 sufficiently long and thus providing a long leakage path, it is possible to use conventional Bakelite as the material for the bolts and also for the supporting sleeve 62. However, best results are obtained by using the material specified.

Disposed above the level where the bottom two rectifiers are supported are angle irons 16 upon which is bolted transformer 67. This transformer consists of laminations 68 upon which are disposed two primary windings 6? and 70 on opposite legs of the transformer core. The two primary windings may be connected in series or in parallel and are offset from each other with respect to the transformer window looking down upon the core. The transformer window itself is generally rectangular and-the ofiset of the windings is to permit adequate insulation and clearance between the various windings without requiring an excessively large transformer window.

Disposed over the primary windings are secondary windings 71 and 72. It is understood that adequate insula-.

tion is provided between the primaryand secondary windings. Thus, for example, such insulation may consist of sheet rubber or plastic such as Lucite having high insulating value and capable of withstanding immersion in hot oil. It is preferred to insulate both the primary and secondary windings of the high potential transformer so that the core of this transformer may be grounded and may be bolted to the angle irons directly rather than on insulators. Y

Disposed above transformer 67 is filament transformer '76 whose iron core structure is rigidly bolted tothe steel skeleton frame. The iron core has one leg extending within the space enclosed by the skeleton construction. Over this leg is disposed primary winding 78. This winding requires no high potential insulation from the core since the potentials in primary 7a; are relatively low. Thus the primary is usually energized from a 110 or 220 volt alternating current line.

The transformer has secondaries 84 and 35 which supply currents for the filaments of the two rectifiers supported at the top of the power supply. These Secondaries must be insulated above ground for the full difference of potentials across secondary windings 84 and 85. As disclosed in my prior application, secondaries S4 and 85 are disposed in spaced relation to the primaries. Secondaries 84 an 555 are supported by conducting arms 161 to 104 inclusive, the arms extending back toward the core of the transformer.

Above this filament transformer is insulating strip 100 preferably of Glastic. Insulating strip 100 is generally similar to insulating strip 57 previously described except that the strip carries at each end conducting support arms 1G1 to MP4 inclusive. Support arms 101 to 102 form one pair and are adapted to support secondary 84 and carry heating current for one rectifier tube. Arms Hi3 and 304 form another pair of support members for secondary and carry heating current for the other rectifier tube. These arms carry blocks at the ends thereof for clamping the windings which they support.

Strip 1% is supported from insulating bar 110 in generally the same fashion that strip 57 is supported on insulating bar 65. Insulating bar also carries some terminals 112 to engage the proper pins in the tube bases.

The power supply disclosed herein may be connected in a number of ways. As a rule, the power supply will have the four rectifiers arranged as a full wave system. With such an arrangement, two terminals on one of the Glastic bars, 57 and 1%, will have the full rectifier potential between them. The two terminals on the remaining Giastic bar may be at or near ground potential. Thus it is possible to have only'one of the bars, 57 or 100, of Glastic or other material having substantially no moisture absorption characteristics. It'is desirable to have both bars of Glastic so that the user may use any desired hook-up.

It will be clear that any one bar, 57 or 100, having the two ends supporting terminals at opposite potential, will have the center portion thereof at neutral potential, which may be substantially equivalent to ground. For example, if top bar 100 has the two terminals at extreme potentials, the center bar portion will be at neutral potential (the difference in potential is alternating in character). It is possible to support bar 104) from the center portion directly from the steel framework with no insulation. In other words, the nylon bolts and/ or sleeves and/or Bakelite bar may be replaced by metal. However the arrangement disclosed is preferredto provide a high safety factor. It is understood that in all cases, the Glastic bars are long enough so that good insulation, both along the bar surface and within the bar material is afforded under operating conditions.

What is claimed is:

1. A high potential power supply for anX-ray tube or an electrostatic paint spray system, said. power supply being adapted to provide normally an output current of the order of about, 1v milliampere .at a high, potential of the order of about 100,000 volts, said power supply having poor voltage regulation with the output potential dropping rapidly as the current drain on the power supply goes above its normal rated value of about 1 milliampere, said power supply comprising a grounded metal framework supporting such components as transformers, rectifiers and the like, said power supply including as a part thereof a housing filled with an insulating liquid such as transformer oil within which the power supply components are immersed during normal operation, said insulating liquid normally having some trace of moisture therein as an impurity, said power supply including two terminals within said insulating liquid and between which there are normally high differences of output potential, and a supporting structure for supporting said high potential terminals from said grounded metal framework within said liquid, said supporting structure comprising one elongated member extending between the two high potential terminals with each terminal supported at an end of said elongated member so that substantially the full length of said elongated member is between the high potential terminals, said elongated member being of rigid insulation having high potential electrical resistance characteristics and being free of tendency to absorb moisture within the interior thereof, said one elongated member providing a long surface leakage path between the high potential terminals, said supporting structure including additional insulating means rigidly attached to the center part of said one elongated member and constituting the sole means of support for said elongated member, and means for supporting said additional insulating means at two spaced regions on said groundedframework, said insulating structure as a whole providing for leakage paths from each high potential terminal to ground of one-half the length of said elongated insulating member plus the added distance on the additional insulating means whereby moisture present in the insulating liquid cannot affect the current drain of the output of the power supply so that the output potential of the power supply will be determined solely by the normal load.

2. The construction according to claim 1 wherein said additional supporting means includes a generally T-shaped portion with the bottom of the T joined to the center part of the one elongated member and the ends of the top of the T being attached to the grounded frame.

References Cited in the file of this patent UNITED STATES PATENTS 1,088,197 Aichele Feb. 24, 1914 2,208,232 Smolak July 16, 1940 2,377,355 Mueller June 5, 1945 2,782,358 Kozinski Feb. 19, 1957 OTHER REFERENCES Properties of Teflon, Du Pont Product Engineering Bulletin 52, 1954.

Mycalex, Engineers Handbook and Catalog, 1952.