US3177455A - Shell-type transformer core for ballast structure - Google Patents

Description

April 1965 E. scHwARz ETAL 3,177,455-

SHELL-TYPE TRANSFORMER CORE FOR BALLAST STRUCTURE Filed Aug. 8, 1961 3 Sheets-Sheet 1 20 I i agf T H MW WT T H 5 24 F266 II 14 W |I g k E 77x611 M H 1|! W. L /5 2 7 20 22 P321fl 4'0 Qhl f/ 1 I Z8 I H W i 1 g l'T I i 241 26 Wig 2T a0 1 1' 2g I F I k I l I" i "L 2? m MI m we UN: INVENTORS.

Q7701/vee y4 April 6, 1965 E. SCHWARZ ETAL 3,177,455

SHELL-TYPE TRANSFORMER CORE FOR BALLAST STRUCTURE Filed Aug. 8, 1961 3 Sheets-Sheet 3 I W. W .H WI i} .v I, IT! H I 2 IN VENTORS.

SZZZZUMQZQQZZ United States Patent 3,177,455 SHELL-TYPE TRANSFQRMER CGRE FQR BALLAST STRUCTURE Elias Schwarz and Julian Neiditch, Chicago, Ill., assignors to Advance Transformer Co, Chicago, Ill., a corporation of Illinois Filed Aug. 8, 1961, Saar. No. 130,170 6 Ciaims. (Cl. 336-465) This invention relates generally to ballast structures and more particularly is concerned with the construction of the core of a ballast intended primarily for series sequence ignition and operation of gaseous discharge lamps.

This invention comprises an improvement upon the structure of an application filed by the same applicants February 2, 1961 and bearing Serial Number 86,751 granted January 8, 1963, as Patent 3,072,826.

The construction of a ballast of the type described and claimed in US. Patent 2,558,293 requires an elongate electrical steel core normally made up of laminations of punched sheet steel stacked and assembled together. The basic core is known as a shell type structure in which there is a central winding leg on which the coils or windings are mounted side by side and there are two side legs spaced from the central winding leg and having yokes or bridging ends abutting the ends of the central winding leg and thereby providing a pair of parallel magnetic flux paths with the central winding leg providing the return common to both flux paths.

Generally the proportions of the core of these ballasts are such that the Width of the central winding leg is approximately twice the width of either of the side legs since it will be carrying approximately twice the flux.

In order to understand generally what is involved in a series sequence ballast of the type described and claimed in US. Patent 2,558,293 it may be said that this is basically a three winding ballast intended to ignite and operate a pair of gaseous discharge lamps. The lamps ignite seriatum and after ignition operate in series. There is aprimary winding, a first secondary winding 0r tickler, and a second secondary winding. The primary winding is mounted in the center of the core and the first secondary winding is mounted at one end of the core separated from the primary winding by a relatively large shunt in order that there be a very large amount of leakage reactance created during the operation or" the ballast. The second secondary winding is mounted on the other side of the primary winding opposite the first secondary winding, also at the end of the core and it is normally alongside of the primary winding sometimes separated by a shunt and sometimes abutting the primary Winding.

When the circuit is energized one lamp which is in series with a condenser and is connected either across the first secondary winding alone or across the primary and first secondary winding together Will ignite and current will flow through the condenser and first secondary winding, thereby causing a very substantial leakage reactance to come into effect. The secondary windings are arranged in bucking voltage relationship but when the large how of current occurs due to the ignition of the first lamp, there will be a phase reversal of the voltage in the secondary winding which will produce a voltage component to combine with the voltage of the second secondary winding and ignite the second lamp. Thereafter because of the high reactance of the first secondary winding, current will flow through the two lamps, the condenser and the second secondary winding in series, substantially bypassing the first secondary winding.

In the said Patent No. 2,558,293, the elongate iron core there shown was constructed of the so-called forced core variety in which the side legs and the end yokes are integral thereby providing a framing portion, and the central Winding leg is forced into the center of the framing portion, thereby providing windows so that windings which are mounted on the central Winding leg will fit between theside legs and the central winding leg.

More recently, however, the cores have been manufactured from so-called scrapless laminations as taught, for example, in US. Patent 2,892,249 and others. Such cores are punched from strips of electrical steel with mating projections and then are rearranged in such a manner that the necessary end yokes, shunts and so forth are formed from the projections and notches thereby effecting great savings in material.

The invention herein is concerned primarily with the construction of ballast which is formed of the so-called scrapless laminations.

The primary object of the invention is to provide ballast structure for use in a series sequence circuit in which the core of the transformer used in the ballast structure is formed of scrapless laminations of such configuration as to provide much more efiiciency of flux flow and minimum distortion during the operation of the apparatus.

Other objects of the invention are to provide a transformer core for a ballast structure which is intended to be incorporated into a series sequence circuit in which the dies required for stamping the laminations are simple, the structure is economical, the disadvantages normally attendant upon the manufacture of a transformer core of this type are obviated, and the resulting ballast is quiet, cool and efiicient.

Still a further object of the invention is to provide a structure in which the ends of the central Winding leg are both of substantially the same width so as to provide a rugged construction and more facile coil assembly.

Many other objects will occur as a description of preferred embodiments appear hereinafter and it will be seen that variations can be made without departing from the spirit and the scope of the invention.

In the drawings:

FIG. 1 illustrates the layout of nested laminations along a strip of steel moving horizontally through the punch press in which dies such as progressive dies are used to punch out the laminations.

FIG. 2 is a semi-diagrammatic sectional view taken through a transformer core constructed in accordance with the invention using the laminations which are stampedas shown in FIG. 1, with the laminations rearranged as will be described.

FIG. 3 is a circuit diagram of one form of ballasting circuit of a series sequence type.

FIG. 4 is a similar circuit diagram but showing a second form of series sequence ballasting circuit.

FIGS. 5, 6, 7 and 8 are semi-diagrammatic views, each of which shows in its upper portion a fragmentary sectional View through a transformer using scrapless laminations and in its lower portion the arrangement of the laminations nested together in the manner that they are disposed at the time they are repetitively punched from a continuous strip of steel.

Generally, the invention herein is concerned with a method of manufacture and a construction of an iron core ballast in which the core is made up of laminations of the scrapless variety punched from a continuous strip of metal with the central winding leg and the outer or side legs nested during the punching process. The laminations are then stacked and rearranged in such a man- Z her as to properly align the stacks to provide windows within which coils are disposed.

As mentioned previously, the primary characteristic of the structure described herein is that the ends of the central winding leg are the same width so that coils may readily be threaded upon the central winding leg. In the case of previous structures, the central Winding leg had a T-shaped configuration so that all of the coils or windings had to be threaded onto the central winding leg from one end.

By a novel arrangement which will be described in detail, the central winding 'leg of the core described in claims hereinafter is of such structure as to enable the coils tobe assembled from opposite ends thereof.

In FIG. 1 there is illustrated a strip of electrical sheet steel in the process of passing through a punching machine, for example, and having the nested lamination parts punched therefrom. The strip of sheet steel is designated generally by the reference character lid, and it will be seen that a set of laminations comprising generally two outer or side legs 12 and a central winding leg 14 are punched in nested condition. This is a repetitious pattern along the length of the steel strip lltl so that the total scrap which results is very small. The scrap is marked S and is cross-hatched in order to enable the same clearly to be seen.

A set of laminations for a core are shown to comprise generally elongatedE-shaped side legs 12 having lateral inward projections 16 and 18 at opposite ends thereof, with a third lateral projection 20 intermediate the ends thereof and a recess or notch 22 alongside the projection 20. The central winding leg 14'; has a width A which is very close to two times the width'B of the side legs in order to provide suitable flux carrying capacity. The projections 20, by virtue of the nesting of the lamination parts 12 and 14, will form cut-out notches 24 in the central winding leg, and the recess which is formed in the side leg between the end projection 16 and the intermediate projection 20 will comprise a. seat or window 27 whose purpose it is to accommodate one of the windings S of the ballast to be described.

The recess or notch 22 by virtue of its nesting arrangement with the central winding leg 14 will provide a pair of outward extensions 26 on opposite side edges of the central winding leg 14 adjacent the recesses 24. The length of the central winding leg 14' and the length of the side legs 12 are identical except that during the punching process, by virtue of the nesting arrangement, the central winding leg is oitset from the other two extending to the right as viewed in FIG. 1 beyond the lateral projections or extensions 18. The lateral extensions 18, therefore, notch into the central winding leg 14 and produce the recesses or notches 28 on opposite side edges.

The dimension of these notches 28 along the length of the central winding leg 1'4 which is identified as C obviously will be identical to the dimension Dof the lateral extensions l8.. It is unnecessary that thedimension E of the end formation which will be designated'St) be the same as the dimension D and, as a matter of fact, in order to prevent the dimension C from being excessively large, it will be found that the dimension E is normally larger than the dimension D.

Between the extension 20 and the extension18, the side members 12 will provide an elongate seat or notch designated 32 in which the windings P and S of the ballast to be described are adapted to be arranged.

are chosen of a suitable number of turns and size wires so that they will be accommodated in the windows27 and SZ. The side legs, now stacked in laminatiorn'are thereafter fitted upon the assembly comprising the central winding leg 14 and windings in the arrangement which is shown in FIG. 2 so that the inward extensions 2% are juxtaposed relative to the outward extensions 26, thereby forming a shunt designated as between the winding S and the winding P. Gaps of suitable dimension are provided at 355. It will be obvious that the total dimension across the resulting core, which core is designated generally 40 in FIG. 2, is equal to A plus two P where F is the lateral dimension of the extensions 16 and 18. The clamping notches 42 which are formed in each corner of the core may be disregarded. If we assign the letter G to the dimension from end to end of the extensions 26 and the letter H to the width of the side legs 12 at the extension 24, it will be obvious that the limitations on the dimension of G and ,H are controlled by the total dimension A plus two F. G plus two H must equal A plus two F with slight modification to take care of the width of the gaps 38. The depth of the notch 22 will equal one-half of G minus A. Likewise the depth K of the notch 24 is equal to H minus B.

Since the dimensions J and K are related, one can work out the necessary dimension F to accommodate a suitable width of winding which will give satisfactory dimensions I and K for a given structure.

With respect to the notch 28, it has been found that this is desirable since it appears beneath the winding S which is intended to carry the leading current. Wave shape is thereby improved and saturation in the core is decreased. 7

Reference may be had to FIGS. 3 and 4 which illustrate the circuits in which the ballast of the type shown in FIG. 2 are intended to be used. As noted, each of these circuits usesa primary winding P, a first secondary winding S and a second secondary winding S In each case the windings S and S are normally bucking on open circuit while the winding P is additive to the winding S in FIG. 4 and bucking S in FIG. 3. Line voltage is applied across the Winding P in each case, thereby generating a voltage in the winding S which by itself, in the case of FIG. 3, and together with the voltage of P in FIG. 4 is sufilcient to ignite the fluorescent lamp L in thetwo circuits. As 'soon as current flows in the lamp L and through the condenser'C, there is a phase reversal in the winding S in each case so that there is a component of voltage which is opposite to that shown by the arrows ofthe figures. In the case of FIG. 3,.tl1e voltages of P and S now combine with the component of S which is in phaserwith the voltages. of P and S and in the caseof FIG. 4, the volt-age of S combines'with the.

component of S; which has now changed its phase so that there is sufficient voltage to ignite the lamp L In The above structures are explained in more detail in 7 US. Patent 2,558,293 and the various requirements for the core of such ballasts are met in the structure of FIG.

. 2. It is required that theprirnary winding P be located Informing the core of the ballast, assuming that the S in that order, are slipped over the right-hand end .7

and moved along the central winding leg 14 until the winding P engages against the projections 26 and the winding S abuts against the winding P. The windings in the center of the core. and separated from the other twowindings which are arranged on opposite sides thereof. Winding S is separated from winding P by a substantial magnetic shunt 36, and the winding S is loosely coupled with the winding I either by a shunt or by mere side by side placement.

' The structure which has been described is advantageous in that the core is readily formed with a minimum of scrap and is easily assembled. In the remaining figuresof the drawings, composites are shown in order best to illustrate the manner inwhich the modified forms are punched as well as assembled.

In each case, below the center line the core structure is,

shown in nested condition exactly as it would be punched from a moving strip of steel passing through a punch press. In the portions of the figures above the center line, the core structures are shown arranged at the time they are assembled in stack formation and provided with windings in order to provide the necessary ballast core structures for use with circuits of the type shown, for

sion 53% formed in the central winding leg 514. This structure differs from that of FIGS. 1 and 2 in the respect that it is desired that there be an additional small shunt 556 between the windings P and S and hence, the outer legs 512' are provided with inwardly extending extension 552 which because of nesting with the central winding leg 514 will give rise to the notches 554 that appear beneath the winding S As previously explained, this is advantageous in that the winding S is intended to carry a leading current and the presence of a reduced section will improve the wave shape. In the structure of FIG. 5, during the punching of the laminations, the central winding leg is nested to the left of the side portion 512 so that the lateral extensions 51% engage in the body of the central Winding leg 514 and thus provide the formation 530 at the left-hand end substantially equivalent to the formation 3GB of FIGS. 1 and 2 at the right-hand end. This means that there will be a much larger notch 528 beneath the winding 8,, and because of the need for the shunt 536, cooperation between the extension 538 and the lateral extension 52%) will produce an additional notch 522 in the side legs 512 outside of the winding 8,. An additional notch 521 will be formed beneath the primary winding P which will not have any deleterious effect. Note that agian the width of the lateral extension 516 as indicated at D is less than the Width of the formation 530 as indicated at E.

FIG. 6 is a figure which is arranged similar to that of FIG. 5 illustrating a ballast core 64-0 formed in a manner not much different than the ballast 540. The only significant difference is that instead of a shun-t 550, Windings P and S are abutted, and in order to provide the necessary decrease in the amount of iron beneath the winding S in order to improve wave shape, a slot 654 is punched in the central winding leg 6M. respects, the similarity is obvious.

FIGS. 7 and 8 are arranged similar to FIGS. 5 and 6 except in each case the winding S is shown at the righthand end instead of the left. The cores 7% and 84% are substantially longer, and in each case there is a shunt 75% and 85% formed between the windings S and P in the same manner as in the case of the core 540 in FIG. 4. These two figures illustrate the manner in which dimensions may be varied and adjusted to meet certain requirements and conditions. Note, for example, that the right-hand end of theside legs 712 has the lateral extensions 718 much narrower than the opposite end lateral extensions 716. This gives rise to a notch 72% beneath the winding 8 which is much smaller than the notch 528 of FIG. 5 and 828 of FIG. 8.

It is believed that no further explanation is necessary, and it is pointed out that the structure and method of the invention herein is simple and efiicient.

What it is desired to secure by Letters Patent in the United States is:

1. A transformer core of the shell type for a ballast structure mounting a multiple winding electro-magnetic device, said core comprising, three parts of substantially In all other identical length cooperatively assembled together to form the shell, each part formed of individual electrical steel laminations stacked and arranged together to provide a central winding leg and a pair of like side legs on opposite sides of and parallel to the winding leg to form the side parts of the shell, inner edges of the side legs having a configuration which is a nested configuration of the opposite sides edges of the central winding leg, each side eg being of elongated generally E-shaped configuration, the winding leg having opposite ends of substantially identical width, the side legs having projections extending laterally inwardly from opposite ends thereof into abutting engagement with said opposite ends of the wind ing leg to form the bridging end parts of theshell, said winding leg and side legs having respective cooperating lateral extensions intermediate the ends thereof facing one toward the other to divide the interior of the shell into a pair of windows for windings to be supported on the central winding leg and to form at least one shunt on the core.

2. A transformer core as described in claim 1 in which said side legs each has a recess in an edge thereof corresponding in linear dimensions to the linear dimensions of the lateral extensions on the winding leg and the central winding leg has recesses in opposite edges thereof corresponding in dimensions to the lateral extensions on the side legs.

3. A tranfsormer core as described in claim 2 in which said recesses are located on opposite sides of and immediately adjacent said shunt.

4. A transformer core of the shell type for a ballast structure mounting a multiple winding electro-rnagnet device comprising, three parts of substantially identical length cooperatively assembled together to form the shell, each part formed of like electrical steel laminations stacked and arranged together to provide a central winding leg and a pair of like side legs on opposite sides of and parallel to the winding leg to form the side parts of the shell, the side legs each having an inner edge the configuration of which is a nested configuration of the opposite side edge of the central leg, each side leg being of elongated generally E-shaped configuration, the winding leg having opposite ends of substantially identical width, the side legs having projections of equal width extending laterally inwardly from opposite ends thereof into abutting engagement with said opposite ends of the winding leg to form the bridging end parts of the shell, said Winding leg and side legs having respective lateral extensions intermediate the ends thereof facing one toward the other to divide the interior of the shell into a pair of windows for windings to be supported-on the central winding leg and'to form at least one shunt on the core, said central winding leg having recesses in opposite edges thereof the dimensions of which are identical to the dimensions of said projections and opening into only one of said windows.

5. A transformer core of the shell type for a ballast structure mounting a multiple winding electro-rnagnetic device comprising, three parts of substantially identical length cooperatively assembled together to form the shell, each part formed of like electrical steel laminations stacked and arranged together to provide a central winding leg and a pair of like side legs on opposite sides of and parallel to the winding leg to form the side parts of the shell, the side legs each having an inner longitudinal edge the configuration of which is a nested configuration of the opposite longitudinal edge of the central leg, each side leg being of elongated generally E-shaped configuration, the winding leg having opposite ends of substantially identical width, the side legs having projections extending laterally inwardly from opposite ends thereof into abutting engagement with said opposite ends of the winding leg to form the bridging end parts of the shell, said winding leg and side legs having respective lateral extensions intermediate the ends thereof facing one toward the 3 other to divide the interior of the shell into a pair of windows for windingsto be supported on the central winding leg and to form at least one shunt on the core,

the linear width across the lateral extensions of said winding leg and twice the width of a side leg at the lateral extension thereof being approximately equal to device comprising three parts of substantially identical length cooperatively assembled together to form the shell,

'shapedconfiguration, the Winding leg having opposite ends of substantially identical width, the side legs having projections extending laterally inwardly from opposite ends thereof into abutting engagement with said opposite ends of the winding leg to form the bridging end parts of the shell, said winding leg and side legs having respective lateral extensions intermediate the ends thereof facing one toward the other to divide the interior of the shell into a pair of windows of different dimension considered along the length of the core for windings to be supported on theoentral winding leg and to form at least one shunt on the core, each of said windows arranged to have a winding supported therein intimately engaged against said facing extension ends.

References Cited in the file of this patent UNITED STATES PATENTS 2,509,188 Feinberg May 23, 1950 2,510,209 Bridges June 6, 1950 2,671,951 Sliwiak Mar. 16, 1954 2,734,176 Gould et a1. Feb. 7, 1956 2,892,249 Feinberg et al. June 30, 1959 2,958,931 Hurt Nov. 8, 1960 3,003,081 Huberty et a1 Oct. 3, 1961 3,010,050 Hume et a1 Nov. 21, 1961 3,010,185 Hume Nov. 28, 1961 Feinberg 'Aug. 21, 1962

Claims (1)

1. A TRANSFORMER CORE OF THE SHELL TYPE FOR A BALLAST STRUCTURE MOUNTING A MULTIPLE WINDING ELECTRO-MAGNETIC DEVICE, SAID CORE COMPRISING, THREE PARTS OF SUBSTANTIALLY IDENTICAL LENGTH COOPERATIVELY ASSEMBLED TOGETHER TO FORM THE SHELL, EACH PART FORMED OF INDIVIDUAL ELECTRICAL STEEL LAMINATIONS STACKED AND ARRANGED TOGETHER TO PROVIDE A CENTRAL WINDING LEG AND A PAIR OF LIKE SIDE LEGS ON OPPOSITE SIDES OF AND PARALLEL TO THE WINDING LEG TO FORM THE SIDE PARTS OF THE SHELL, INNER EDGES OF THE SIDE LEGS HAVING A CONFIGURATION WHICH IS A NESTED CONFIGURATION OF THE OPPOSITE SIDES EDGES OF THE CENTRAL WINDING LEG, EACH SIDE LEG BEING OF ELONGATED GENERALLY E-SHAPED CONFIGURATION, THE WINDING LEG HAVING OPPOSITE ENDS OF SUBSTANTIALLY IDENTICAL WIDTH, THE SIDE LEGS HAVING PROJECTIONS EXTENDING LATERALLY INWARDLY FROM OPPOSITE ENDS THEREOF INTO ABUTTING ENGAGEMENT WITH SAID OPPOSITE ENDS OF THE WINDING LEG TO FORM THE BRIDGING END PARTS OF THE SHELL, SAID WINDING LEG AND SIDE LEGS HAVING RESPECTIVE COOPERATING LATERAL EXTENSIONS INTERMEDIATE THE ENDS THEREOF FACING ONE TOWARD THE OTHER TO DIVIDE THE INTERIOR OF THE SHELL INTO A PAIR OF WINDOWS FOR WINDINGS TO BE SUPPORTED ON THE CENTRAL WINDING LEG AND TO FORM AT LEAST ONE SHUNT ON THE CORE.

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