US1895231A - Constant current transformer - Google Patents

Description

Jan. 24, 1933. o. A. PEARSON ET AL CONSTANT CURRENT TRANSFORMER Filed Feb. 19, 1951 a. Lama AA INVENTdRS ATTORNEYS Patented 10.11.24, 1933.

or primary section of the transformer core UNITED STATES. PATENT orrrcs OSCAR A. PEARSON, OI OAK. PARK, AND CHESTER H. THORDARSON, OI CHICAGO,

ILLINOIS, ASSIGNOES TO THOEDABSON ELECTRIC MANUFACTURING COMPANY, OF

CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS CONSTANT CURRENT TRANSFORMER ap lication died February 19, 1931. Serial 110. 516,858

A further feature of the invention relates to the method of controlling the leakage characteristics of a transformer in accordance with the secondary load.

A further feature of the invention relates to a constant current transformer of the shell type having'a core which is easily assembled.

Another feature relates to the shell type of constant current transformer provided wlth magnetic shunts completely surrounded by the core, which shunts are integrally united to the core.

Another feature of the invention relates to a constantcurrent transformer employing a plurality of coil sections which aresym'xnetncally disposed about a common primary core and are rovidedwith magnetic shunts for maintaining the secondary current substantially constant, I

A still further feature relatesto the novel organization and arrangement of elements which go to make up a cheap, eficient and easily assembled constant current transformer wherein the magnetic efiects of the coil W1i1Cl ings are balanced.

In the single figure of the drawing, which shows a longitudinal section of the transformer, the numeral. 1 represents a pile-up of straight laminations constituting the main The numeral 2 represents a winding which surrounds the core portion 1, preferably at its center. Anysuitable design of coil winding may be utilized, In the case of constant current high duty transformers it is preferred to employ a so-called ribbon winding for this purpose. The winding 2 is of course insulated by a suitable insulating spool 3 from the core portion 1. It will he assumed for the present that the coil 2 constitutes the primary winding of the transformer, and if desired this coil may be provided with 'suit able taps. The secondary winding or windingsare represented in the drawing by the numerals 4 and 5 and are dis osed symmetrically about the core 1, pre erably at equal distances from the primary winding 2. The secondary windings 4 and 5 are insulated from the core 1 in any suitable manner, for example by being wound upon insulating spools 6.

For the purpose of completing the main ma netic circuit for the primary and secon ar windings there are provided two pileu s o laminations. The laminations of each 0 these latter sets comprises a portion 7 extending parallel to the main core portion 1, and end. or 1e portions 8 and 9 adapted to butt against the core portion 1, as shown in the drawing. Integrally formed with each of these laminations are two intermediate leg portions 10 and 11 which are slightly shorter than the leg portions 8 and 9, thus providing two gaps 12,- 13 on each side of the core portion 1. The legs 10 and 11 are preferably narrower than the legs 8 and 9 and serve as shunt paths for the secondary flux as is well known in the constant current transformer art. The ends of the legs 10 and 11 may be provided with notches 14 to receive clamping bolts or rivets for holding the shunt laminations rigidly together. The laminations of both the primary section 1 and the secondary or shaped sections are held together in any well known manner as by bolts or rivets 15, and if desired the entire assembly may be filled with tar, asphaltum or other insulating com-- pound for preventing vibration of the laminations, and the whole assembly may he enclosed in a suitable casing through which the bolts 15, if desired, may likewise pass to further clamp the laminations together. As will be obvious from the drawing the shunts 10 and 11 are positioned between the primary coil 2 and the associated secondary coils 4;.- and 5. Preferably the air gap 12 and the legs 10 and 11 are so designed that as the secondary load increases a corresponding increase in the shunting effect of the magnetic lines occurs through the legs 10 and 11' and.

across the said gaps. is not at all nece f;

ill)

sary that the secondary core portions 7 be saturated to achieve this re ulating efiect.

It will be obvious that t e reluctances of the shunt paths through the legs 10 and 11 may be chosen in any desired ratio with res act to the reluctance of the main magnetic ux path so as to provide the desiredregw lating action. Suitable insulating strips 16 are provided, for insulating the windings from the legs, 8, 9, 10 and 11 of the secondary portion of the core.

Inasmuch as the magnetic shunt legs 10 and 11 are integrally formed as part of the legs 7 it will be clear that the gaps 12 remain absolutely constant even though the laminations should be subjected to considerable vibration. Furthermore, the design of core as shown in the drawing enables the transformer to be easily and quickly assembled. Furthermore, once the length of the shunt legs 10 and 11 has been decided upon the shunt gaps 12 remain absolutely constant and no great care need be taken in assembling the core to insure the accuracy of these gaps since the gap is automatically determined by the len he of the legs 8 and 9 and the le 10 an 11. All that is necessary in assem ling the transformer is to position the windings upon the primary core portion 1, and then to assemble the secondary core portions with the legs 8, 9 abutting against the core portion 1, after which the entire assembly may be rigidl clamped together as a unit.

is a further advantage of the particular design of core shown, the reluctanceof the main magnetic path may be easily controlled merely by inserting suitable members between the ends of the legs 8, 9 and the core portion 1, although this latter feature is not absolutely necessary. The-action of the magnetic shuntsin shunting the main flux away from the secondary windings 4 and 5 increases as the secondary load current increases, as will be understood by those skilled in the art.

While certain specific arrangements and illustration of parts is shown in the drawing,

it will be understood that the invention is not limited thereto, and that various chan es and modifications may be made without eparting from the spirit and scope of the invention. Thus instead of positioning the primary winding 2 between the secondary, the primary winding may be made in two or more sections symmetrically disposed on the core section 1 with respect to the secondary winding which may take the place of the primary windin 2'as shown in the drawing.

Furthermore the dimensions ofthe respective sections of the core are shown in the drawing as merely illustrative and it will be obvious to those familiar with the art that the size of the core sections and the shunt sections will be chosen in accordance with the regulating characteristics desired. Furthermore, while the drawing shows a main or primary core section 1 and a plurality of secondary core sections disposed on opposite sides of the section 1, it will be understood that a single secondary core section may be employed.

Similarly in the arrangement actually shown in the drawing it is not abmlutely necessary to rovide gaps on opposite sides of the core 1. 'li hus the shunt legs 10 and 11 and half of the secondary core may be of the same length as the legs 8 and 9 while the shunt legs 10 and 11 of the other section of the secondary core may be shorter, as shown in the drawin thus providing only two gaps in lace oft e four gaps shown.

ther changes and modifications may be made without departing from the spirit and scope of the invention.

While in the foregoing description mention has been made of a primary winding and a pair of secondary windings, it will be understood that the secondary windings may be connected either in series or in multiple as desired, to constitute separate coil sections of the same winding, and similarly while the primary winding 2 is shown in the drawing as a single coil, it will be understood that this I winding may consist of two ormore coil sections connected in parallel or in series. In any event the arrangement of the coils or coil sections as shown in the drawing provides a symmetrical and properly balanced ma netic structure since the primary coil or coi s are symmetrically disposed with relation to the entire magnetic circuit, and also with relation to the secondary coils.

What is claimed is:

1. In a constant current transformer a core structure comprising a straight primary core portion, a secondary core portion having a pair of legs at opposite ends abuttin against said primary core portion, and a oreshortened leg intermediate the ends providing a gapped magnetic shunt between the primary and secondary core portions.

.2. In a constant current transformer, a core structure comprising a straight primary core portion, a secondary core portion having apair of legs at opposite ends abutting against said primary core portion, and a pair 0 foreshortened legs intermediate the ends providing a gapped magnetic shunt between the primary and secondary core portions.

3. In a constant current transformer a primary magnetic core, a central windin a pair of lateral windings spaced apart rom said central winding on said primary core, a secondary core for completely enveloping said coils, said secondary core having main magnetic lefis abutting said primary core an integra y intermediate shunt legs disposed between the central winding and the lateral windings.

4. A transformer comprising in combination a laminated core bar having at least two primary and secondary coils mounted thereon in end to end relation, a laminatedyoke member having at least one intermediate leg interposed between the ends of said coils with the end of said leg in close proximity to said first named bar but with an effective air gap between such parts and means for connecting the end le s of said yoke snugly in contact with said rst named oar.

5. A step-up transformer comprising in combination a laminated core'bar having a primary coil and two secondary coils mounted thereon in end to end relation with the rimary coil located between the two secon ary coils in spaced relation thereto, a laminated olre member having two intermediate legs interposed between the ends ofthe primary coil and the adjacent ends of the secondary coils, and means for connecting the end legs or said yoke snugly to said first named core bar.

6. A shell type of transformer compris-' snugly to said first named core bar.

7. In a transformer, the combination of a straight laminated core bar, a primary coil mounted on said core bar, a secondary coil mounted on said core bar in end to end re lation to said primary coil, a. second lanai-- nated core bar in spaced relation to said first named core bar and having at least one intermediate leg formed therewith extending between said coils into close proximity to said first rfamed core bar but with an efiective air gap between the 1e and said first named core bar, and an en leg at each end of the device each formed with one of said spaced core bars and extending into snug engage ment with the other one of said core bars.

8. In a transformer, the combination of a straight laminated core bar, a primary coil mounted on said core bar, a secondar coil mounted on said core bar in end to en relation to said primary coil, a laminated yoke member having an intermediate leg terminatin adjacent said core bar to form an air gap t erewith and lying between the adjacent ends of said coils and a leg at each end of said yoke and extending into snug engagement with said core bar. 7

9. In a transformer, the combination of av straight laminated core bar, a primary coil mounted on said core bar, two secondary coils mounted on said core bar, one on each side of said prima' coil and in end to end relation to said prlmary coil, a laminated yoke member having intermediate legs terminatin adjacent said core bar to form air gaps an lying between'the adjacent ends of the primary and secondary coils and a leg at each end of said yoke and extending into snug engagement with said core bar, ad acent the outer ends of said secondary coils.

In testimony whereof we have hereunto set our hands on this 14th day of February A. n, 1931.

- OSCAR A. PEARSON.

CHESTER H. THORDARSON.

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