US1873975A - Transformer - Google Patents

Description

Patented Aug. 30, 1932 PATENT OFFICE .AUGUST S, F BADEN, SWITZERLAND TRANSFOBIEB Application led November 5, 1929, Serial lo. 404,911, and in Germany November 80, 1928.

This invention relates to improvements in transformers and, particularly, to transformers required to o rate under cond1t1ons of heavy load and o vvariable voltage.

5 Electric locomotives require a transformer structure to receive the troll?7 li ne voltage and to supply voltage to the riving motors of the locomotives. The most usual and, certainly, the most .eilicient operation of 1o driving motors for electric locomotives requires wide voltage variations. Taps on the secondary winding of a transformer are 1mpractical because of the excessive current strength involved and taps on the rimary windlng of a transformer, by the ad 1t1on of a sufficient number of turns and the taps'necessar to obtain the proper wide range of regu ation are also im racticable because of the increased amount o space required therefore. The usual solution of this problem,

accordingly, is to provide an auto-transformer between the trolley line and the supply transformer for the motors of the locomotive.

This arrangement is, however, not advantageous because of the combined exiense and` weight of the auto-transformer an the supply transformer and the large amount of space rllxired for properly arranglng the same. e weight and space requirements are especially diiiicult to meet in. locomotive construction, for the reason that 1t 1s usually desirable to maintain the weight of the locomotive below a certain maximum and because the space available for the arrangement of apparatus within the locomotive structure limits is insuilicient.

It is, accordingly, among the objects of the present invention to provi e a unltary transformer structure capable of a wlde range of regulation for use 1n such circumstances as require a heavy load with a variable voltage between wide hmits.

Another object of the present invention is to provide a si le transformer structure which -will be lig ter and smaller than the auto-transformer and sup lyl transformer combination heretofore use for electric locomotives. 5 Objects and advantages, other than those above set forth, will be apparent from the following description and the drawing which diagrammatically illustrates an embodiment of the present invention.

Referring more particularly to the drawing u by characters of reference, l represents a 3- legged core having auto-transformer windin 4 arranged on one of the legs thereof; a primary wlnding 2 and a secondary winding'3 arranged on another (middle) leg of the core co 1, leaving one leg of the core unwound. The winding 4 is connected with the winding 2 in conductive, as well as inductive relation. The winding 4.-' is connected with the trolley line (not shown) and is provided with a plu- 6I rality of taps to form an auto-transformer connection to winding 2. The operation of the combined structure is such, therefore, that the connection of the supply current to the winding 4 produces, by means of the ta and 70 the conductive relation between windiiigs 2 and 4, a variable voltage in the winding 3 (which is closely coupled with winding 2). The connections are so made that the voltage supply to the secondary winding 3 may 75 be regulated within wide limits for the purpose of permitting production of the proper starting and operating conditions of voltage and current in the secondary winding 3 which is connected with the electric motors of an electric locomotive. Although not strictly necessary, it is desirable that the core l have an unwound leg to form a path for the magnetic flux set up in the core legs occupied by the auto-transformer winding 4 and the flux 95 caused by windin 2 and 3. The unwound core le according y forms a path for a magnetic ux which is the difference of the fluxes `in the wound core le It is, therefore, ad-

vantageous to so regu ate the number of turns ofthe several windings that the flux in the unwound leg is at a minimum.

The arrangement of all of the windings on a single core has the advantages that only a single core is required, which core is utilized 9 to its maximum so that the weight of a separate core for the auto-transformer is entirely eliminated, the expense of the combination is decreased by the cost of suchvcore. Another advantage of the present structure is lo that the core loss in the structure is less than the sum of the core losses would-be if separate cores were provided for both an autotransformer and a supply transformer. The structure, according to the present invention, therefore produces the same result that might be produced by the use of an auto-transformer and the usual separate supply transformer with a saving in weight of one core and the 1 corresponding saving in space required for' the two structures rather than for the unitary structure, according to the present invention.

Although but a single embodiment of this invention has been illustrated and described, it will be understood that various other -em`- bodiments are possible, and .that various changes may be made without departing from the spiritof the invention or the scope of the 2 appended claims.

The invention claimed is 1. A transformer comprising a core hav ing a central member and end members extending from one end of the central member to the other end thereof, an auto-transformer winding associated with said end members, and double wound primary and secondary windings onthe central member, the primary winding having a common line terminal connection with the auto-transformer winding at one end, and a variable tap connection therewith at the other end, whereby the said rimary winding may be energized under gull line potential or under a graduated series of 85 steps of less than full line potential.

2. A transformer comprising a closed magnetic circuit member, double wound primary and secondary windings on one part of said member and an auto-transformer winding provided with line terminals on another art thereof, one end of the said primary winding having a common line connection with a terminal of the auto-transformer, and the other end of the said primary winding having a variable tap connection alon the winding of the auto-transformer, wheriy the said primary winding may be energized by full line potential or by a graduated series of steps of less than full hne potential.

3. A transformer comprising a unitar magnetic circuit, an auto-transformer win ing provided with line terminals on one part of said magnetic circuit, and multiple circuit transformer windings on another part thereof, one of the said multiple circuit windings having one end connected to aline terminal and the other end connectiblc to variable volt-l age taps of said auto-transformer winding, whereby the said multiple circuit transformer winding ma be energized at full line potential, or any es ired lower potential.

In testimony whereof I have hereunto subscribed my name this 18th day of October,

YAUGUST MEYERHANS.

Images