US715930A - Transformer for polyphase alternating currents. - Google Patents

Description

Patented Dec. l6, I902.

no. namau.

E. ZlEHL. TRANSFORMER FOR POLYPHASE ALTERNATING GURRENTS.

(Application filed June 20, 1902.)

(No Model.)

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W/ TNESSES:

ATTORNEYS.

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UNTTE STATES EMIL ZIEHL, OF BERLIN, GERMANY, ASSIGNOR TO BERLINER MASGI-IINEN- BAU- AOTIEN- GESELLSOHAFT, VORM. L.

GERMANY.

SCI-IIVARTZKOPFF, OF BERLIN,

TRANSFORMER FOR POLYPHASE-ALTERNATING CURRENTS.

SPECIFICATION forming part of Letters Patent No. 715,930, dated December 16, 1902.

Application filed June 20, 1902. $erial No. 112,493. (No model.)

1'0 aZZ whom it may concern.-

Be it known that I, EMIL ZIEHL, engineer, a subject of the German Emperor, residing at Berlin, Germany, have invented certain new 5 and useful Improvements in Transformers for Polyphase Alternating Currents; and I do hereby declare that the following is a full, clear, and exact description.

The present invention relates to a method of construction of polyphase-current transformers in which the lines of force formed from the separate phases do not interfere with one another, inasmuch as intermediate connecting-bridges effect the equalization of i unsymmetrical loadings.

Hitherto it has been usual to employ two single-phase transformers for the conversion of two-phase alternate currents in stationary transformers. Polyphase-current tranform- 2o ers were usually used with three iron cores, which take up each a primary and a secondary phase of the polyphase current. Hitherto the currents which are displaced by 120 occasion, for the purpose of creating the neoessary electromotive force, magnetic fluxes in the iron cores, which fluxes periodically coincide or add themselves together in one or more cores,according to the chosen moment. Although this circumstance may appear advantageous at the first view, it is injurious, inasmuch as on the unequal loading of the separate cores these always influence the oth ers injuriously, and thereby occasion undesirable increases or decreases in the tension 5 of single phases. For the removal of these drawbacks for the primary windings the use of the triangular connection has been proposed; but by this means the advantages of the star connection for the primary winding are lost. The price of the transformers is not inconsiderably increased in consequence of the required production of an electromotive force greater by 1.73 times for each core, and in addition to this the object in View is still not fully attained. It is just becauseof these drawbacks that three monophase-current transformers have often been preferred to the polyphase-current transformers.

In order to remove in a reliable manner the injurious influence of one-sided loadings of the separate phases, a system of iron cores is adapted in the present invention in which the currents displaced in point of time induce the lines of force with such fluxes that they do not affect themselves within the windings or, in other words, in the so-called effective iron packets. This system of iron cores possesses intermediate bridge-pieces, which equalize the irregular loadings of single phases, so that the other phases are not thereby disturbed in their action.

The polyphase-current transformers constructed according to the present invention are illustrated diagrammatically in the accompanying drawings. In the drawings for the sake of clearness only the primary or only secondary windings, respectively, have been shown.

Figure 1 showsthe construction and mode of operation of a two-phase-current transformer. Figs. 2, 3, and 4 show a three-phasecurrent transformer also in construction and mode of operation. Figs. 5 and 6 illustrate another construction of the iron core for two and three phase current transformers.

In Figs. 1 to 4 the core systempossesses two longitudinal cores-a, two end bridges b, and one or more middle bridge or bridges c. The middle bridges c, in which the fluxes of the lines of force from vicinal windings or phases-sometimes add together and sometimes subtractenable, in combination with the outer bridges b, the equalization of onesided loads to be effected without the other phases being therebyinfluenced. Instead of 8 making the longitudinal cores so long that each of them suffices for all the various phases separate cores may also be used for each phase, and then the connecting-bridges may extend from one side to the other, or go' longitudinal cores with end bridges might be used, which pass from one side to the other.

The iron cores represented in-Figs. 5 and 6 consist of a plurality of horseshoe-shaped iron packets at of monophase-current transformers of the core type which are connected together into a single whole by means of a yoke-piece 6.

Having now described my invention and in what manner the same is to be performed,

what I claim as new, and desire to secure by Letters Patent, iso 1. In transformers for polyphase alternating currents, the combination of two longitudinal cores, end bridges and intermediate connection-bridges with coilsplaced on both longitudinal cores, the coils of each phase being placed opposite one another partly on the one and partly on the other longitudinal core,

10 substantially as shown and described.

2. In transformers for polyphase alternating currents the combination of several horseshoe-shaped iron packets d placed with their open and their closed ends side by side, the last open end being closed by a yoke-piece e, substantially as set forth and described.

In witness whereof I have hereunto set my hand in presence of two Witnesses.

EMIL ZIEHL.

Witnesses:

Dr. ZAHN, KARL HAHNLEIN,

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