US595403A - Transformer - Google Patents

Description

(N0 Modei.)

W. S. MOODY.

TRANSFORMER.

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UNITED STATES PATENT FFICE.

IVALTER S. MOODY, OF LYNN, MASSACHUSETTS, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, OF NEW" YORK.

TRANSFORMER.

SPECIFICATION forming part of Letters Patent No. 595,403, dated December 14:, 1897.

Application filed February 10, 1897. Serial No. 622,782. (No model.)

windings to a three-Wire circuit, as is now common practice, or, conversely, with transformers whose primaries are connected to a three-wire circuit and secondaries to a twowire circuit, or with transformers having both primaries and secondaries connected to three wire circuits. Three-wire transformers adapted for such service have heretofore been made with a rectangular core having only a single magnetic circuit with two primary coils co11- nected in series and arranged one on each leg of the core and two secondary coils also arranged one on each leg of the core. Ordinarily the primary and secondary coils are superimposed. Such a transformer gives eX- cellent regulation for varying loads so long as the load is maintained balanced on the different branches of the system and is for its regulating qualities and other reasons a very desirable form of construction. I have found, however,that when the secondary coils are arranged as described-that is, with the secondaries for the different sides of the system arranged each on its own leg of the core and adjacent to one of the primaries the regulation is unsatisfactory when the load becomes unequal 011 the different branches of the three wire circuit. While the load is equally divided, the counter electromotive force of each secondary maintains the proper relation to the electromotive force of the adjacent primary and the current in each secondary is practically due to the induction of the adjacent primary, the leakage of all the primaries and secondaries being a minimum. If now one side is heavily loaded and the other lightly loaded, the heavily-loaded secondary will take current not only from its adjacent primary, but from both primaries, and at the same time the normal relation between the counter electromotive force of the lightlyloaded secondary and the primary adjacent to it is disturbed, so that the leakage increases, due to the abnormal relation between the lightly-loaded secondary and the adjacent primary and the greater distance of the heavily-loaded secondary from said primary.

This increased leakage, I find, shunts the heavily-loaded secondary and decreases its voltage,while the leakage through the lightlyloaded secondary increases and its voltage rises. These of course are exactly the opposite of the conditions requisite for good regulation for unbalanced load in a three-wire circuit; To avoid this difficulty, I have subdivided the secondary coils heretofore employed and have distributed the coils feeding each branch of the three-wire circuit on the two legs of the transformer-core, so that the secondary winding connected to each side of the circuit receives induction equally from both of the primary coils. The total flux, therefore, will act equally on all the secondary windings. I find by test that in this way the difficulties in regulation heretofore existing on unbalanced load are overcome and that a transformer so constructed has excellent regulating properties not only for varying total loads, but also for unequally-distributed loads. In thus describing the transformer as having its secondaries connected to a three-wire circuit I have done so for convenience. As will be hereinafter pointed out, the invention may equally well be embodied by a like arrangement of the windings in cases where the primary coils are connected to a three-wire circuit and the secondaries to a two-Wire circuit, or where both primaries and secondaries are connected to three-wire circuits.

In the accompanying drawings, attached to and made a part of this specification, Figure 1 represents a two-wire system supplying the primary of a transformer the secondary of which is connected to a three-wire system. Fig. 2 represents a three-wire system supplying the primary of a transformer with the secondary connected to a two-wire system, and Fig. 3 is a detail of the mechanical construction.

bear to each other in practice.

In Fig. 1 the alternating-current generator A supplies current to a two-wire system by means of wires 13 and C. A single magneticcircuit transformer D is provided, consisting of a laminated core E, upon which are wound the primary and secondary coils. The primary coils F and F are mounted upon separate legs of the transformer-core and connected in series with each other and in shunt across the mains B and C. The secondary is divided into a number of coils G G G G. These coils are connected in pairs and the coils of each pair are mounted upon separate legs of the core E. Coils G G forming one pair, are coupled in series and connected between the main II and neutral wire I. Coils G G forming the second pair, are coupled in series and connected between the main J and neutral wire I. Coils G G, being mounted on separate legs of the transformer-core and at a substantially equal inductive distance from both the primary coils, will receive induction equally from both the primary coils. This is also true of coils G G which are connected to the other side of the system. By this arrangement each side of the three-wire system receives a substantially equal amount of current from both of the primary coils, and when the lights K, which form the load on one side of the secondary system, are cut out this influences practically alike the relation between the impressed and counter electromotive forces in each of the primary coils and the relation between the impressed and counter magnetomotive forces in each leg of the transformers, so that an unbalanced load does not give rise to an unbalanced inductive action between the primaries and secondaries and good regulation is secured.

In Fig. 2 is shown a three-wire system supplying current to a two-wire system by means of a transformer D. The alternating-current generator A supplies current to the three-wire system by means of a transformer T, to which are connected the mains a Z) and neutral wire 0. The primary coils of the transformer D are connected to the three-wire system by wires a b c. The transformer D is similar to the transformer D, (shown in Fig. 1,) except that the primary coils are now arranged and connected in a manner similar to the secondary coils in Fig. 2, and so also the secondary coils in Fig. 2 correspond in arrangement to the primary coils of Fig. 1.

WVhile I have shown the primary of transformer D subdivided and connected to a three-wire system and a secondary connected to a two-wire system, it is within the scope of my invention to connect both primary and secondary to a three-wire system and to sub divide them in the manner above described.

Fig. 3 shows the relation which the coils (For the purpose of illustration only one leg of the transformer is shown.) The core E is made of laminated iron and surrounding it is the primary coil F, which is suitably insulated therefrom. Superimposed on the primary coil F are the coils G and G These are suitably insulated from each other and the primary. If desired, the secondaries may be first applied to the core and then the primary.

It is preferable, if coil G is next to the primary F on one side, to place its companion coil G outside of the secondary G. By this means the coils of both sides will be subject to equal inductive effects.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. In a transformer, the combination of a core, a winding mounted thereon, and a winding in inductive relation to the first-named winding and connected to a three-wire circuit comprising a plurality of coils connected to each side of the three-wire circuit, said coils being so arranged on the core that they receive substantially equal induction from the first-mentioned winding under balanced and unbalanced loads.

2. The combination in a transformer of a core having a single magnetic circuit, a primary comprising a plurality of coils, each mounted upon a separate part of the core, a secondary subdivided into a number of coils and connected to a three-wire circuit, the coils which are connected to each side of the three-wire circuit being mounted 011 separate parts of the core, and receiving induction equally from all of the primary coils.

3. The combination in a transformer of a laminated core, primary coils mounted on separate parts of the core, a subdivided secondary set of coils connected to a three-wire circuit and superimposed upon the primary coils, the arrangement being such that the secondary coil which lies next the primary 011 one part is farther removed on the other.

The combination in a transformer of a laminated core having a single magnetic circuit, primary coils mounted 011 separate parts of the core and connected in series, a threewire secondary circuit, and a set of secondary coils for each branch of the three-wire circuit which are connected in series and are arranged on the core so that the coils connected across each of the different branches of the circuit are in substantially similar inductive relation to each of the primaries, as set forth.

5. .The combination in a transformer for three-wire circuits, of a core having a single closed magnetic circuit, primary coils arranged at different points on the core, secondary coils located on the core adjacent to the primary coils, and connections between the secondary coils and the three-wire circuit, such that a part of the secondary winding for each branch of the circuit lies adjacent to each of the primary coils, and the total sec ondary winding for each of the different branches of the circuit is in a substantially similar inductive relation to each of said primary coils.

6. The combination in a transformer, of a said pairs or sets of coils collectively considered are in substantially the same inductive 1o relation to the different primary coils.

In Witness whereof I have hereunto set my hand this 6th day of February, 1897.

WALTER S. MOODY.

WVitnesses:

B. B. HULL, A. F. .MAODONALD.

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