US669662A - Multiphase transformer. - Google Patents

Description

No. 669,662. Patented Mar. l2, I904.

v E. w. ms, in.

MULTIPHASE TRANSFORMER. (Application filed Dec. 14, 1898.)

(No Model.)

FTC-Ll- FAB.

m: Nonms PEYERS 00.. PHOTO-Lindon wAsHmumm u c UNITED STATES PATENT OFFICE.

EDWIN W. RICE, JR, OF SCHENEOTADY, NEW YORK, ASSIGNOR TO THE GENERAL ELEOTRIO COMPANY, OF NEW YORK.

MULTIPHASE TRANSFORMER.

.SYPEQLI' LCAIIQN forming part cf Letters Patent No. 669,662, dated March 12, 1901.

Application filed December l l, 1898. Serial No. 699,219. (No model.)

To all whom it may concern.-

Be it known that I, EDWIN W. RICE, Jr, a citizen of the United States, residing at Schenectady, in the county of Schenectady and State of New York, have invented certain new and useful Improvements in Multiphase Transformers, (Case No. 963,) of which the following is a specification.

My present invention relates to means for transforming three phase alternating currents, and has for its object to provide a transformer having a minimum number of primary and secondary windings, the same being arranged on a single core of such structure as to permit the use of a minimum am ount of iron.

My invention further relates to means for supplying currents of variable potential from the secondaries of multiphase transformers to induction-motors or other translating devices.

My invention Will be more clearly understood by reference to the following description and accompanying drawings, while its scope will be clearly and particularly pointed out in the accompanying claims.

Figure 1 illustrates in diagram a transforming device made in accordance with my invention, and Fig. 2 illustrates the use of the same for the purpose of supplying variable-potential three-phase currents to a translating device.

In transforming three-phase currents by the use of stationary induction apparatus it is a common practice to employ two separate transformers with their primaries connected across two sides, respectively, of the threephase system and with mains connected in a similar manner to the corresponding secondaries.

Instead of employing separate transformers in the manner described I have found that a considerable economy in iron may be secured by locating the primary and secondary coils on a single core of such a nature that the flux due to the action of one primary and its corresponding secondary may pass through a part of the iron core common to the magnetic circuit of the other primary and its secondary. The resultant flux passing through that part of the core common to both magnetic circuits is of necessity a resultant of two equal fluxes differing in phase from each other by an angle of one hundred and twenty degrees and is therefore equal in value to each of its component fluxes. The portion of the core carrying the resultant flux may therefore be the same in cross-section as those portions of the core carrying the individual fluxes, thus effecting a saving in iron over the arrangement employing separate transformers, but without increasing the core loss. Fig. l illustrates such an arrangement. The two primary coils which are to be connected across two sides of the three-phase system are indicated at 1 and 2. The corresponding secondary coils are shown at 3 and l. The limbs or branches of the magnetic circuit upon which the primaries and secondaries are wound are shown at 5 and 6. A third and unwound branch 9 serves a magnetic shunt or common magnetic return for the magnetic fluxes due to each set of transformer-windings and is the same in cross-section as those portions of the core indicated at 5 (5, while end pieces 7 8 are arranged to close the magnetic circuits of the three branches, as shown.

In Fig. 2 I have shown diagrammatically a transformer of the nature described in which the secondaries are tapped at intermediate points and the terminals led to a suitable controlling device, the function of which is to connect the terminals in a suitable manner to mains feeding a translating device or devices. The threephase supplymains are shown at a, b, and c. The transformer-primaries l and 2 are connected together at 10, and leads ll, 12, and 13 are connected, respectively, to the extremities and junction of said coils and supplied with three-phase currents from the mains a, b, and c. The corresponding secondary coils 3 4 are similarly connected together, with leads connected to their extremities, the junction of the two coils, and to an intermediate point or points in the individual coils. The leads are shown as connected to terminals 1% to 18 of a controlling-cylinder, (shown in a developed View.) In the first controller position the terminals 15 and 17, which are connected, respectively,

to the middle points of the secondary coils 4t and 3, and the terminal 16, connected to the junction of said coils, are by the action of said controller put in circuit with the three mains 19 20 21, which lead to the inducing member of the induction-motor M. The terminal 15 is connected through the contacts 22 and 23 of the controller with the main 19, the terminal 16 through the contact 24: with the main 20, and the terminal 17 through the contacts 25 and 26 with the main 21. In this position of the controller it will be seen that only a portion of tne electromotive force generated in the secondary coils 3 and 4.- is impressed on the motor M. The motor under these conditions is enabled to start without drawing from the mains an undesirably large current. As the motor speeds up the controller-cylinder is shifted to its second position, in which the conductors 27 and 28 are substituted for the conductors 22 28 25 26, the conductor 24 still remaining in connection with the terminals associated therewith in its first position. In this new position it will be evident from inspect-ion that the main terminals 14, 10, and 18 of the three-phase secondary coils 3 and e are connected directly to the supply-mains of the induction-motor M, thus impressing thereon the full electromotive force generated by said transformer.

Although I have shown but one intermediate connection for each secondary coil of the three-phase transformer, it is evident that any desired number may be employed without departing from my invention and that the leads connected to said coil may be manipulated through any suitable controlling device for putting them in connection with the workcircuit.

Iam aware thatithas been suggested to subdivide the secondaries of three-phase transformers; but in all prior arrangements of this sort with which I am acquainted the number of leads from the transformer-secondaries to the translating device have usually been equal to three times the number of working positions of the controller. Nith my improved arrangement, which is not necessarily restricted to use with the type of transformer shown in the drawings, I am enabled to reduce the number of leads without interfering with the action and to make the number of leads equal only to twice the number of working positions plus one.

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

1. The combination of a transformer having three legs of equal cross-section two of which are wound with primary and secondary coils while the third is unwound and means for-changing the ratio of transformation of said transformer.

2. The combination of a transformer having three legs of equal cross-section two of which are wound with primary and secondary coils while the third is unwound and means for varying the number of effective turns of said secondaries.

3. A transformer having three legs of equal cross-section, one of which is unwound while primary and secondary coils are placed on the other two.

4:. A transformer having a core which is traversed by three fluxes one of which is the resultant of two fluxes differing in phase by one hundred and twenty degrees.

5. A transformer having a core traversed by three equal magnetic fluxes one of which is the resultant of the other two.

6. A three-phase transformer having its secondary windings subdivided so as to obtain more than one ratio of transformation, the number of connections with the secondary windings being less than three times the nu mber of ratios of transformation obtainable.

7. A three-phase tranformer having its secondary windings subdivided so as to obtain more than one ratio of transformation, the number of connections with the secondary windings being equal to twice the number of ratios of transformation obtainable, plus one.

8. A three-phase transformer having two secondaries subdivided for obtaining a variable ratio of transformation and leads connected to said secondaries equal in number to twice the number of ratios of transformation obtainable, plus one.

In witness whereof I have hereunto set my hand this 12th day of December, 1898.

EDI/VIN IV. RICE, JR.

Witnesses:

B. B. HULL, M. II. EMERSON.

Images