US865985A - Variable-voltage transformer. - Google Patents

Description

No. 865,985. PATENTED SEPT. 17, 1907. T. M. BAINS, Jn.

VARIABLE VOLTAGE TRANSPORMER.

" APPLIoATIox FILED 223.13.1907.

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Inventor;

0V Thomas Mai Jr: y Oqtty UNITED- STATES l1 rrrriivi onnron.

THOMAS M. BAINS, JR., OF PHILADELPHIA, PENNSYLVANIA, ASSIGNORl TO GENERAL ELEOTRICCOMPANY, A CORPORATION OF NEW YORK.

VARIABLE-VOLTAGE TRANSFORMER.

Specification of Letters Patent.

Patented Sept. 17, 1907.

Application filed February 8, 1907. Serial No. 356,478.

To all whom 'it may concern:

Be it known that I, THoMAs M. BAINS, Jr., a citizen of the United States, residing at Philadelphia, county of Philadelphia, State of Pennsylvania, have invented certain new and useful Improvements in Variable-VoL tage Transformers, of which the following is a specification.

My invention relates to variable-voltage transformers oi the type in which the primary flux is shifted into and out of inductive relation to the secondary'winding, so as to vary the induced'secondary voltage.

The object of my invention is to provide a novel construction for, such transformers, which is compact and of high efiiciency.

In carrying out my invention, I arrange the core with three legs and mount the primary coil on one leg with the secondary coil surrounding both the leg on which, the primary coil is placed, and also a second leg. And I provide a movable. magnetic member for shifting the primary flux from one to the other of the other two legs.

Or, expressed in another way, I arrange the secondary coil outside ofthe primary coil with an inside diameter substantially greater than the outer diameter of the primary coil, and shift the primary-flux from a return-path within the secondary coil to' a return -path outside of it. When the flux returns through the secondary coil, it induces no voltage in it, but when it returns outside the secondary coil, the primary flux is interlinked with the secondary coilin the usual manner.

My invention further comprises employing an auxiliary secondary coil, so arranged as to oppose the induced secondary voltage, due to leakage, in the position of minimum voltage, so as to securea resultant secondary voltage of aero. This coil is so arranged as to be of practically no effect when the induced secondary voltage is at'its maximum. 'Y

My invention will best be understood byl reference to the accompanying drawings, in which v Figure l shows a side elevation in cross-section of a variable voltage transformer arranged in accordance withniy invention; Fig. 2 shows a. plan view of the same; Fig. 3 shows the core and coilsdiagrammatically; and Fig. 4 shows a modification.

In the drawings, A represents d magnetic core, which has three parallel legs al, a2, and a, On thel central leg a2 is mounted the primary coil B.

(l is thesecondary coil, which surrounds' both the primary coil `B and the lleg h1. The secondary coil thus has an inside diameter substantially greater than the outer diameter of the primary coili- Drepresents a movable magnetic member which is supported from and slides on the' rods E; being moved nearly closed magnetic circuit with the legs a1 and a2, so that the primary flux in the leg a2 finds a return path through the leg a1. This return path is inside the secondary coil, and-induces no voltage in the secondary coil, so that this position of the member D corresponds to minimum secondary voltage. When the member D is moved into the position shown in dotted lines in Fig. 3, a nearly closed magnetic circuit is formed with the legs a2 and a3. The primary flux now returns outside the secondary coil (l, and is consequently linked with this coil in thc usual manner. The dotted line position of member D is consequently the position oi maximum induced secondary voltage. At intermediate positions the induced voltage will have intermediate value.

If it were not for leakage, the induced secondary voltage would be zero, with the arrangement of windings shown in Fig. 3. when the member D is in its full-line position. A certain portieri of the primary flux, however, will leak across .to the leg ai. and consequently return outside of the secondary coil. This leakage iiux is interlinked with the secondary coil and induces a certain voltage therein. In order that the minimum value of the secondary voltage may be zero, l make useof the auxiliary secondary winding c, shown in Fig. 4. I place this winding on the leg a1 and connect it in opposition to the main secondary winding C. When the vmember D is in the position oi minimum induced secondary voltage, which is the dotted-line position in Fig. 4, the greater part of the primary flux is linked with the auxiliary Winding c and induces therein a voltage which neutralizes the voltage induced in the main secondary winding C by the leakage flux, so that the resultant secondary voltage is zero. When the member D is in the full-line position in Fig. 4, in which the indliced secondary voltage is maximum, the auxiliary secondary winding c is threaded only by a small leakage flux, and consequently has a practically negligible effect.

` l I do not desire to limit myself to the particular construction and arrangement of parts here shown, but aim in the appended claims to cover all modifications' which are within the scope of my invention.

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

1. In a variable voltage transformer, a three-legged core, a primary winding surrounding one leg, a secondary winding surrounding both the leg carrying the primary winding and a second leg, and means for directing the iiux from the leg carrying the primary winding through the otherv two legs alternately.

2. In a variable voltage transformer, a three-legged core, a primary winding sux-rounding one leg, a secondary winding surrounding both the leg carrying the primary winding and a second leg, und means forgradually shifting the return ilux of the primary winding from one to' the other vo1! the other two legs.

3. In a variable voltage transformer, a three-legged 'leg carrying the primary winding' and either of the other legs.

4. in a variable voltage transformer, a primary coil, a secondary coll surrounding the primary and having an inside diametersubstantially greater than the outside diameter of the primary coil, and means for causing;r the flux passing through the primary coil to return either inside or outside the secondary coil.

5. In a variable voltage transformer, a primary coil, a secondary coil surrounding the primary and having an inside diameter-substautially greater than the outside diameter of the primary coil, and a movable magnetic member adapted `aradually to shift the flux passing through the primary coil from a return path inside the secondary coil to a return path outside it.

(i. ln a variable voltage transformer, a three-legged core, a primary Winding.: surrounding one leg. u main secondary winding surrounding b oth the leg carrying the adapted gradually to shift the tiux passing through the v primary coil from a return path inside'the main secondary coil lto a return path outside it, and an auxiliary secondary coil inl inductive relation to the return path within the mainsecondary coil and connected in opposition to the main secondary coil. V

in witness whereof, I have hereunto set my hand this 25th day of January, 1907. 'rrioMAs M. BAINS, .nu

Witnesses: 4

L. T. MmrwiN, BEN Nonni.

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