No. 687,042. Patented Nov. [9, I901.

A. D. LUNT.

ANTIHUNTING DEVICE.

(Application filed June 25, 1900.

(No Model.)

Witnesses: Jnventor. Alexander I). Lunt,

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UNITED STATES PATENT OEEIcE.

ALEXANDER D. LUNT, OF SCIIENECTADY, NEIV YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ANTIHUNTING DEVICE.

SPECIFICATION forming part of Letters Patent No. 687,042, dated November 19, 1901.

Application filed June 25, 1900. Serial No. 21,420. (No model.)

To all whom it may concern.-

Be it known that I, ALEXANDER D. LUNT, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Antihunting Devices, (Case No. 1,351,) of which the following is a specification.

My present invention relates to a means for preventing hunting of synchronous alternating-current machines-such, for example, as alternating-current generators, rotary converters, or the like.

Specifically considered, my invention coinprises short-circuited conductors placed about the pole-tips of the machine to which the device is applied. These short circuits since they embrace only the pole-tips of the machine are consequently very compact in structure, and being of minimum length or extent are therefore of minimum resistance, thereby giving rise to correspondingly powerful currents which oppose any hunting tendency which may exist.

The details of my invention, as well as its mode of application,will better be understood by reference to the following description and the accompanying drawing.

The points of novelty of the invention will be set forth in the claims appended hereto.

The drawing represents a synchronous alternating-current machine having an'armature indicated merely by the circle 1 and a field-magnet structure or frame 2. In the particular case shown the machine is provided with four poles similarly constructed, the structure of one of which is shown in detail at 3. This latter pole-piece is shown partly in section and partly in side elevation. The field-Winding is indicated at 4: and is held in place between the heads 5 6 of the fieldspool. The pole-piece itself is provided with tips 7 8, extending oppositely from the pole and located in close relation to the surface of the armature 1. The ends of the tips 7 and 8 are, however, slightly chamfered off, as indicated at 9 and 10, respectively. An oblong mass of metal having an elongated opening therein is slipped over each pole-tip. These masses of metal form the seats of induced currents, the reaction of which opposes any hunting tendency of the machine. The form of cross-section of these antihunting devices is represented at 11 and 14, the lower limb 11 of the device being wedge-shaped, so as to fit under the chamfer 9 of the pole-tip 7 and lie in as close proximity as possible to the surface of the armature 1. The lower limb is somewhat extended along the surface of the armature, so as to form a projecting tip, as shown. The lower and upper limbs of the sections of the device are connected by integral end connections indicated in the draw-- ings at 12. To secure the antihunting device in place any suitable mechanical device may be employed--such, for example, as set screws 13, engaging slight depressions in the surface of the pole-tip.

In operation powerful currents are set up in the short circuits described, the path of the currents being, as will readily be seen, along the lower limb or limbs 11, through the end connections, and then across the top limb or limbs 14.. The currents thus set up act powerfully to oppose irregular motions of the armature to which the existence of these currents is due. Owing to the exceedingly compact nature of the short-circuit devices the currents induced therein are exceedingly powerful and act eifectively to prevent hunting without at the same time giving rise to an undue expenditure or waste of energy.

WVhat I claim as new, and desire to secure by Letters Patent of the United States, is-- 1. An antihunting means for synchronous alternating current dynamo electric ma chines comprising a mass of metal surrounding a pole-tip of the machine to which it is applied.

2. An antihunting means for synchronous alternating current dynamo electric machines comprising a mass of highly-conducting metal surrounding a pole-tip of the machine to which itis applied.

3. An antihunting device consisting of an 5 elongated band adapted to embrace a pole tip or pole-corner of a dynamo-electric machine.

4:. An antihunting device consisting of a band of lrighly conductive material adapted IOO provided With pole-tips, and closed circuitconductors embracing said pole-tips.

8. The combination of a synchronous a1- ternating-current dynamo-electric machine provided with pole-pieces, and separate closed circuit-conductors embracing tips of said pole-pieces.

In witness whereof I have hereunto set my hand this 25d day of June, 1900.

ALEXANDER D. LUNT.

YVitnesses:

BENJAMIN B. HULL, MABEL I-I. EMERSON.