US400680A - Daniel higham - Google Patents

Description

(No Model.)

D. HIGHAM.

PREVENTION OF SPARKING IN EEEGTEIG- MOTORS AND GENERATORS.

No. 400,680. Patented Apr. 2. 1889.

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PREVENTION OF SPARKING IN ELECTRIC MOTORS AND GENERATORS.

SPECIFICATION forming part of Letters Patent No. 400,680, dated April 2, 1889.

Application filed March 5, 1887. Serial No. 229,778. (No model.)

To all whom it may concern.-

Be it known that I, DANIEL HIGHAM, a citizen of the United States, residing in Philadelphia, Pennsylvania, have invented certain Improvements in the Prevention of Sparking in Electric Motors and Generators, of which the following is a specification.

The object of my invention is to so construct electric motors and generators that the non-sparking points of the commutatorcylinder can be automatically maintained no matter what may be the load of such machines within their capacities, and this without shifting their brushes. This object I accomplish by winding on the field-magnet pole-pieces of the machines counter distorting-coils, whereby the magnetic field is shifted in accordance with variations in the load to maintain the non-sparking point without shifting the brushes, as more fully described hereinafter. Y

In the accompanying drawings, Figure 1 represents a machine having its pole-pieces provided with electro-magnetic coils; and Figs. 2, 3, 4, and 5 are diagrams showing different ways in which such coils can be wound on the pole-pieces.

In Fig. l, A is the armature, with brushes a, which may be carried by a fixed holder.

E are the field-magnets, and P are their pole-pieces, 011 which I wind counter distorting-coils C in any convenient way, such as indicated in the different views in the drawings. The n and 3 signs indicate the polarity of these coils, while the N and S signs indicate the polarity of the field-magnet coils.

The arrows D in Figs. 2, 3, 4, and 5 indicate the direction of rotation of the armature when the machine is working as a dynamo or generator, while the arrows M indicate the direction when it is used as a motor.

It will be seen that in those portions of the pole-pieces where the polarity of the polepiece coils and the polarity of the field-magnet coils are of the same sign the magnetic field between the armature and such portions will be greater than the magnetic field between the armature and those portions where the polarities of the pole-piece coils and the field-magnet coils are of different signs. Therefore the magnetic field will be shifted toward those portions where the polarities are of the same sign.

In constant-potential machines the sparking is due to the varying armature-current. Therefore, if the counter distorting-coils C on the pole-pieces are connected in series with the armature-coilsas shown in Fig. 1, for instancethe magnetic field will be shifted in proportion to the armature-current. The an mature-coils which are short-circuited by the commutator-brushes are thus automatically made to out such magnetic lines as to counterbalance the self-induction of the said armature coils, and so prevent consequent sparking. In constant current machines (where the regulation is accomplished by varying the magnetic intensity of the field-magnet) the sparking is similarly prevented; but in this case the pole-piece coils are supplied with a constant current, the magnetic field being shifted by the varying magnetic intensity of the field-magnet. For instance, when there is little or no current traversing the field-magnet coils, and when the pole-piece coils have their full current, the magnetic field set up will be the most distorted or shifted; but when an intense current is traversing the field-magnet coils (remembering the current of the pole-piece coils to be constant) the magnetic field will be Very little distorted or shifted on account of the magnetic action of the pole-piece coils becoming smallerin comparison with the increased magnetic action of the field-magnet coils. These counter distorting-coils can therefore be so proportioned by experiment that the magnetic field will be so shifted that the armaturecoils which are short-circuited by the commutator-brushes will always find themselves in a magnetic field, which will counteract the self-induction of the said armature-coils and avoid sparking.

I claim as n1y-invention An electric motor or generator having fieldmagnet coils on its cores and counter distorting-coils on its pole-pieces, as and for the purpose set forth.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

DANIEL HIGHAM.

Witnesses:

WILLIAM D. CONNER, HARRY SMITH.

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