US643066A - Alternating-current motor. - Google Patents

Description

Patented Feb. 6, I900.

W. LANGDUN-DAVIES.

ALTERNATING CURRENT MDTOR.

(Application filed. May 22, 1899.)

5 Sheets$heet I.

(No Model.)

Patehted Feb. 6, I900.

W. LANGDON-DAWES.

ALTERNATING CURRENT MOTOR.

(Application filed. HA)! 22, 1899.)

5 Shuts-Shoat 2.

(No Model.)

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No. 643,066. Patented Feb. 6, 1900. w. LANGDON-DAVIES.

' ALTEBNATING CURRENT MOTOR.

(Application filed. May 22, 1899.)

(No Model.) 5 Sheets-Sheet 3.

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No. 643,066. Patented Feb. 6, I900. W. LANGDON-DAVIES. ALTEBNATING CURRENT MBTOB.

(App ication filed May 22, 1899.) (No Model.) 7 5 Sheets-Sheet 4.

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N0. 643,066. Patented Feb. 6, I900. W. LANGDUN-DAVIES.

ALTERNATING CURRENT MOTOR.

(Application filed. May 22, 1899.)

(No Model.)

5 Sheats$heet 5.

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UNITED STATES PATENT OEEIcE.

WALTER LANGDON-DAVIES, OF LONDON, ENGLAND, ASSIGNOR TO THE LANGDON-DAVIES ELECTRIC MOTOR COMPANY, LIMITED, OF SAME PLACE.

SPECIFICATION forming part of Letters Patent No. 643,066, dated. February 6, 1900. Application filed May 22, 1899. Serial No. 717,810. (NomOdeL) To to 1071,0111, it 77211.7 concern:

Be it known that I,WALTEE LANGDON-DA- vIEs, electrical engineer, a subject of the Queen of Great Britian, residing at 101 Southwark street, London, in the county of Surrey, England, have invented certain new and useful Improvements in Alternating-Current Motors, of which the following is a specification.

The object of my invention is to produce an alternating-current motor from which a large starting effort can be obtained and the speed of which can be continuously regulated electrically and is not entirely dependent on the periodicity of the current.

My improvements are illustrated in the drawings annexed.

Figure 1 is an end elevation of a motor of the class to which my improvements apply. Fig. 2 is an end view of a ring-armature without any winding. Fig. 3 is a diagram end View of a motor constructed according to my invention. Figs. 4, 5, and 6 are similar diagrammatic views illustrating the effect of three different distributions of the field-windings. Fig. 7 is a diagram View showing how a magnetic field similar to that shown in Fig. 3 may be produced by-a different disposition of the field-windings to that shown in that figure. Fig. 8 is a diagram View of a motor such as shown at Fig. 3, but provided with two sets of field-windings, one to be used for running in one direction and the other in the other direction. In Fig. 8 the outer windings only which pass through the end slots in each pole-face are seen. In Fig. 3 these windings are somewhat bent aside, so that portions of the winding passing through the other slots may be seen.

The motor has two elements-one fixed, which I call the field-magnet, and one rotating, which I call the armature. Each element is wound with coils. The coils on one element are energized by the supply-current and induce current in the coils on the other element. When the coils on the fieldmagnet are energized by the supply-current, the armature is wound with coils in which currents are induced by the field-magnet, the coils are connected to a suitable commutator,

to the mains; b, the armature; c, commutatorbars, to which the armature-winding is coupled at intervals, and d d brushes connected to one another. The arrow 1 indicates the magnetic axis of the field-magnets, (it is shown as being horizontal,) and the arrow 2 the magnetic axis of the armature. It is in a line with the points of contact of the brushes. If the axes of the fields in the field-magnet and armature do not coincide, the field of the fieldmagnet and the field of the armature will repel one another, and a continuous rotation will result.

Motors on the general principles above de scribed have been made, but are inefficient.

In such an arrangement as that shown in Fig. 1 the reluctance in the path of a field having its axis on the line shown by the arrow 2 is greater than that of a field having its axis on the line shown by the arrow 1. There fore one of the fields would be weaker than would be the case if reluctance was the same for each field, and as the power is derived from the reaction of these two fields upon one another there would be less power obtainable, and therefore an arrangement such as shown in Fig. 1 must necessarily be very imperfect.

In motors working upon the above general principle I according to my invention wind the field on a continuous ring of iron having no projecting pole-pieces and suitably laminated and provided with slots or holes to receive the windings, as shown in Fig. 2, and for the reasons hereinafter stated I also so dispose the windings as to make the magnetic density uniform over or strongest at the center of each pole-face. It may be assumed in such a machine of fixed dimensions as has through each slot.

been described that the torque or turning effort with a given strength of ind ucing-field is proportional to the amount of current flowing in the induced windings, provided the brushes are fixed in position. I find that the amount of current induced in the induced windings by a given total strength of inducing-field may vary considerably with the way in which the inducing-field is distributed over the pole-faces and that the best results are obtained by so distributing the field-windings as to make the magnetic density strongest in the center of the pole-face and decreasing at the outer edges, as indicated by Fig. 3, in which the dotted lines represent, diagrammatically, the lines of force. To produce this result, I may wind my inducing-field in sec tions, so that the iron is surrounded by different numbers of turns, which increase the magnetic density toward the center of each pole-face. The field-windin g required to produce such a field will vary more or less for different sizes and varied forms of the motor;

' but generally to produce such a magnetic field one turn of the field-winding may, for example, be passed through slots marked No. 1 in Fig. 3 and be available for more or less magnetizing the whole of the iron in the space between these slots. Another turn of the winding may be carried through the slots No. 2 and be available for increasing the magnetization of the iron in the space between them, and so on to the slots No. 8, near the center of the pole-face. The induction density can then be tested by means of an exploring-coil in the known way, or the armature itself may be used as the exploring-coil and the voltage fordifferent positions of the brushes be taken. The information so obtained will indicate what corrections have to be made in the proportioning of the field-windings to produce the field required.

To illustrate the eifect of different forms of winding, I have in the diagrams Figs. 4, 5, and 6 illustrated approximately the electrical and magnetic conditions produced by Various forms of winding. In Fig. 4 the magnetic density is shown as being greater toward the ends of each pole-face than at the center. In Fig. 5 the density is uniform, or approximately so, over the pole-face, (directions for so proportioning the windings as to produce a uniform magnetic density are given in the specification of a former patent, issued to me May 17, 1898, No. 604,055,) and in Fig. 6 it is greater at the center than at the ends, and this is effected by passing a greater number of turns of winding through the slots which are near the center of the pole-face than would be required to produce uniform density, as in Fig. 5. Approximately it is desirable in most cases that an equal number of turns or windings should be passed The figures diagrammatically represent a two-pole motor. In each of the figures, a is a field-magnet ring. b is the armature, having sixteen teeth. The armature is shown wound with a continuous ring-winding having one turn wound in each notch between the teeth. This winding is shown connected in the usual manner to a sixteen-part commutator c. The dotted lines from the field-magnet through the armature and back to the field-magnet represent the magnetic field. The different numbers of lines entering each tooth of the armature are intended to graphically represent the density of the magnetic field over the pole-faces. The whole upper half of the inside face of the field-magnet is considered as one poleface and the lower half as the other pole-face. There is no gap in the iron between them. In other words, these are not what are to be understood as projecting poles. It is assumed in the following deductions that one magnetic line of force alternating in one turn of the armature-winding produces a potential ditference of one volt at the terminals of that turn-that is to say, in the winding shown, having one turn between each commutator-segment, the volts between each pair of commutator-segments are equal to the number of magnetic lines alternating through the turn of winding between them. The volts between the pairs of commutator-segments are written above the commutator in each of the figures, and the directions of the arrows show the relative directions in which current would flow. In each of the figures the same total number of magnetic lines is assumed to be produced by the field-magnet and to pass through the armature. By adding the volts between the sectors, giving them their positive or negative values, as shown by the direction of the arrows, the volts between a pair of brushes placed at the ends of any diameter of the commutator can be calculated. The maximum volts obtainable in Fig. 4 are forty-four, in Fig. 5 sixty-four, and in Fig. 6 eighty-four. As the only difference in the construction of the three figures consists of the diiferent distribution of the inducing magnetic field it is obvious that the greatest induced current, and therefore torque, can be obtained from the arrangement shown in Fig. 6. A practically similar magnetic field having the lines of force concentrated to the central portion of each pole-face can, as shown at Fig. 7, be produced by winding the central portion only of the pole-face with a single coil. In such a case it will not be necessary to wind the inducing-coils in sections, but, as shown, the central portion only, not exceeding or much exceeding one-half of the poleface, may be Wound with a single coil.

The magnetic distribution obtained by such a field-magnet as that shown in Fig. 1 may effectively resemble that shown in Fig. 7; but owing to the gaps in the magnetic circuit the gain by distribution will have to be set off against the losses arising from the reluctance of the path of the field set up by the induced current.

If the armature-windings are connected to IIO the source of supply by means of the brushes, the distribution of the field set up by the armature will be similar to the inducing-field shown in Fig. 6, since the armature-windings are distributed over the pole-face, though the position of its axis will depend on the position of the brushes. Hence it is apparent that to produce the same results the same construction must be used, whether the fixed or rotating part, or both of them, be energized by the supply-current.

The proportions of turns in the sections and the most suitable distribution for the field may, as above stated, be found by experiment and will vary for different sizes of motors and for the different kinds of work they are required to perform; but the field should always be banked to the center, as in Figs. 6 and 7, by means of the winding and without projecting poles.

Although I have only shown my improvements applied to a two-pole machine, it is evident that they may be applied to machines having a greater number of poles.

The motor may be controlled as to speed and power by introducing choke or resistance into the induced or inducing winding, either or both.

To change the direction of rotation of such a motor, I in some cases wind the field magnet ring, as illustrated at Fig. 8, with two sets of windings e f, set at an angle to one another such that the axis of the field produced by one set of windings 6 lies at a suitable angle to the axis of the other or armature-field to produce rotation in one direction and the field set up by the other field-windingf produces a rotation in the opposite direction. The magnetic field produced by the winding f is indicated by the dotted lines. In this way the direction of rotation can be controlled by a suitable switch exterior to the motor bringing into action one or the other set of windiugs, as required.

What I claim is 1. An alternating-current motor having its field-magnets formed in a drum-wound slotted continuous ring with no projecting polepieces and their windings so distributed as to make the magnetic density strongest at the center of each pole-face and having its armature wound with a continuous winding coupled at intervals to commutator-bars and also having brushes bearing against the commutator on a line inclined to the magnetic axis of the field-magnets and in which the circuit through the field-magnet windings and the circuit through the armature-windings and brushes are the one supplied with current and the other short-circuited.

2. An alternating-current motor having its field-magnets formed in a drum-wound continuous ring with no projecting pole-pieces and having the central portion only not exceeding or much exceeding one-half of each pole-face embraced by the field-windings and having its armature-windings coupled at intervals to the bars of a commutator and brushes bearing against the commutator on a line inclined to the magnetic axis of the field-magnets and in which the circuit through the field magnet windings and the circuit through the armature-windings and brushes are the one supplied with current and the other short-circuited.

3. An alternating-current motor having armature-windings coupled at intervals to comm utator-bars and brushes bearing on the commutator and having its field-magnets formed in a drum-wound slotted continous ring having no projecting pole-pieces and provided with two sets of windings one to be used when the motor is to run in one direction and the other when it is to run in the opposite direction.

WALTER LANGDON-DAVIES.

\Vitnesses:

ROBERT E. RANSFORD, JOHN H. WHITEHEAD.

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