US604055A - Davies - Google Patents

Description

(No Model.)

2 SheetsSheet 1. W. LANGDON-DAVIES. ELEGTROMAGNBT HAVING ROTATING FIELDS. N0. 60 4,0 55.

Patented May 17,1898.

(No Model.) 2 Sheets-Sl1eet 2.

W. LANGDON-DAVIES.

BLEGTROMAGNBT HAVING ROTATING FIELDS.

No. 604,055. Patented May 17,1898.

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UNITED STATES PATENT OEEIcE.

IVALTER LANGDON-DAVIES, OF LONDON, ENGLAND, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE DAVIES MOTOR COMPANY, LIMITED, OF SAME PLACE.

ELECTROMAGNET HAVING ROTATING FIELDS.

SPECIFICATION forming part of Letters Patent No. 604,055, dated May 17, 1898.

Application filed May 28, 1896. $erial No. 592,831. (No model.)

To all whom it may concern: I to one another at an angle which is the sup- Be it known that I, WALTER LANGDON- plement of the phase angle between the fields DAVIES, a subject of the Queen of Great they produce a uniforoily-rotating resultant Britain, residing at 57 Oomeragh road, Vest of constant strength.

5 Kensington, London, in the county of Mid- I have also found that when the axes of any dlesex, England, have invented certain new two simple harmonic fields differing in phase and useful Electromagnets Having Rotating are inclined one to the other at an angle which Fields, of which the following is a specificais the supplement of the phase angle between tion. the fields they will produce the closest ap- [o In my prior application, filed November 7, proximation to a uniformly-rotating resultant 1895, Serial No. 568,201, there are described field of constant strength. It is therefore 60 means by which an alternating single-phase correct to place the axes of these fields at current may be made to produce a rotary ninety degrees when the phase difference is magnetic field suitable for a self-starting alninety degrees between the two fields. I have 15 ternating-current motor and suitable also for discovered, however, that when the difference atransformer whichis required to transforma is not ninety degrees the axes of the fields single-phase current into two approximately should be inclined to each other at an angle equal currents differing from one another in which is the supplement of that angle by phase. For these purposes, whether it be to which the magnetization of the two fields 2o obtain the greatest starting moment in an differ in phase. In general the difference of electromotor or the greatest efficiency in a phase to be taken into consideration for the transformer, the magnetic field should rotate above purpose will be that which exists inias uniformly as possible and should not vary tially; but if it is intended that the motor in strength. The means described in the said shall run asynchronously, as well as to be 25 specification approximately satisfy these conthus set in motion, it may be found advanditions, but greater uniformity may be obtageous to take the difference of phase when tained. the motor is at or about its normal work. It

I have demonstrated that when two fields is also importantthat the magnetic flux should are used to produce the rotating field the coils be as evenly distributed over the polar sur- 0 should be so set that the axes of the two fields faces as possible. Now, supposing an annular producing the resultant rotating field are in field-magnet and a cylindrical rotormounted 8o clined to each other at an angle which is the within it, the axis of the field generated by supplement of that angle by which the curthe field-magnet through the rotor being verrents in the two coils differ in phase. Thus, tical, then this field may be represented by a 3 5 supposing the phase difference of the currents number of vertical lines drawn across the anin the coils to be forty-five degrees, (which is nular field-space, and these lines, which will 8 5 about the maximum dilference of phase which decrease in length from the center line or diis suitable and is readily obtained from one ameter to either side, will approximately rep- I electromotive source,) the coils should be so resent the reluctances of the magnetic paths 0 set upon the core that the north pole of one across the various elements of the field. If

field is one hundred and thirty-five degrees now the same magnetomotive force be apfrom the north pole of the other field. Thus plied over the whole field by surrounding the two equal fields having simple harmonic vafield-space with a single coil, a stronger magriations which are not in phase with one annetic field will be generated through the reother are combined to produce a rotary field gions of lesser reluctance, and as a result the of which both the strength and the velocity of field generated by the above-described field- 5 rotation are constant. magnet will be considerably denser at the two The law is general that when the axes of sides than in the center.

two equal simple harmonic fields are inclined Figure 1 illustrates the usual method of applying a winding to a cylindrical field-magnet and indicates the nature of the magnetic field so obtained. Fig. 2 illustrates the usual method of applying two windings when a rotating field is required. Fig. 3 illustrates the new method of winding as applied to the production of a single alternating field. Fig. 3 is a diagram by the aid of which the proper distribution of the winding is ascertained. Fig. at is a modification of Fig. 3. Fig. 5 is an explanatory diagram. Fig. 6 illustrates another modification, in which the winding is divided into equal sections and the holes to receive it are not equally spaced. Fig. 7 illustrates the winding of a four-pole field-magnet, the winding being divided into equal sections. Fig. '7 explains the winding of a four-pole field-magnet, the holes being equally spaced. Figs. 8 and 9 illustrate the winding for a rotating field, in which the two component fields are at right angles, and the difference between the phases of the currents is also ninety degrees. Fig. 10 illustrates the winding for a rotating field where the difference between the phases of the currents is fortyfive degrees. Fig. 10 represents the currents in the two field-windings displaced forty-five degrees in phase. Figs. 11, 12, and 13 show the rotor which I employ.

Fig. 1 shows an end view of an iron cylinder such as would be used in a motor wound with a single coil to produce a field perpendicularly across the interior diameter. The conductors are wound through the holes at the sides of the cylinder, say up in a direction parallel with the axis through the hole on the left-hand side A, across the end of the cylinder in a semicircle, and down through the right-hand hole B, again in a direction parallel with the axis. Now with such a winding when the current passes polarities ,N and S are obtained, but the field is not at all uniformly distributed for the reason already given namely, the different reluctances of the pathsand the field is very dense at the two sides near A and B and diminishes very considerably toward the center, as is indicated by the figure. Now it is a fact (as might, indeed, be anticipated) that a uniform rotating field cannot be obtained by superposing, as in Fig. 2, two fields, such as Fig. 1 indicates, which are not individually uniformly distributed.

Fig. 3 illustrates my method of winding, by which I obtain approximately uniform distribution in each of the individual component fields. I distribute the winding so as to compensate the different reluctances of the paths. A portion only of the winding is threaded through the holes A B, while another portion is threaded through holes 0 D, and, it may be, a third portion through holes E F, and a fourth portion through holes G II. Then the windings O D E F G II will successively reinforce the magnetomotive force in those sections of the field which need reinforcement in conse quence of the progressive increase in the reluctance. The dotted lines indicate the directions taken by the winding Wires in passfrom hole to hole.

The number of the sections into which the winding is divided may be varied. Three will be sufficient for the smallest class of two-pole motors, and four or more sections will he used in two-pole motors of larger size.

The cylinder is built up of thin disks of soft iron, having sixteen holes in each, and is adapted to receive two similar windings, one above and the other below the horizontal diameter of the cylinder as it appears in the figure, each winding being in four sections and similarly situated. These windings above and below may be regarded as parts of a single coil. It is not essential, however, that the windings should be thus arranged. There need be no winding on the lower part of the cylinder, or the lower part of the cylinder may be reserved to receive a winding for a current differing in phase to produce with the first winding a resultant field of different phase from the first, or, again, the winding on the lower half may be omitted and the upper winding may be then redisposed, as in Fig. 4, partly on the upper and partly on the lower half of the cylinder.

The rule by which I apportion the turns in the several sections for a cylinder such as Fig. 3 is the following: Draw a figure such as Fig. 3, in which the points A B O D E F G H on the circumference of a circle correspond to the equally-spaced holes similarly lettered in Fig. 3. Bisect the intervals between the holes in points 1, 2, 3, 4-, and 5, marked on the circle. From the neutral point 1 draw a radius, and from the point 5 at the center of the polar surface draw another radius. They meet at the center 0 in a right angle. Draw a line 2 6, so that the angles at- 6 are right angles. Draw right angles 6 2 7, 2 7 3, 7 3 8, 3 8 4, and 8 e 9. Then the lengths of the lines 2 (5, 3 7, 4 8, and 5 9 represent and are proportional to the numbers of turns which should be wound through the holes A B, O D, E F, and G H, respectively. Thus I find, for example, that if I wind through A B nineteen turns I should wind through OD sixteen turns, through E F ten turns, and through G H five turns, these being the nearest whole numbers. I give to the winding GII the advantages of fractional parts. Similarly I calculate when the number of sections is less or greater than four.

The rule given above is readily deduced from the fact that the reluctance of two paths (represented in Fig. 5 by lines 3 and Varies approximately as the sines of the angles Y and Z. I therefore apply a proportionately greater magnet-motive force about than along 1/.

It will be observed that neutral intervals occur between the upper and the lower windings. It is expedient to provide in this manner for neutral areas between the polar surfaces.

'ameter of the armature-space.

When the total number of turns to be wound on is but small, sufficient accuracy cannot be obtained with equally-spaced holes. I then prefer to Wind an equal number of turns in each section and to vary the distances between the holes. Such a field-magnet may be set out in the manner shown in Fig. 6. The diameter of the armature-space coinciding with the axis of the field is divided into twice as many equal parts as there are coils to be wound,(in this case sixteen.) At right angles to the axis of the field are drawn parallel lines through the points 2 4t 6 8 1O 12 14; 16, cutting the di- Through the points where these lines cut the diameter are drawn radii, and the holes for winding are punched upon these radii. As shown, these holes are bisected by the radii. I can in a similar manner wind a-cylindrical magnetcore so as to obtain four or more poles. Fig. 7 shows a cylinder prepared to receive a fourpole winding.

In the case of afour-pole magnet when the holes are equally spaced and the number of turns on the coils differ from one another, as in Fig. 3, I ascertain the proportions to be given to the several sections of the windings by drawing a diagram such as Fig. 7. It is very similar to Fig. 3; but now the radii 5 O and O 1 meet in an angle of forty-five degrees. In other respects the description of Fig. 3 applies.

I have up to this point assumed that the air-space between the polar surfaces of the magnets Was free from iron. It is, however, at once obvious that the introduction of the iron rotor or armature will alter the problem only in degree and not in method of solution. The presence of the iron rotor does not alter the conditions except by lessening the total amount of the magnetic reluctance. Whether in iron or in air the longer course has the greater reluctance.

I have so far described the winding for obtaining one uniform field. To yield a rotating field, a second winding is required, separated from the first winding by an angular distance dependent on the diiference of phase in the two windings, as already explained. I can apply the second winding over the first, using the same holes, or some of them, to accommodate both the windings. Thus in Fig. 8 the full lines show a cylinder set out with holes for winding, as in Fig. 6, except that in this case the windings are to be each in five sections. The dotted lines show the holes repeated at ninety degrees distance from the holes represented by the full lines. The phase difference between the currents in the coils is in this case assumed to be ninety degrees. It is obviously impracticable to punch the double set of holes as they occur in this diagram. Fig. 9 shows the arrangement of holes suit able to receive two windings, the one over the other and at right angles. The dotted lines crossing the central space represent diagrammatically one pair of windings and the dotted lines outside the central space represent the other pair of windings.

Fig. 10 shows the arrangement which is suitable for a motor in which the difference of phase in the two component fields is forty-five degrees and in which the current in the two coils is derived from the same source, the coils being adjusted to equal ampere-turns in the manner described in my before-mentioned application. The winding having terminals a a is placed, as shown, with its magnetic axis inclined one hundred and thirty-five degrees to the winding having the terminals b b. The variation in the number of turns is indicated by the varying thickness of the lines representing the windings.

Fig. 10 shows the currents in the two fieldwindings displaced forty-five degrees in phase. Thus the magnetic axes of the two windings are inclined to each other at an angle, (one hundred and thirty-five degrees,) the supplement of the angle (forty-five degrees) representing the difference in angles of lag of the currents in the two windings.

Figs. 11, 12,and 18 show a rotor which is suitable for use with field-magnets such as herein described. It consists of a series of iron disks threaded upon a shaft A and clamped fast between screw-nuts B. A feather O prevents the disks from turning on the shaft. A series of copper rods D are passed through the disks and at their ends are fixed into massive copper rings E. Saw-cuts are made in the edges of the disks parallel to the axis and penetrating into the holes which receive the copper rods. These slits are seen in Fig. 13. The thick black lines in Fig. 11 indicate in sulating material.

Field-magnets in accordance with this invention are also applicable to transformers.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is 1. An electromagnet energized from a single source of alternating electromotive force comprising two component fields of equal rates of alternation but with different phase angles of magnetization, having their magnetic axes inclined one to the other at an angle other than ninety degrees and equal to the supplement of that angle by which the currents in the two component windings differ in phase, thus producing a rotary field.

2. A11 electromagnet energized from a single source of alternating electromotive force, for an electric motor or transformer, comprising two component fields of equal strength and equal rates of alternation, but with different phase angles of magnetization, having their magnetic axes inclined one to the other at an angle other than ninety degrees and equal to the supplement of that angle by which the currents in the two component windings differ in phase, so as to produce a resulting rotary field of constant strength and of uniform rate of rotation.

3. A field-magnet for an electric motor or transformer, consisting of a substantially cy lindrical magnetic core, wound with coils of wire encircling varying amounts of the cylindrical field-space, the coils being distributed upon the cylinder in due proportion to the magnetic reluctance to be overcome in the central field-space, so as to produce a field of substantially uniform density, substantially as described.

4:. A field -magnet for electric motors or transformers consisting of a substantially cylindrical magnetic core,wound with two component windings,with their axes of magnetization inclined one to the other, each winding being composed of coils of wire encircling Varying amounts of the cylindrical field-space, the coils being distributed upon the cylinder in due proportion to the magnetic reluctance to be overcome in the central field-space, so as to produce aresultant field of substantially uniform density, substantially as described.

5. A field-magnet for electric motors or transformers, consisting of a substantially cylindrical magnetic core,wound with two component windings, carrying currents of different phase, the magnetic axes of the two component fields being inclined one to the other, each winding being composed of coils of wire encircling Varying amounts of the cylindrical field-space, the coils being distributed upon the cylinder in due proportion to the magnetic reluctance of the central field-space, so as to produce a rotary field of substantially uniform density, substantially as described.

6. A fieldmagnet for electric motors or transformers consisting of a substantially cylindrical magnetic core,wound with two component windings, carrying currents of equal magnetizing effects and rate of alternation but of different angles of lag, the magnetic axes of the two component fields being inclined one to the other at an angle equal to the supplement of that angle by which the currents in the component windings differ in phase, each winding being composed of coils of wire encircling varying amounts of the cylindrical fieldspace, the coils being distributed upon the cylinder in due proportion to the magnetic reluctance to be overcome in the central field-space, so as to produce a resultant rotary field of uniform density, constant strength, and uniform rate of rotation.

'7. An electromagnet having a rotating field resulting from two windings carrying currents differing in phase asymmetrically arranged upon the core and inclined the one to the other at an oblique angle which is the supplement of the angle by which the current in the two windings differ in phase.

lVALTER LANGDON-DAVIES.

\Vitnesses:

DEANSTON OARPMAEL, WILFRED OARPMAEL.

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