Nikola Tesla – Researchers Reproduce Electromagnetic Motor

Nikola Tesla’s Electromagnetic Motor

Nikola Tesla Patents were quietly released in 2017.

Independent researchers have used the designs From the patent to reproduce Nikola Tesla’s Electromagnetic Motor:

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Full Patent and Description

Original Patent

(No Model.) 2 Sheets-Sheet 1. 

NTESLA. ELEGTRO MAGNETIC MOTOR. No. 382,279. Patented May 1, 1.888. 


1 A i V I ATTORNEYS (No Model.) 2 Sheets-Sheet 2. 


ELEOTRO MAGNETIC MOTOR; N0. 382,279. Patented May 1, 1888. 

V v w 1 A l v ii Wm v n. H In: i|h W a ATTORNEYS. 

Nv PEYEBa Phololilhugnphor, Wauhingmn, D. c. 




SPECIFICATION forming part of Letters I’Patent No. 3232.279. dated May 1, 1888. 

Application filed November 30, 1887. Serial No. 256,561. (No model.) 

To all whom it may concern: 

Be it known that I, NIKOLA TESLA, a subject of the Emperor of Austria, from Smiljan, Lika, border country of Austriaflungary, now residing at New York, in the county and State of New York, have invented certain new and useful Improvements in Electrolriagnetic Motors, of which the following is a specification, reference being had to the drawings accompanying and forming a part of the same. 

In a former application, filed October 12, 1887, No. 252,132, I have shown and described a mode or plan of operating electric motors by causing a progressive shifting of the poles of one or both of the parts or elements of a motorthat is to say, of either the field magnet or magnets or armature, or both. I accomplish this by constructing a motor with two or more independent energizing-circuits, on the field-magnets,for example, and I connect these up with corresponding induced or generating circuits in an alternating-current generator, so that alternating currents are caused to traverse the motor circuits. By so doing the poles of the field-magnet of the motorare progressively shifted, and by their attraction upon a rotary armature set up a rotation in the latter in the direction of the movement of the poles. In this case, liowever, the rotation is produced and maintained by the direct attraction of the magnetic elements of the motor. I have discovered that advantageous results may be secured in this system by utilizing the shifting of the poles primarily to setup currents in a closed conductor located within the influence 0f the field of the motor, so that the rotation may result from the reaction of such currents upon the field. 

To illustrate more fully the nature of the in- Vention Irefer to the accompanying drawings.

Figure 1 represents in side elevation the operative parts or elements of a motor embodying the principles of my’invention, and in section the generator for operating the same. Fig. 2 isa horizontal central section of the motor in Fig. 1,the circuits being shown partly in diagram. Fig. 3 is a modified form of motor in side elevation. Fig. 4 isa central horizontal cross-section of Fig. 3. 

In Figs. 1 and 2, Ais an annular core of soft iron, preferably laminated or formed of insnlated sections, so as to be susceptible to rapid variations of magnetism. This core is wound with four coils, O O O O, the diametrically-opposite coils being connected in the same cir- 5 5 cuit, and the two free ends of each pair being brought to the terminals t and t, respectively, as shown. \Vithin this annular field-magnet A is mounted a soft-iron cylinder or disk, D, l on an axis, a, in bearings I) b, properly sup- 6o ported by the framework of the machine. The disk carries two coils, E E, of insulated wire,wound at right angles to one another, and having their respective ends joined, so that each coil forms a separate closed circuit. 

In illustration of the action or mode of operation of this apparatus,let it be assumed that l the annular field-magnet A is permanently magnetized, so as to present two free poles diametrically opposite. If suitable mechanical 7o provision be now made for rotating the fieldmagnet around the disk,the apparatus exemplifies the conditions of an ordinary magnetogenerator,and currents would beset up in the coils or closed conductors E E on the disk D. 7 5 Evidently these currents would be the most powerful at or near the points of the greatest density of the lines of force, and they would, 

as in all similar cases, tend, at least theoretically, to establish magnetic poles in the disk D at right angles to thosein the annular fieldmagnet A. As aresult of the well-known reaction of these polarities upon each other, 

a more or less powerful tendency in the disk to rotate in the same direction as that of the field-magnet would be established. If, on the other hand, the ring or annular field-magnet A be held stationary and its magnetic poles progressively shifted by passing through its coils C O properly-alternated currents, it is obvious that similar results will follow, for the passage of the currents causing the shifting or whirling of the poles of the field-magnet Ainduces currents in the closed circuits of the armaturecoils E E, with the result of 5 setting up a rotation of the diskD in the same direction of such shifting. Inasmuch as the currents are always induced or generated in the coils E E in the same manner, the poles of the disk or cylinder follow continuously no the poles of the annular field-magnet, maintaining, at least theoretically, the same relative positions. This results in an even and perfect action of the apparatus. 

In order that the system as a whole may be better understood, I shall now describe the mode or plan devised by me for producing the currents that effect the progressive shifting of the poles of the motor. 

In Fig. 1, B B are the poles or polepieces of an alteruatingcurrent generator. They are permanently magnetized and of opposite polarity. F is a cylindrical or other armature containing the independent coils G G. These coils are wound at right angles, so that while one is crossing the strongest portion of the field of force the other is at the neutral point. The coils G G terminate in the two pairs of insulated colleeting-ringsf andf,upon which bear the brushes 9 y. Four wires connect the motonterminals t and t with the brushes 9 and g, respectively. Then the generator is retated, the coil G will at the certain point shown in the drawings be” generating its maximum current, while coil G is neutral. Let it be assumed that this current is conveyed from the ringsf f to the terminalst tand through the coils O 0. Its effect will be to establish poles in the ring midway between the two coils. By the further rotation of the generator the coil G is brought within the influence of the field and begins to produce a current-,which grows stronger as the said coil approaches the maximum points of the field, while the current produced in the coil G diminishes as the said coil recedes from those points. The current from the coil G, being conveyed to the terminals 15 t and through coils C C, has a tendency to establish poles at right angles to those set up by the coils O C; but owing to the greater effect of the current in coils G O the result is merely to advance the poles from the position in which they would remain if due to the magnetizing influence of coils O 0 alone. This progression continues for a quarter-revolution until coil G G becomes neutral and coil G G produces its maximum current. The action described is then repeated, the poles having been shifted through one-half of the field,or ahalf-revolntion. The second half-revolution is accomplished in a similar ‘way, the same polarity being maintained in the shifting poles by the movement of the generator coils alternately through fields of opposite polarity. 

The same principle of operation may be applied to meters of various forms, and I have shown one of such modified forms in Figs. 3, 

and 4 of the drawings. In these figures, M M are field-magnets secured to or forming part of a frame, F, mounted on a base, I These magnets should be laminated or composed of a number of eleetrieallyinsulated magnetic sections, to prevent the circulation ofinduced currents and to render them capable of rapid magnetic changes. These magnetic cores or poles are wound with insulated coils O G, the diametrically-opposite coils being connected together in series and their free ends brought to terminals ‘6 t, respectively. Between the poles there is mounted, in beari ngs in the cross pieces G, a cylindrical iron core, D, which, in order to prevent the formation of eddying currents, and the loss consequent thereon, is subdivided ‘in the usual way. Insulated eonductors or coils are applied to the cylinder D longitudinally, and for these I may employ copper plates E E, which are secured to the sides and ends of the cylindrical core in wellknown ways. These plates or conductors may form one or preferably several independent circuits around the core. In the drawings two of such circuits areshown, formed respectively by the conductors E and, E, which are insu’ lated from each other. It isadvantageous also to slot these plates longitudinally, to prevent the formation of eddy currents and waste of energy. 

From what has now been given the operation of this apparatus will be readily understood. To the binding-posts t tare connected the proper circuits from the generator to cause a progressive shifting of the resultant magnetic poles produced by the magnets M upon the armature. Thus currents are induced in the closed circuits on the core, which, energizing the core strongly, maintain a powerful attraction betweenihe same and the field,which causes a rotation of the armature in the direction in which the resultant poles are shifted. 

The particular adval’itage oi the construction illustrated in Figs. 8 and 4 is that a concentrated and powerful field is obtained and a remarkably powerful tendency to rotation in the armature secured. The same results may be obtained in the form illustrated in Figs. 1 and 2, however, by forming polar projections on the field and armature cores. 

When these motors are not loaded, but running free, the rotation of the armature is nearly synchronous with the rotation of the poles of the field, and under these circumstances very little current is perceptible in the coils E E; but if a load is added the speed tends to diminish and the currents in coils E11 are aug mented, so that the rotary effort is increased proportionately. 

Obviously the principle of this invention is capable of many modified applicationsmiost of which follow as a matter of course from the constructions described. For instance, the armature-coils,or those in which the currents are set up by induetiemmay be held stationary and the alternating currents from the generator conducted through the rotating inducing or field coils by means of suitable sliding con tacts. It is also apparent that the induced coils may be movable and the magnetic parts of the motor stationary; butI have illustrated these modifications fully in the application to which reference has herein been made. 

In the case of motors wound with independent field and armature circuits and operated by shifting their poles, as described in my said prior application, I may by shortcircuiting the armaturecoils apply the .present invention in order to obtain greater power on starting. 

An advantage and characteristic feature of motors constructed and operated in accordance with this invention is their capability of al-‘ most instantaneous reversal by a reversal of one of the energizing-currents from the generator. This will be understood from a consideration of the working conditions. Assuming the armature to be rotating in a certain direction following the movement of the shifting poles, then reverse the direction of the shifting,which may be done by reversing the connections of one of the two energizingcircuits. If it be borne in mind that in a dynamoelectrio machine the energy developed is very nearly proportionate to the cube of the speed, it is evident that at such moment an extraordinary power is brought to play in reversing the motor. In addition to this the resistance of the motor is very greatly reduced at the moment of reversal, so that a much greater amount of current passes through the energizing-circuits. 

The phenomenon alluded to-viz., the variation of the resistance of the motor apparently like that in ordinary motors-I attribute to the variation in the amount of self-induction in the primary or energizing circuits. 

These motors presentnnmerous advantages, chief among which are their simplicity, reliability, economy in construction and maintenance, and their easy and dangerless management. As no commntators are required on either the generators or the motors, the system is capable of a very perfect action and involves but little loss. 

I do not claim herein the mode or plan of producing currents in closed conductors in a magnetic field which is herein diselosed,except in its application to this particular purpose; but 

What I claim is- 1. The combination, with a motor containing independent inducing or energizing circuits and closed induced circuits, of an alternating-current generator having induced or generating circuits corresponding to and connected with the energizing-circuits of the mo tor, as set forth. 1 

2. An electro-magnetic motor having its field-magnets wound with independent coils and its armature with independent closed coils, in combination with a source of alternating currents connected to the field-coils and capable of progressively shifting the poles of the field-magnet, as set forth. 

3. A motor constructed with an annular field-magnet wound with independent coils and a cylindrical or disk armature wound with closed coils, in combination with a source of alternating currents connected with the fieldmagnet coils and acting to progressively shift or rotate the poles of the field, as herein set forth.


Witnesses: I 



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