Westinghouse Elec. & Mfg. Co. v. New England Granite Co.

• Citation: 103 F. 951
• Decision Date: 29 August 1900
• Docket Number: 919.
• Court: U.S. District Court — District of Connecticut
• Parties: WESTINGHOUSE ELECTRIC & MFG. CO. v. NEW ENGLAND GRANITE CO. et al.

103 F. 951

WESTINGHOUSE ELECTRIC & MFG. CO. v. NEW ENGLAND GRANITE CO. et al.

No.919.

United States Circuit Court, D. Connecticut.

August 29, 1900

Frederic H. Betts and Kerr, Page & Cooper (Leonard E. Curtis, on the brief), for complainant.

Mitchell Bartlett & Brownell, for defendants.

TOWNSEND District Judge.

Final hearing on bill and answer raising questions of patentability and infringement of complainant's three patents granted to Nikola Tesla May 1, 1888, namely, Nos. 381,968, 382,280 and 382,279. No. 381,968 is for an electro-magnetic motor. No. 382,280 is for the electrical transmission of power by the method of operation described in No. 381,968. Patent No 382,279 is for a specific construction of motor embodying the invention of the other two patents. It is not claimed that the defendant Batterson has infringed, and as to him the bill may be dismissed. The patents in suit relate to the art of electrical transmission of power by the use of mechanically generated alternating electric currents. It is, of course understood that the real nature of electricity is still unknown, and that the nomenclature used herein, such as 'currents,' 'flowing,' etc., are merely convenient technical terms to indicate certain known results. The electric current induced by a mechanical generator-- a dynamo-- is necessarily alternating in character; that is, alternating in direction, so that the current, acting on an armature, first tends to actuate it in one direction and then reverses said effect, and neutralizes such actuation. Such a current flows uninterruptedly and regularly, but rises in intensity from zero to maximum, and falls from maximum to zero, and then repeats said variations in the opposite direction. Its curve of increase or decrease of strength is indicated by a wave line or sine curve. Every mechanically generated current is naturally and originally an alternating current. Formerly it was not considered practicable to use mechanically generated currents until their alternations were straightened out by means of commutators, which reversed the direction of the current so as to make it flow continuously through the conductors. A current which is periodically reversed by a commutator which thus breaks the current between the changes in direction and takes off the current in sections, is known as a 'reversed' or 'alternated' current. This distinction between an alternating and an alternated current should be carefully noted. An alternating current continues to act in opposite directions as originally generated. An alternated current has been so reversed that the whole flows in one direction, and is then known as a 'continuous current. When so reversed by commutators as to become continuous, the current loses certain characteristics essential to its highest efficiency. Prior to the Tesla inventions, only reversed or alternated electric currents were used for the transmission of power. The application of this system for the transmission of power was limited, for various reasons; among others, because a large current could not be safely used at sufficiently high pressure for long distances. On the other hand, the pure alternating current was practically unlimited in volume and pressure, and a change of pressure could be economically effected by the use of a transformer. Prior to Tesla's inventions, however, these rapid alternations of the alternating current prevented the motor from starting its revolution, and interfered with its continuing in operation, except when in synchronism with the generator. It was, therefore, impracticable for varying loads.

The problem which was presented to Nikola Tesla, and which he successfully solved, was, how to overcome the difficulties attendant upon the use of the alternating currents so that their inherent vitality and untrammeled energy might be utilized for the unlimited transmission of power. In an electric motor the tendency of the armature is always towards the pole or point of maximum magnetic intensity. If a loosely-pivoted or freely-moving magnetic bar or armature be suspended midway between two coils of insulated wire wound in opposite directions on a soft iron bar, and one of the coils is electrically energized, north and south poles will be formed at the ends of the soft iron bar, their location depending upon which coil is energized; but, if both coils be equally energized, the two poles will neutralize each other, and cause a resultant north pole midway between the coils. If, now, the current in one coil be made weaker than in the other, said pole will move towards the coil of greater electrical energy. The magnetic bar or armature will follow the shifting position of the pole, and by thus gradually varying the energy in the coils the armature may be alternately caused to move from the pole of one coil along towards the pole of the other coil. The alternating current generated by an electrical machine, as before stated, constantly varies from maximum intensity to zero in one direction, and then from zero to maximum intensity in the opposite direction. In the invention of the patents in suit Tesla availed himself of this characteristic feature of alternating currents in the following way: In constructing a motor he arranged on an annular soft iron core to pairs of magnetizing coils, each pair at right angles to the other,--that is, one coil of one pair at the top, and one at the bottom,-- and one coil of the other pair at each opposite side of said core, and mounted an armature in the center. Then, connecting them with an alternating current generator, he caused a current from one pole of said generator to pass through one pair of coils and a current from the other to pass through the other pair. If the cycles of alternating currents be regarded as divided into 360 degrees, then, as shown in the Tesla illustrations, they will have a relative displacement of 90 degrees. In such position the lines of magnetic force traversing the two coils will be at maximum in one while at minimum in the other. This relative displacement marks the differing phase or time relation of the two currents. The effect of passing two equal currents through said coils would be to cause the pole of maximum intensity to pass midway between the poles of the respective pair of coils. But the effect of the ordinary operation of the generator, as before explained, was to cause the current in each pair of coils to vary from zero to maximum and to zero, and then to shift in the opposite direction; the intensity of the current flowing to one pair of coils being at maximum, while that of the other was at zero, and one increasing while the other decreased, and the result being to shift said poles so as to make them travel entirely around said core.

Fifteen days after the issue of the patents in suit Tesla read before the American Institute of Electrical Engineers a paper entitled 'A New System of Alternate Current Motors and Transformers,' in which, inter alia, he said:

'The transmission of power has been almost entirely confined to the use of continuous currents, and notwithstanding that many efforts have been made to utilize alternate currents for this purpose, they have, up to the present, at least as far as known, failed to give the result desired. * * * The subject which I now have the pleasure of bringing to your notice is a novel system of electric distribution, and transmission of power by means of alternate currents, affording peculiar advantages, particularly in the way of motors, which I am confident will at once establish the superior adaptability of these currents to the transmission of power, and will show that many results heretofore unattainable can be reached by their use; results which are very much desired in the practical operation of such systems, and which cannot be accomplished by means of such continuous currents. Before going into a detailed description of this system, I think it necessary to make a few remarks with reference to certain conditions existing in continuous current generators and motors, which, although generally known, are frequently disregarded. In our dynamo machines, it is well known, we generate alternate currents, which we direct by means of a commutator, a complicated device, and it may be justly said, the source of most of the troubles experienced in the operation of the machines. Now, the currents so directed cannot be utilized in the motor, but they must-- again by means of a similar unreliable device-- be reconverted into their original state of alternate currents. The function of the commutator is entirely external, and in no way does it affect the internal current machines, the currents appearing as continuous only in the external circuit during their transit from generator to motor. In view simply of this fact, alternate currents would commend themselves as a more direct application of electrical energy, and the employment of continuous currents would only be justified if we had dynamos which would primarily generate, and motors which would be directly actuated by such currents. But the operation of the commutator on a motor is twofold: Firstly, it reverses the currents through the motor; and, secondly, it effects automatically a progressive shifting of the poles of one of its magnetic constituents. Assuming, therefore, that both of the useless operations in the system-- that is to say, the directing of the alternate currents on the generator and reversing the direct currents on the motor-- be eliminated, it would still be necessary, in order to cause a rotation of the motor, to produce a progressive shifting of the poles of one of its elements, and the question presented itself how to perform this operation by the direct action of alternate currents.

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