Patent GB-190704988-A (GB)
Title: Improvements in Rotary Transformers Permitting the Transformation of Alternating Current into Continuous Current and vice versa.
Inventor: HEYLAND ALEXANDER
Filed: 1907-03-01
Granted: 1908-05-01
Abstract: 4988. Heyland, A., and Korda, D. June 20,1906, [date applied for under Patents Act, 1901]. Rotary converters ; homopolar machines ; brushes. -A rotary converter for converting either single or polyphase currents into continuous currents, or vice versa, combines the features of a continuous-current homopolar machine and an inductor alternator or induction motor. The machine is self-regulating and allows a current of constant voltage to be obtained whatever may be the variation of the alternating-current tension. In one form, Figs. 1 and 2, the homopolar stator a is provided with field coils c<1>, c<2>, and the rotor b with three pairs of collecting-rings d. The continuous-current system comprises twelve bars f<1> on the rotor and six bars f<2> on the stator. The bars f<1> are connected four by four in parallel with each of the pairs of collecting- rings, and thus form three groups in series. Diametrically opposite conductors f are connected in parallel, thus forming three groups corresponding to those on the rotor. The alternating-current winding g is located in the same slots as the conductors f<2> and is shown as a three-phase winding. The inner part of the stator is laminated, while the other parts may be solid. The rotor is provided with two polar projections h, by which pulsating electromotive forces may be induced in the winding g and in the continuous-current conductors f<1>, f<2>. The separate conductors of the winding g are suitably connected in series so that the resulting potential is an alternating potential ; by connecting the conductors f<1>, f<2> in series through the brushes e the pulsating currents therein combine to give a uniform current. The armature reaction of the alternating- current windings g is eliminated by strongly saturating the poles h and by reducing the width of the air-gap between the poles. To vary the ratio of transformation, the field of the machine may be split up into two parts produced by windings c<1> c<2>, Fig. 4, which are independently regulated by rheostats i<1>, i<2>. The alternating-current windings g are located at one or both sides of the stator, the rotor being formed with end polar projections h adjacent thereto. The middle part of the rotor is cylindrical, and the continuous-current windings are uniformly distributed. By varying the current supplied to the winding c<1>, the total flux across the homopolar air-gap may be varied independently of the field passing through the alternating-current windings g ; or by reversing the connexions of the winding c<1>, the resultant field across the homopolar air-gap may be reduced to zero. A variable ratio of transformation may also be obtained by superposing an ordinary bipolar or multipolar field on the unipolar field. In transforming low - frequency alternating currents into continuous currents, the machine is made capable of revolving at a greater speed, for example equal to double or other multiple of that of synchronism, by providing the rotor with a single-phase or a polyphase winding, which is either supplied with alternating or continuous current or is simply short-circuited. One modification is shown in Fig. 9, in which the right-hand part of the rotor supports short-circuited coils g<1> ; or the machine may be arranged so that the rods f<1> with their collecting-rings act as squirrel cage windings, in which case the alternating-current windings may be placed at the middle part of the stator, as shown in Fig. 1, the rotor being without polar projections. In another arrangement, Fig. 10, the alternating-current windings g are mounted on two or more adjacent stator projections, Fig. 16, each lateral projection being made half the size of the central projection, so that the field cut by the rods f<1> is always of the same intensity. The machine may be ventilated by making the ends of the polar projections pointed in the direction of rotation. The brushes are composed of thin strips of copper k, Fig. 14, forming a comb which is pressed by a spring upon the collecting-rings, which are of hard polished steel lubricated by plumbago &c. The machine is well adapted for use in electric traction, such as on locomotives or autocars, for electrolysis, and for extracting-machines in mines &c. The Specification in the original form as published under the Act of 1901 describes also the use of the same winding for both alternating and direct currents. This subject-matter does not appear in the Complete Specification as accepted.