GB703730A - Improvements in variable output voltage transformers - Google Patents

Abstract

703,730. Transformers. OAKLEY, J. L. D. (Marti, B. G.). Nov. 14, 1951, No. 26669/51. Class 38 (2) A variable voltage transformer having primary and secondary windings which are relatively movable to vary the output voltage of the transformer in dependence upon the load, the transformer comprising a pair of magnetic cores in face to face contact and relatively movable while maintaining a constant minimum air gap therebetween, the primary windings being mounted in grooves in one core, the secondary windings in grooves in the other core, and a number of short circuited windings mounted in grooves in one of the cores to compensate for stray fluxes. The transformer comprises a wound strip magnetic core 16 secured to a preferably non-magnetic yoke 10, the primary windings 23, 24 and the compensating windings 27, 28 being housed respectively in grooves, which are at 90 degrees to each other, in the contact face 17 of the core. A non-magnetic rod 31, secured to the yoke 10 forms a spindle about which a further preferably non-magnetic yoke 37 revolves, the yoke having secured thereto another wound strip magnetic core 43 also having grooves in its contact face 45 in which are housed the secondary' windings 48, 49. The relative positions of the primary and secondary windings are varied by rotating the core 43 with respect to the core 16, one suitable means of effecting this being as shown by an electric motor 56 and gearing 57, 58, 61, 55. Thus the coupling between the primary and secondary windings is altered whilst the reluctance of the magnetic circuit remains substantially constant. In order to reduce the friction between the cores the contact face of the movable core 43 may be relieved as at 44. The change in coupling may be dependent on any desired factors, such as variations in the load circuit, connected to the secondary windings 48, 49. In the polyphase embodiment of the invention a number of single phase structures as above may be used or one of the above structures may have the windings suitably modified. In the single phase embodiment the variation of the secondary voltage is in magnitude only, whilst in the polyphase embodiment the variation is in the phase between primary and secondary voltages. The transformer finds useful application as a normal induction regulator.