GB561367A - Improvements in magneto electric machines - Google Patents

Abstract

561,367. Ignition magnetos. BRITISH THOMSON-HOUSTON CO., Ltd. (General Electric Co.). Aug. 27, 1942, No. 12095. [Class 35] An ignition magneto of the inductor type comprises a core 18 carrying primary and secondary windings 11, 12, and having attached to its ends permanent magnets 21, the polepieces 22 of which extend towards the periphery of a toothed rotor 20 of magnetic material. The core 18 also has limbs, terminating in polepieces 19, disposed between the polepieces of the magnets. The pitches of the polepieces and of the teeth 23 of the rotor are such that when the magnetic circuit of one magnet is closed the circuit of the other magnet is opened ; thus when a rotor tooth is opposite the left hand magnet, as shown in full lines in Fig. 2, the magnetic circuit of that magnet is completed through the core 18, the left hand limb of the core and the adjacent rotor tooth, the polepieces of the left hand' magnet and the right hand limb of the core then being disposed midway between the rotor teeth. When the rotor has moved through a distance corresponding to half a tooth pitch, as shown by the dotted lines in Fig. 2, the magnetic circuit of the left hand magnet is closed, whilst the circuit of the right hand magnet is opened. The magnets may be formed of the iron-aluminium-nickel alloy described in Specification 423,897, [Group II]. The rotor teeth are preferably of less width than the polepieces in order that the voltage output may be maintained at low speeds.