GB886092A - Electric motor - Google Patents

Abstract

886,092. Electric motors. BEREX ESTABLISHMENT. Dec. 16, 1959 [April 9, 1959; Sept. 29, 1959], No. 42740/59. Class 35. An electric motor, for either step-by-step or continuous operation, comprises a ferrite rotor 9 permanently magnetized with alternate poles around its periphery and a stator 5, 6 with triangular, interdigitated pole pieces 7, 8 which enclose a circumferential energizing coil 1. As shown, there is also an annular ferrite magnet 2 associated with the stator. Under the influence of this magnet the rotor assumes the position shown in Fig. 2, with its poles, shown shaded, beneath the appropriate stator poles. Energization of the coil 1 produces a flux opposite to that of magnet 2, overriding it, and causing the rotor to move one pole pitch. Subsequent de-energization of coil 1 restores the original flux and causes a further rotor movement in the same direction. It is stated that the shape of the pole pieces 7, 8 causes rotation to be in one direction only, to the right in Fig. 2. Thus, the rotor will step round in response to a series of pulses, or if the coil is energized with single phase A.C. the rotor will run in synchronism with the supply, and is stated to be self-starting. In a modification (Fig. 4, not shown) the magnet 2 is outside the stator. It is stated that a second coil may be provided in which current is induced while the rotor moves under the influence of magnet 2, and that this may be used to energize a second motor of this type. In an alternative arrangement (Fig. 5, not shown) the magnet 2 is replaced by a further coil which is energized in the opposite direction to the first and alternately with it through a switching device operated by a cam on the end of the rotor shaft. This arrangement will run continuously on D.C., e.g. for driving motor car auxiliaries such as windscreen wipers. The switching device may have a centrifugally controlled advance/retard mecha- -nism to ensure correct timing of the energizing pulses at all speeds. In a modification of this arrangement (Fig. 7, not shown) the two coils and the rotor are disposed in line along the axis of the motor. In a final arrangement (Figs. 9 and 10, not shown) for A.C. synchronous operation only, the stator is energized solely from a single coil and the triangular pole pieces touch their neighbours at their vertices.