Patent GB-190600238-A (GB)
Title: Improvements in Single Phase Alternate Current Commutator Motors.
Inventor: FYNN VALERE ALFRED
Filed: 1906-01-03
Granted: 1906-07-12
Abstract: 238. Fynn, V. A. April 15, 1905, [date applied for under Patents Act, 1901]. Field magnets; motors, controlling; sparking, preventing.-To facilitate the starting and speed regulation of single - phase motors which start and operate as repulsion motors or only start as repulsion motors and then operate as induction motors, the stator winding is built up of two or more sections connected in series and having their magnetic axes displaced with regard to each other. The position of the resultant field axis with respect to the axis of the repulsion brushes is varied by altering the proportion between the ampere-turns of the field section, by cutting out turns, or, preferably, by altering the grouping of the turns, for instance, by combining them in series-parallel relationships. In Fig. 2, the stator winding consists of two sections B, C displaced by #/n degrees, where n is the number of poles. The axis of the section B coincides with that of the repulsion brushes R, R, and the turns I, II of the section C used for starting are cut out by means of the lever H until the working position III is reached. The turns used for starting may be made of thinner wire than those used in normal working in order to save space and material, or all the turns in the section C may first be connected up in series and then in parallel. The direction of rotation may be changed by reversing the current in one of the sections B, C. In the modification shown in Fig. 3, the section B is replaced by two parts B', B<11>, the resultant magnetic axis b of which coincides with the brush axis. The three sections B', B", C are displaced from another by 4#/3n degrees, and are arranged somewhat after the style of a threephase winding. The motor is reversed by reversing the current in the sections B', B<11> or in C. Alternatively, the three sections may be regarded as separate and the direction of rotation determined by placing two sections in circuit at a time. The repulsion brush axis is placed coaxially with one of the sections and preferably with the one which is always in use to obviate shifting of the brushes. Fig. 6 shows the application of the invention to a repulsion-induction motor. The motor is started as a repulsion motor with the brushes K preferably open-circulated or closed through a high resistance. The turns of the section C are gradually cut out until the resultant field axis coincides with the repulsion brush axis, and the brushes K shortcircuited, when the motor runs as a pure induction motor. A compensating electromotive force derived from an auxiliary winding D upon the stator may be impressed upon the brushes K. The direction of rotation is reversed by means of switches S, S'. Instead of closing the brushes K through resistances, counter-electromotive forces may be employed, which may be used at the same time to compensate the motor, as described in Specification No. 22,712, A.D. 1902, any suitable transforming- devices being used if necessary. To relieve the commutator of current, the whole or two or more points of the rotor winding may be short-circuited as the normal speed is approached. When compensating the motor, a rotor winding of the kind described in the above-mentioned Specification may be employed.