Patent GB-190527260-A (GB)
Title: Improvements in Alternate Current Motors and Generators.
Inventor: FYNN VALERE ALFRED
Filed: 1905-12-30
Granted: 1907-01-30
Abstract: 27,260. Fynn, V. A. Dec. 30. Field magnets, special means for separately exciting; motors, controlling.- The power-factor of an alternating - current induction or conduction motor is improved or controlled by providing an adjusted field in the motor field axis or axes D-D, Fig. 1, by means of a stator winding or windings, on which is impressed a resultant electromotive force, the components of which differ in phase, the magnitude of at least one of them being independently adjustable. The invention is applicable to generators, which will work with a smaller drop on inductive loads, or the pressure may even be made to rise with increasing loads. In the single-phase motor shown in Fig. 4, the armature current is conveyed into the rotor R by means of a transformer winding S and shortcircuited brushes C, C, and the field winding FG is supplied from a phase converter AB with an electromotive force E' in quadrature with that of the mains and with a compensating electromotive force E<3> preferably co-phasal with that of the mains. The phase converter, preferably of the squirrel-cage induction-motor type, has a primary winding S<2> and two secondary windings F<1>, G<1>, the electromotive forces E', E<3> being regulated by varying the active turns of the windings F<1>, G', or by varying the electromotive force impressed upon the winding S'. The generator element A of the phase converter may be separated from the motor element B, as shown in Fig. 6, where a series characteristic is imparted to the main motor R by connecting the motor winding S<3> in shunt and the generator winding S' in series with the supply. Convenient starting and regulating devices X are placed in the circuits. In another modification, the exciting electromotive force E<2> is obtained from a phase converter, the compensating electromotive force being derived from the supply by means of an auxiliary winding disposed on the stator coaxially with the winding S, or from the winding S direct, or from a transformer connected in parallel with the mains. On the failure of a phase converter, the winding S, FG may be temporarily connected in series to produce a series induction machine. One phase converter may feed a group of motors. For starting and regulating the main motor, the transformer field may be varied, or an auxiliary electromotive force derived from the mains through a shunt transformer T, Fig. 12, may be impressed upon the brushes C, C. To avoid self-induction in the rotor circuit, the auxiliary electromotive force may be impressed upon a variable non-inductive resistance or capacity W. Fig. 8 shows a single-phase motor operated from a two-phase supply. The transformer winding S is supplied from one phase, while the winding FG is supplied with current from both phases, preferably through auto-transformers T', T'. In the case of a three-phase supply, the winding S is fed from one phase and the winding FG from the other two phases, or, Fig. 10, the stator is provided with a star-connected winding, the phases FG of which are connected so as to produce a magnetization along the motor field axis D-D. A winding G<1> co-axial with the winding S supplies the compensating electromotive force. A neutralized shunt conduction motor is operated from a three-phase supply in a similar manner. Fig. 15 shows a singlephase conduction motor having a transformer winding S, a winding K for neutralizing the armature self-induction, and a winding G<1> in series with the winding S, in which a compensating electromotive force E<3> is statically induced by the motor field. Two pairs of brushes short-circuiting the rotor in directions parallel to the axis D-D may be employed. A neutralized two-phase shunt conduction motor is also described. For traction purposes, the motors may be braked to return energy to the line. In all cases, two windings may be employed on the rotor. According to the Provisional Specification, Fig. 2, the exciting electromotive force E<2> and the compensating electromotive force E<3> may be supplied to two separate windings F, G arranged on the stator in the motor field axis D-D, or the rotor winding itself may do duty as a field winding by short-circuiting it along the axis D-D. To compensate for the inductive action of the winding F on the winding G, an additional electromotive force opposed to the electromotive force induced in the winding G may be impressed upon the latter, or an inductance and some resistance may be included in its circuit, or the pitch of the winding G is made smaller than that of the winding F. The windings F, G, S may be excited independently from the three phases of a threephase supply. Fig. 4 of the Provisional Specification shows a motor with a series characteristic having an-auxiliary winding S' in series with the winding S and co-axial with the winding FG, on which are impressed the electromotive forces E<2>, E<3>, or the compensating electromotive force E<3> only, the latter being in phase with E'. Modified arrangements of Figs. 4 and 6 of the Complete Specification are described in the Provisional Specification, in which the converter secondary windings F<1>, G<1> are replaced by a single winding having its axis inclined to the axis D-D. The motors may be operated by continuous current. For example, the motor shown in Fig. 6 would have the brushes C, C connected to the mains, the winding FG acting as the field winding and the winding S compensating for armature reaction. The power-factor of a series conduction motor provided with a compensating field winding is improved by means of an auxiliary stator winding co-axial with the main field winding and fed from the mains through a shunt transformer.