GB197722A - Improvements in and relating to alternating current commutator machines - Google Patents

Abstract

197,722. Creedy, F. Feb. 13, 1922. Alternating-current commutator machines.- In an alternating-current commutator machine in which a phase-compensating voltage, derived from an auxiliary stator winding acting as secondary to the main stator winding, is impressed on the commutator, the auxiliary winding is distributed so that the turns in one pair of slots are connected in series with those in other pairs of slots symmetrically placed with respect to other poles before being connected in series with the conductors in a second pair of slots adjacent to the first pair. Taps may be provided on the auxiliary winding to enable the motor to run on different voltages. The auxiliary winding T<1>-T<5>, Fig. 1, is in series with the main winding S<1>-S<2> across the line and is tapped at T<2>, T<3>, T<4> so that when the contact A is moved the machine may be made suitable for different line voltages. The compensating voltage applied to the brushes X<1>, X<2> may also be varied by means of the contact A<1>. The windings S<1>, S<2>, T<1>, T<5> may be independent, the contact A being connected to the point S<2>, for high voltage supplies or, as shown in Fig. 2, the brush X<2> may be directly connected to the line, thereby giving a series connection between the rotor and stator coils. The contact A' is moved so that at full speed a greater number of stator turns, is included than before the brush X<2> is connected to the auxiliary winding, thereby giving a powerful starting flux and torque. A developed auxiliary stator winding for a 4-pole 28-slot single phase machine is shown in Fig. 3. Slots 4, 11, 18 and 25 are blank and each pole is defined by three concentric coils e.g. 1, 2, 3 and 5, 6, 7. The coil in slots 1, 7 instead of being immediately in series with 2, 6 is connected in series with 15, and 21, 28 and 22 and 14 and 8, symmetrically placed with respect to the other poles, before connection to 2, 6. The taps T<2> - - T<5> may thus be brought out in approximately equal steps from an uniformly distributed winding. Starting from terminal T<6> the winding makes one turn around each pole before tap T<5> ; then one around each pole and an extra one before tap T<4> and so on. The application to a two-phase winding is also described in the Specification.