GB190523904A - Improvements in connection with Monophase Electric Motors. - Google Patents

Abstract

23,904. Elektrizitõts Akt.-Ges. vorm. W. Lahmeyer & Co. Nov. 21, 1904, [date applied for under Patents Act, 1901]. Motors, controlling.-Singlephase commutator motors working at variable speeds, for example, in driving either passenger- or freight trains, are run at low speeds either as repulsion motors or as series motor provided with compensating-brushes, and at high speeds as series motors with compensating field windings, with the object of securing sparkless running and a good power factor at all speeds. Fig. 4 shows the armature R of the motor and a supplementary field winding K supplied with current from the circuit of the main field winding W through a series transformer T, connexions being made to the contacts of a controller. In the position I of the controller, which corresponds to the motor working as a repulsion motor, the brushes a, bare short-circuited and the field coils W, K are placed in series through the intermediary of the transformer T, the brushes c, d being open-circuited. In the position II, the field coil K is open-circuited, the brushes a, b are short - circuited, and the brushes c, d are connected to the secondary of the transformer T, the motor operating as a series motor with compensating-brushes. In the position III, the field winding K is placed in circuit as before, and acts as a compensating-winding, while the brushes c, d are open-circuited, and may be removed from the commutator to avoid sparking. The motor then acts as a compensated-field series motor. The armature and field-magnet winding K may be directly fed from the field circuit W without the intervention of the transformer. The strength of the excitation field is varied according to the work to be done. For instance, if the work done by the motor in the positions I and III is the same, and it is desired to run at double the speed in the position III, the field excitation is reduced to one-half.