GB276182A - Alternating current dynamo electric machine - Google Patents

Abstract

276,182. Weichsel, H. Oct. 18, 1926. Alternating-current motors; exciting; improving commutation, auxiliary means for. - An alternating-current motor has a primary winding 1 and a commutator winding 4 on the primary member, and on the secondary member exciting windings 5, 6 producing a number of poles greater than two, and the brushes on the commutator of like, polarity displaced by 360‹ or a multiple. thereof, are, joined by connections 15, 16 of such a resistance that no substantial current is carried thereby when the brushes are in contact with the commutator. The exciting windings 5 are in series with the positive brushes 7, 8, and the windings 6 are in series with the negative brushes. 9, 10. The brushes are displaced slightly from the axes of the windings for the purpose of obtaining a good synchronizing torque and powerfactor correction. The circuit between the positive and negative bushes is completed by a resistance 11 which interconnnects the middle points of the windings 5, 6. The stator is provided with starting windings 12, 13 closed through an adjustable resistance 14. At starting, the windings 5, 6 and 12, 13 act as polyphase secondary windings and the motor is brought to synchronous speed by reducing the resistance 14 to zero and the resistance 11 to a predetermined value. The resistances 15, 16 provide an alternative path for the current in the event of a momentary interruption in the electrical connection between a brush and the commutator and so sparking is reduced.