23,122. Maschinenfabrik Oerlikon. April 18, [Convention date]. Alternating-current commutator machines.- Relates to the speed-regulation and phase-compensation of shunt-excited single-phase motors having short-circuited brushes X1 and exciting- brushes Y1, the latter being connected to the secondary winding of an adjustable transformer T, the primary winding of which may be bridged across a varying number of sections or tappings S1 ... S12 of the uniformly distributed stator winding by means of switches K1, K2. The invention consists in decreasing the number of stator winding-sections bridged by the exciting- brushes when passing from synchronous speed to higher or lower speeds, and at the same time increasing the angle between the axis of the bridged sections and the axis of the brushes X1 towards one side or the other, the pressure at the exciting-brushes also being increased by adjusting the transformer T. For speeds up to synchronism, the contact-bar K1 rests upon the contacts a1, b1, and the bar K2 and the adjustable transformer contact K3 are moved towards the right, until, at synchronism, the bar K, stands upon the contacts a7, b, and the contact K3 stands upon the point C2. The primary winding of the transformer thus bridges the whole of the stator winding, and its transforming ratio is at a minimum. For speeds above synchronism, the bar K. remains upon the contacts a7, b7, whereas the bar K1 is moved towards the right and the contact K3 towards the left. The single sections of the stator and transformer windings need not be'equal to each other, and, in place of the transformer T, a single-coil transformer or a potential regulator may be employed. At starting, inductive or ohmic resistances, or a part of the stator winding, may be inserted between the brushes X1.
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