GB658732A - Low frequency generator - Google Patents

Abstract

658,732. A.C. commutator machines. IGRANIC ELECTRIC CO., Ltd. April 25, 1947, No. 11125. Convention date, April 27, 1946. [Class 35] A commutator machine is made to yield low frequency A.C. by causing its field, which is fed from the output of the system, to oscillate. As shown for a single machine yielding single - phase current at L1, L2, the field coils 2 are connected in series with a suitable condenser 3 to produce the correct frequency of oscillation across the armature 1. A normally closed relay 5 is energized through a rectifier 6 from the machine brushes and serves to shortcircuit the condenser at starting until the machine has built up to a suitable voltage to start oscillating, and also at stopping, to short-circuit the condenser and prevent the dying oscillation destroying the residual flux of the machine. In a two-phase arrangement (not shown) the fields of two mechanically coupled commutator generators are fed from one of the machines through resistances and condensers of suitable values to produce the necessary phase displacement in the two field windings. Alternatively, each field may be fed from the armature of the other machine. A three-phase arrangement comprises three mechanically coupled machines, each field of which is excited from the armature of the next machine through a condenser and resistance giving a phase displacement of 120 degrees. Compensating windings or split poles may be used to reduce the effect of armature reaction.