GB633769A - Improvements in frequency converters - Google Patents

Abstract

633,769. Frequency changing. BRITISH THOMSON-HOUSTON CO., Ltd. June 26, 1946, No. 19133. Convention date, June 27, 1945. [Class 38 (ii)] In a frequency converter, a condenser in series with the primary of a transformer across an A.C. supply is periodically charged and discharged to produce A.C. of a different frequency in the transformer secondary. In the single-phase case, Fig. 2 (not shown), a vibrating switch or synchronously-driven commutator alternately makes the primary circuit and breaks it while short-circuiting the condenser. Fig. 3 shows connections for the three-phase case, in which alternate segments 22, 22<1>, 24, 241 of a commutator are connected to appropriate slip-rings 18, 19, 20 fed from the supply 15, 16, 17, the other segments 21, 21<1>; 23, 23<1>, being connected together in pairs. When the commutator and slip-rings are rotated by motor 14, brushes 25, 26 engage the segments; upon contact with segments 22, 22<1>; 24, 241 &c., voltages represented by vectors 29 ... 34 in Fig. 4 are connected across the primary of transformer 1 and condenser 2, which is charged, and upon contact with segments 21, 21<1>; 23, 23<1> the condenser is discharged. Rocking of the brushes may provide regulation.