GB448341A - Improvements in frequency changing arrangements for supplying high-speed rotary field motors - Google Patents

Abstract

448,341. Frequency changing; phase changing. SIEMENS-SCHUCKERTWERKH AKT.-CES., Siemensstadt, Berlin. Dec. 5, 1934, Nos. 34962 and 34963. Convention dates, Dec. 5, 1933 and May 9, 1934. [Class 38 (ii)] Relates to a frequency - chanching arrangement for supplying a high speed motor from a 3-phase supply and consists in employing n saturated transformers the primary windings of which are arranged so that the fluxes generated are 60‹/n phase displaced from each other, the secondary windings being connected to the phase windings of the motor. In the form shown the transformers 6, 7 have open delta secondaries so that 3rd harmonic voltages only are present on the secondary side, and the primaries are respectively star and zigzag connected so that the 3rd harmonic voltages are 90‹ out of phase. Chokes 8 may be connected in series with the supply and condensers 9 in parallel. In addition condensers 10, 11 may be connected in series in the secondary circuits. In a modification the primaries of the two transformers are connected in series, and the cores united with a common yoke. In a modification the secondaries are suitably proportioned and arranged in Scott connection to give a three phase output. Condensers may be connected either in parallel with the secondary windings or in parallel with the 3-phase output. In a modification of this the windings are distributed over three three-limbed cores. In an alternative arrangement three transformers with primaries arranged to produce fluxes 20‹ phase displaced are employed to give a 3-phase output. Instead of employing an open delta secondary, a single winding arranged on the fourth limb of the core may be used.