Abstract: The invention relates to an autotransformer for transforming a three-phase power supply into a nine-phase power supply, notably for use in a rectifier. The autotransformer is a, step-up or step-down transformer. For a step-down application, the three-phase input terminals E1, E2, E3. are connected to one of the three main windings in delta configuration, mounted on respective magnetic branches M12, M23, M31 of a magnetic circuit. Te main winding B12 of one branch has intermediate taps K1, K?1, K?1 from which auxiliary windings X31, Y23, Z31, mounted on the other branches, start. These auxiliary windings produce, on three output terminals A1, B1, C1, voltages one of which is in phase with the three-phase supply voltage at E1, the other phase-shifted by +40°, and the third by +80°. The number of turns in the auxiliary windings and the position of the intermediate taps are calculated so as to obtain this result.

Abstract: The invention relates to an autotransformer for transforming a three-phase power supply into a nine-phase power supply, notably for use in a rectifier. The autotransformer is a, step-up or step-down transformer. For a step-down application, the three-phase input terminals E1, E2, E3 are connected to one of the three main windings in delta configuration, mounted on respective magnetic branches M12, M23, M31 of a magnetic circuit. Te main winding B12 of one branch has intermediate taps K1, K?1, K?1 from which auxiliary windings X31, Y23, Z31, mounted on the other branches, start. These auxiliary windings produce, on three output terminals A1, B1, C1, voltages one of which is in phase with the three-phase supply voltage at E1, the other phase-shifted by +40°, and the third by +80°. The number of turns in the auxiliary windings and the position of the intermediate taps are calculated so as to obtain this result.

Abstract: A DC-DC converter is provided, for example of the voltage booster type, comprising a switch controlled for chopping the input signal, a transformer whose primary winding receives the chopped signal and a means for rectifying the signal delivered by the secondary winding of the transformer.The switch is in parallel across a series assembly formed by the primary of the transformer and a capacitor. The rectifier means comprises a bridge for rectifying a current flowing in both directions.