GB639059A - Frequency converter - Google Patents

Abstract

639,059. Frequency changing; transformers. AUTOMATIC ELECTRIC LABORATORIES, Inc. Aug. 8, 1947, No. 22007. Convention date, Aug. 15, 1946. [Class 38 (ii)] A frequency changer has a ferromagnetic core carrying a primary winding and a resonant secondary winding through both of which windings two legs of the core pass, the arrangement being such that the magnetic fluxes in the two legs link the primary winding in the same sense, but link the secondary winding in opposite senses and vice versa, the two legs being of materials of different permeabilities. The core comprises two crossed laminated legs, one, SI, of silicon iron, the other, AL, of a nickel iron material and the primary winding 1 is wound through diagonally opposite openings, the secondary winding 2 being wound through the other diagonally disposed openings. Additional windings 1a, 1b are provided to ensure that the knee of the magnetization curve for the silicon iron is raised to correspond with that for the allegheuy electric metal. The same effect can be obtained without additional windings, but making the allegheny electric metal leg to have a smaller cross-section than the silicon iron leg. Thus there is practically no mutual induction between the two windings below the knee of the curves, transference of electrical energy only taking place when the legs are working above the knee of the magnetization curves, the frequency of the output circuit being determined by the resonant frequency of the secondary circuit, i.e. by the value of the condenser 5. In order to render the apparatus self-starting, a thermionic valve is provided which supplies an initial rectified current pulse to saturate the core after which the circuit is self maintaining under normal conditions and the valve is then biassed back beyond cut-off. If, however, the apparatus becomes overloaded, the valve is arranged to supply rectified current pulses every half-cycle until the overload is removed. Alternatively, an electromagnetic relay may be used instead of the valve. Specification 599,880 is referred to.