Abstract: Three-phase power-conversion wherein the frequency output voltage is independent of the frequency of input voltage. One of three input terminals in a load powered by the apparatus is directly grounded. Each of the other two input terminals is supplied a sinusoidal voltage artifact from an appropriate transform circuit which is driven by a microprocessor, with one of these artifacts having a form 1.73.alpha.SinA, and the other having the form of 1.73.alpha.Sin(A+60.degree.), where .alpha. is the nominal amplitude of the source voltage and the Expressions A and (A+60.degree.) are the respective phase angles. Operation of the microprocessor controls output frequency.

Abstract: Apparatus for supplying from a single-phase, known-frequency AC source, three-phase AC power at the same frequency. The apparatus features circuitry which employs high-speed power switching with respect to only one phase of a three-phase load, with the result that only two high-speed power-switching devices (transistors) are required.