METHOD AND CIRCUITRY FOR APPROXIMATING THE MAGNITUDE OF A VECTOR

A magnitude signal representing the approximate magnitude of a control parameter vector for the control of multi-phase electrical apparatus is developed from the Cartesian coordinate signals of the vector. Signals representing one or both coordinates of a plurality of auxiliary vectors are formed by vector rotation coordinate determination techniques. The signal from among the auxiliary vector coordinate signals (and, optionally the control parameter vector coordinate signals) having the greatest absolute value is selected as the magnitude signal. Auxiliary vector coordinate signals are formed by proportional stages coupled to adder stages which combine specified constant proportions of the control parameter vector coordinate signals. A diode network provides biasing so that only the signal with the greatest value will be passed. The auxiliary vector forming method for vector magnitude approximation provides accuracy and simplicity.