Abstract: Flux signals suitable for use in a control of an ac motor are generated as a function of the voltages and currents furnished to the motor. From sensed values of motor phase voltages and currents, signals representing the direct and quadrature values of motor voltage and current as well as total motor current are developed. Employing a closed loop path, these signals are utilized to develop signals representing the direct and quadrature components of the value of motor flux. The closed path develops a resistance signal representing the instantaneous motor resistance as a function of the total motor current and flux which resistance signal is employed in the development of the various flux signals.