possible sets of voltage frequency v f combinations representing various sine waves and realizes any voltage level desired for a given frequency without memory means moreover the arrangement assures a stable inverter operation fig3 illustrates the necessity of varying the motor speed and torque independently to respond to a widely varying capacity and torque load demands encountered in the real world for a higher motor efficiency fig4 illustrates the v f pattern segmentation made in this embodiment to satisfy both the aforementioned varying torque and near constant carrier frequency characteristics the maximum and minimum frequency and voltage applicable to the motor windings are specified by the electrical motor hardware carrier frequencies should be at least ten times as high as the fundamental sine wave frequencies this is because then the carrier frequencies are attenuated and smoothed out by the motor windings 44a through 44c by their ten times as high impedances exhibited as the fundamental frequencies this results in a sine wave with less distortion and consequently higher efficiency and lower noise and vibration of the motor center carrier frequency is arbitrarily selected at 1 2 khz to match the highest fundamental frequency of 125 hz the carrier frequencies are controlled to fall between 0 9 khz and 1 5 khz range in the embodiment of the present invention notice in.