Several different types of variable frequency, variable voltage power supplies having a transistor chopper are known, but they all have singular disadvantages. Variable voltage inverters having a transistor chopper require an LC filter between the chopper and the inverter semiconductor switches in order to reduce motor current ripple and effect a stable system. Variable ratio, synchronized carrier, pulse width modulated (PWM) inverters having a chopper are known wherein the carrier steps through a sequence of ratios, or modulation modes, as motor frequency is varied. However, material transitions in motor performance occur as such variable ratio, synchronized carrier inverters step from one ratio to another, and further such inverters necessitate a complicated and elaborate control. PWM inverters having a transistor chopper are also known wherein each modulation frequency half cycle contains a fixed number of PWN chopper pulses regardless of motor speed, but the chopping frequency is so low at very low motor speeds, e.g., at 2 Hz, in such inverters that ripple occurs in the motor current and also chopping frequency is so high at high motor speeds that excessive dissipation occurs in the chopping element.