Inverter motor with sinusoidal starting currents

A power converter circuit for motor applications without substantial additional expenditure at the power circuit, with the exception of the DC link chokes, compared to the conventional inverter motor is presented. The circuit operates as a cycloconverter at start-up and low frequencies of the motor, and as a current source inverter at high speeds. A soft switchover from one operating mode to the other without any transient reaction is described. The drive system produces full torque without any ripple at lower frequencies. Torque can be controlled with good dynamic performance and without additional commutation devices. The principle of operation of a second power converter circuit, which uses DC link chokes with insignificantly higher expenditure compared to the conventional inverter motor, is described