Inverter motor with sinusoidal starting currents, a new solution with 2 DC-links only

Inverter motors need only simple line and machine commutated power converters and have proven good performance for drives in the MW range. They cause high torque ripple, which is disturbing only at low frequencies, and require additional commutation devices under heavy start-up conditions. The also very economic cycloconverters are only useful for machine frequencies up to 40% of line frequency. The new proposed system combines the advantages of both drives with 2 DC links only. The same circuit operates as a cycloconverter at start-up and low frequencies of the motor, and as a current source inverter at high speeds. A switchover from one operation mode to the other without any transient reaction is shown. The additional expenditure compared to the conventional invertor motor is very small.<>