| Abstract |
Inverter motors use only simple line and machine commutated converters and have proved good performance for drives in the MW-range. They cause a high torque ripple, being 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. In this paper two circuits are described, whereby each system can be used at two operation modes: cycloconverter mode and inverter-motor mode. Each circuit operates like a cycloconverter at start-up and low frequencies of the motor, and as a current source inverter at high speeds. A soft and an abrupt switchover from one operating mode to the other without any transient is shown. |
