| 摘要 |
PURPOSE:To obtain a variable speed operating system with a less loss and a superior characteristic by a method wherein a bi-lateral control rectifier arranged between a power supply and an electromotor is switch-controlled to in steps generate frequencies lower than a supply frequency. CONSTITUTION:A three-phase AC power supply 1 is led to a transformer 2 for 3- phase.6-phase conversion and each output of the transformer 2 is connected to bi- lateral elements TH respectively of a control rectifier 3, whereby the output is fed as input to a 3-phase induction motor 4 and also the respective thyristor elements TH are switch-controlled by a frequency setter 6 and a gate control circuit 5. Accordingly, each phase output of the 3-phase and each phase output of the antiphases thereof are changed over with a cycle of more than the supply cycle, whereby frequencies in a range of around the supply frequency to two times the supply frequency are obtained in steps to enable the electromotor 4 to be driven and the variable speed operation can efficiently by performed. |
