| 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 electro-motor is switch-controlled to generate in steps 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 restifier 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, by switch-controlling each of the 3-phase and each antiphase of each of the 3-phase, voltages with the same polarity are changed-over for a period of more than one cycle of the supply cycle to obtain in steps the frequencies of less than 1/2 of the supply frequency, the electromotor 4 can be driven and the variable speed operation can efficiently be performed. |
