| 摘要 |
In switching from low to high speed operation, a driving electric motor (2) connected to a converter (1) connected to a commercial power supply (R, S, T) is disconnected from the converter (1) and then, with the residual voltage of the electric motor (2) dropped, the electric motor (2) is connected directly to the commercial power supply (R, S, T). Further, in switching from high to low speed operation, the driving electric motor (2) connected directly to the commercial power supply (R, S, T) is disconnected from the commercial power supply (R, S, T) and then, with the residual voltage of the electric motor (2) dropped, the electric motor (2) is connected to the converter (1). This makes it possible to achieve switching between low and high speed operations with an inexpensive arrangement and without a switching shock or noise. |
