| 摘要 |
PURPOSE:To smoothly perform the pole change of a pole change induction motor by synchronously operating a variable voltage and variable frequency inverter, a pole change coil switching circuit and a speed instructing circuit and dividing and multiplying the instructing frequency in response to the pole change ratio of the motor. CONSTITUTION:A variable voltage and variable frequency inverter 24, a pole change coil switching circuit 14 and a speed instructing circuit 26 are synchronously operated, the first and second set frequencies are respectively determined by the first and second frequency setting units 40, 44 in response to the number of a poles change induction motor 12, and the instructing frequency is divided or multiplied by a frequency divider or multiplier 46 in response to the pole change ratio. In this manner, the number of poles of the motor is increased at a low speed time, and is decreased at a high speed time, thereby reducing the shock such as a speed variation at the pole changing time and performing a smooth switching. |
