| 摘要 |
PURPOSE:To decrease line current and to reduce power consumption by a method wherein both V/F and motor winding connection are altered. CONSTITUTION:A star-delta selector switch 4, an adjuster 8 of V/F (Voltage/ Frequency) ratio at AC motor 3 terminals, and a V/F ratio selector switch 11 are furnished. The star-delta selector switch 4 changes the AC motor 3 winding connection, selecting the star for a low speed running and the delta for a high speed running. The V/F selector switch 11 selects command signals to alter the output voltage of the PWM inverter 2 so that the V/F ratio may be smaller in the low speed range and larger in the high speed range. Thus, motor winding connection modification and V/F ratio variation effected together result in a greatly decreased line current, ensuring a continuous torque characteristic suiting given loads even in the low speed range. |
