| 摘要 |
PURPOSE:To efficiently control an induction motor (IM) inexpensively by detecting a current between a power reactor and a smoothing capacitor and a current between the capacitor and an inverter, and detecting the exciting current component of the motor and the torque current component by the calculations. CONSTITUTION:Current detectors 7, 8 respectively detect currents ID, IA. A subtractor 9 subtracts a current I2' at no load time by the current ID. A calculator 10 calculates the ratio of the current ID' to the current IA, and generates a control signal (c) only when lower than a power factor set value cosphi*. A voltage controller 11 outputs a voltage command (v) output from a controller 6 to an inverter 4 while the signal (c) is not input as it is as v', and when the signal (c) is input, the predetermined value Vc is output as v' instead of a voltage command (v). Thus, the IM5 is always operated in such a manner that the power factor of the set value cosphi* or higher is held, thereby preventing the IM5 from generating an overexcitation. |
