| 摘要 |
PURPOSE:To generate a desired torque even when a power source voltage decreases by detecting the fact that a deviation between a current reference and a current feedback becomes the prescribed value or higher to correct a slip frequency and increasing the frequency applied to a motor. CONSTITUTION:An AC is used by a variable DC power source 3 as a DC through an inverter 6 to drive an induction motor 7. A signal of a speed detector 8 is compared with the value of a setter 9 to obtain a torque reference signal T, a current reference signal is compared with a main circuit current to control the variable DC power source 3, the fact that the control signal becomes the prescribed value or higher is detected by a detector 19, the output is added together with a voltage SV corresponding to the slip frequency obtained from a torque reference T and a speed signal VS, thereby controlling the inverter 6. Accordingly, even if the output voltage of the inverter decreased due to the power source voltage decrease, the applied frequency to the motor 7 increases, thereby generating the desired torque. |
