| 摘要 |
PURPOSE:To stop an elevator accurately by operating a slip frequency based on a differential current on DC side of an inverter, between no-load excitation and constant speed loading of an induction motor for driving the elevator, thereby correcting a speed command and detecting the speed accurately. CONSTITUTION:Power from an AC power supply 1 is rectified 2 and smoothed through a capacitor 3 and then it is turned ON, OFF by means of a voltage type inverter 4 to produce VVVF power for driving an induction motor 5. A controller 6 comprising a microcomputer takes in DC current through a detector 11 and a current detecting circuit 12 and then a current/slip converting section 9 determines a slip frequency based on the difference of DC current under no-load and that under constant speed load. Output from a speed command operating section 8 is added with the slip frequency and fed to a voltage/ frequency command operating section 10 where the speed command is corrected and then the inverter 4 is turned ON, OFF through a base drive circuit 7. According to the invention, speed control is carried out accurately while compensating for the influence of load without requiring operation of load torque of the induction motor, resulting in accurate stopping of elevator. |
