| 摘要 |
PURPOSE:To make it possible to swiftly and smoothly restart an induction motor regardless of its state at the restoration of power supply, by judging the presence or absence of residual voltage when power supply is restored, and, if there is no residual voltage, by re-exciting the induction motor to check its state and then restarting it according to the state. CONSTITUTION:If there is no residual voltage when power supply is restored after an instantaneous power interruption, circuits 10, 11 are actuated, and an induction motor 3 is operated in accordance with a specified procedure. The specified procedure is as follows: The interruption of output is canceled, and then the motor is so operated as to obtain a specified voltage and frequency. After a certain time has passed, the output is interrupted again, and further a certain time is allowed. Then residual voltage is detected. If residual voltage is not zero, a soft start is caused by narrowing down output voltage according to set frequencies through circuits 6-9. Since the motor is restarted at a correct number of revolutions, calculated from the residual voltage generated by re-excitation, in this method, it can be automatically and smoothly restarted regardless of the conditions of load. |
