| 摘要 |
PROBLEM TO BE SOLVED: To shorten the time required for restarting by detecting a residual voltage when a motor is in the free-running condition, obtaining a corrected number of rotation instructing value by obtaining the frequency and phase from such residual voltage, and then forming a gate signal. SOLUTION: A residual voltage when a motor 11 is in the free-running condition is detected with a transformer 13 for a gage and a velocity setting device 17 obtains the corrected number of rotations command value obtaining frequency and phase from such residual voltage. A gate signal generator 18 generates a gate signal based on a timing matching signal for matching the corrected number of rotation instruction and the phase, and then outputs this gate signal to a VVVF device 12, and the ignition timing of the switching element can be changed. Accordingly, an AC power synchronized with the residual voltage during the free-running may be supplied from the VVVF device 12, and the number of rotation instruction value comes near to the actual number of rotations of the motor 11. The time required to restart the motor 11 can be shortened with improvement in the tracking ability to velocity. |
