| 摘要 |
PURPOSE:To restart an internal pump by controlling a recirculating pump at the starting time so that the ration V/F of the output frequency F of a power source to the output voltage V becomes larger than the value at the normal time. CONSTITUTION:The 3-phase AC voltage of a bus 1 is supplied through a stationary variable voltage variable frequency power source (VVVF) to an internal pump 5. A frequency controller 8 controls the output frequency of the VVVF3 proportionally to a speed request signal P. A voltage controller 12 controls the output voltage of the VVVF3 proportionally to the signal P. When the pump 5 is started, the signal P is set to a low value due to a low frequency start, but a bias signal is superposed to the input signal of a voltage controller 12 only at the starting time. As a result, the V/F value of the output of the VVVF3 becomes larger than the prescribed value, and the pump 5 can generate a large starting torque.
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