| 摘要 |
PURPOSE:To reduce the current overload rate of an inverter, by performing voltage forcing in a low speed region at the time of starting and the like. CONSTITUTION:A V/F constant voltage reference generator 2 outputs a voltage reference of V2=kf at a frequency range of 0Hz - top frequency. Meanwhile, a forcing reference generator 3 outputs V1=nkf, at which the V/F ratio is forced by (n) folds, in a range of 0-F Hz. The generator 3 outputs a constant value V1=nkf at F Hz or more. A contact point 8 of a timer relay 7 is an OFF delay contact point. Therefore, the contact point 8 remains closed for (t) seconds after starting. Then, the forcing voltage reference V1 is inputted to a maximum value selector 4 during this period. The OFF delay contact point 8 opens (t) seconds after the start, and the voltage reference is returned to the ordinary constant V/F characteristics.
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