| 摘要 |
PURPOSE:To improve a line gradient upward moving characteristic by constantly controlling the ratio of a voltage applied to a motor to a frequency so that the maximum current of a motor current becomes substantially equal to that under normal starting and accelerating conditions when started at the line having a gradient. CONSTITUTION:A reference slip frequency FSO and a correction slip frequency FS1 in response to a current pattern IC based on a response load signal VL are added to produce a slip frequency FS, and an inverter output frequency F is determined by the slip frequency FS and a rotating frequency FR. A modulation pulse mode calculator 37 sets a modulation pulse mode N to approximate to a sinusoidal wave. A modulation factor calculator 38 calculates a modulation factor AL=K(aF+b)/EC by the output frequency F and a filter capacitor voltage EC. When a gradient UP command HAC is inputted, a constant K is altered so that the maximum value of a motor current becomes substantially equal to that under normal starting and accelerating conditions. |
