| 摘要 |
PURPOSE:To make a stabilized operation, with a hunting state prevented, by means of correcting a frequency of the inverter so that the detected value of conduction delay time may coincide with the target value of conduction delay time determined from a main circuit condition and an operating condition. CONSTITUTION:When an AC motor 30 is driven by a converter 28 and a current control type inveter 29, a conduction delay time is detected by a conduction delay detector 44 from a gate signal of the inverter 29 and a leading edge of load current. In accordance with a deviation between the above detected value and the target value of conduction delay time, obtained by a gain adjustment of voltage command value from a function generator 38 in a function generator 46, a correction is applied to a frequency command voltage from a speed command device 37. Consequently, if becoming longer the conduction delay time, an operation tends to raise a frequency, with a time, for commutation overlapping period to start, coming to be earlier, causing a suppression to work for a fluctuation of conduction delay time, thus capable of raising a frequency stably operable. |
