| 摘要 |
PURPOSE:To make high power factor operation possible making the best use of the feature of asymmertrical control, without raising the secondary voltage of a transformer, even in the case of driving a synchronous motor by low voltage, by changing the value of constant voltage along with changing beta limit according to the amplitude of phase voltage. CONSTITUTION:Low-voltage output voltage EVL at below the speed N(Valpha) of a synchronous motor and output voltage EUH at speeds exceeding N(Valpha) in time of a constant voltage Valpha are shown by the figures. By these characteristics, in the low-voltage region, it becomes possible for beta limit to cancel sufficiently by enlarging the beta limit and by suppressing asymmetrical fixed-side voltage low, as inversion operation is done during half-cycle periods. And in the high-voltage region, it becomes possible to commutate safely by making the beta limit smaller and the symmetrical fixed-side voltage higher, as the inversion operation region becomes narrower and current value commutable in this region becomes smaller compared to a maximum peak value. Incidentally, the beta limit can also be changed continuously corresponding to an output voltage reference or speed signal. |
