| 摘要 |
PURPOSE:To smoothly shift a phase current to a trapezoidal shape in a low speed range and to a sinusoidal wave shape in middle and high speed range by inserting a reactor during a neutral unblanking period between a power converter and the motor. CONSTITUTION:A reactor 6 is inserted and connected during neutral unblanking period for connecting the neutral point MU of cycloconverters 1-3 and the neutral point MM of a motor winding. Since the impedance given by the reactor 6 is low in a motor low speed range, near a shortcircuit state between the neutral points MU and MM, and a zero phase current is flowed without limit, a phase current flowed to the motor becomes trapezoidal shape. On the other hand, as the speed rises, the impedance of the reactor 6 increases, the zero phase current is gradually limited, the phase current is decreased in the trapezoidal shape to approach to the sinusoidal wave, and becomes apparently not connected between the neutral points in the high speed range, and the phase current becomes sinusoidal waveform. |
