| 摘要 |
PURPOSE:To enable smooth transition from the constant current control zone to the current limit step control zone by transiting a motor to field weakening control when the control phase angle of each semiconductor switch element in a group of control rectifier goes to zero and the current of a DC motor drops below a set value. CONSTITUTION:A comparator 23 provides a difference signal between a current set value 1p corresponding to a notch signal fed from a trunk controller 20 and the current Ia of DC motors 5, 6 to a regulator 24. The regulator 24 controls semiconductor switching elements 13, 14 according to an input signal. When a field weakening command is provided, the current set value 1p exceeds over the current Ia and when all the control phase angle of all semiconductor switching elements 13, 14 in the control rectifier groups 1U-4U is commanded to zero, a signal is outputted from an AND gate 30. Consequently, the contact 33a of a contactor/controller 33 is closed and a field weakening resistor 34 is inserted. |
