Conservation manner null of electric current forma invar -

摘要

PURPOSE:To eliminate DC short-circuit condition, by a method wherein an intermediate condition, in which a non-conduction condition is produced simultaneously with the switching of a conducting condition, is provided in a phase, in which DC short-circuit is estimated, for only a period of time wherein a current, conducted at present, is intercepted. CONSTITUTION:A current type inverter rectifies a power from an AC source 1 by a converter 2, driven by a gate circuit 7, and converts it into the alternated current having a predetermined frequency and magnitude by an inverter 4 driven by the gate circuit 8 to supply it to a motor 5. The control unit 9 of the inverter is constituted of an one-tip micro-computer and operates an inverter frequency command omega0, the phase angle command phi0 of an output current and a DC current command (i10) by a vector operating and processing unit 97 from the speed command omega0 of the motor 5 and the feedback speed omegar of a speed detector 16. The phase command alpha0 of the converter 2 is op.rated by a current control operating unit 93 and the conducting conditions of respective elements are obtained by an output pattern determining unit 94; then, the output of the inverter may be effected.