| 摘要 |
PURPOSE:To prevent the current in the winding of a motor from decreasing abruptly, by turning a switching element ON/OFF to limit the curent upon detection of an overcurrent. CONSTITUTION:Overcurrent in a main circuit 15 is detected by a current detector 21 and a current limit signal is delivered from an overcurrent decision circuit 22. Consequently, a control circuit 18 turns all transistors 14a-14c on the positive side ON and turns all transistors 14d-14f on the negative side OFF. Since the current in the windings 20u, 20v, 20w of a three-phase induction motor 19 circulates through any one of the transistors 14a-14c on the positive side being turned ON or any one of the flywheel diodes 16a-16c therefor and does not flow through a DC power supply 11, the current in the windings 20u, 20v, 20w can be prevented from decreasing abruptly. |
