| 摘要 |
PURPOSE:To improve the reliability of a voltage inverter by limiting the output current of an inverter to a value lower than the set value even in a regenerative mode of a load motor or in the transient state at the time of switching from a commercial power source to an inverter power source. CONSTITUTION:The output current of an inverter bridge 2 is detected by current detectors 4A, 4B, is converted into a DC via a rectifier 17, and is inputted to a level detector 16A. When the detected value becomes higher than the set level, the detector 16A closes AND gates 13-15, thereby interrupting drive signals of transistors 24, 26, 22. As a result, the power supply from an inverter bridge 2 to a DC power source 1 is stopped. Even if the transistors 24, 26, 22 are interrupted, a circulating current flowed between the transistors 21, 23, 25 and diodes 31, 33 by the counterelectromotive force of a load motor 3. When the level detector 16B operates, AND gates 18, 19, 20 are closed to interrupt the transistors 21, 23, 25, and a current from a load side is abruptly attenuated. |
