| 摘要 |
PURPOSE:To simplify the structure of an inverter and to increase the lifetime of the inverter by effectively and rapidly decelerating an AC motor to be controlled to the rotating speed less than a resonance point when the output from an inverter main circuit is stopped. CONSTITUTION:When an overcurrent flows in a line, the base signals of all transistors Tr11-Tr32 are interrupted upon reception of a signal from a current detector 11 which detects the overcurrent, the transistors Tr11, Tr22 are then fired. Then the transistors Tr21, Tr32 are then fired after the prescribed period of time is elapsed, the transistors Tr31, Tr12 are then fired after the prescribed period of time is further elapsed, these operations are then repeated, thereby forming always a DC brake circuit of an AC motor 8. In this manner, the motor 8 is rapidly decelerated to the rotating speed less than the resonance point. |
