| 摘要 |
PURPOSE:To stop an inverter and protect the load side, by using a notch filter, and by detecting the abnormal state of the distortion factor of output voltage. CONSTITUTION:An inverter 1 of a modified twelve-phase zigzag connection supplies power to a load 3 via an AC filter circuit 2. In a protecting circuit, the output voltage to the load is detected by a transformer 4, and the detected voltage is full-wave-rectified by an absolute value circuit 7 via an interface circuit 5 and a notch filter circuit 6, and deprived of ripples and smoothed by a smoothing circuit 8. Then, the output of the smoothing circuit 8 and a set value 9 are compared with each other by a comparator 10, the output of which is send to a protecting logic circuit 11. This logic circuit 11 outputs an inverter stop command 12, and reset by a reset circuit 13. Then, the frequency characteristic of the notch filter circuit 6 is selected so that a minimum gain may occur at the frequency of the fundamental wave component of the output voltage of the twelve-phase inverter 1, and the output of the notch filter circuit 6 includes components other than the fundamental-wave component, so that the load 3 is protected.
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