| 摘要 |
PURPOSE:To prevent the occurrence of a surge current for making of a phase advance capacitor by allowing the switch operation of capacitor making to coincide with a maximum point of the voltage. CONSTITUTION:An output voltage expressed with a sine waveform Esintheta is obtained at a point A in the secondary side of a transformer 5 whose primary side is connected to a bus 1. This sine wave has the same phase as the frequency on the bus 1, and its integral value coincides with a 90 deg. phase delayed waveform a Esintheta. If a maximum voltage point of the integral value is detected, a point of the highest voltage is detected by the zero point of the integral value because said maximum voltage point coincides with the point of the highest voltage of the bus 1. Consequently, said sine wave is integrated by a mirror type integrator 6 to obtain a waveform Ecostheta, and this waveform is inputted to a comparator 7 whose comparison reference voltage is set to zero, and the output is differentiated by a differentiating circuit 8, and its positive-side pulse is inputted to one input terminal of a NAND circuit 9, and the output of a discriminator 4 is inputted to the other input terminal. |
