| 摘要 |
PURPOSE:To improve the reliability by comparing output voltage from an average circuit with voltage obtained by dividing output voltage from a peak value detection circuit and, if open phase is detected from the difference in voltage waveform between the terminals of three phases, opening a circuit. CONSTITUTION:In the case of phase interruption of a motor, the form of the full wave of voltage is transmitted from a rectification circuit 3, equalized in an averaging circuit 6, and entered to a comparison circuit 8. The form of the full wave is also transmitted to a peak value detection circuit 7, which detects a peak value detection waveform and transmits it to the comparison circuit 8 after voltage division. The comparison circuit 8 compares the average waveform with threshold voltage as the reference value obtained by voltage division and, if the value of the average waveform is under the reference value, transmits the signal thereof to a thyristor 10. The thyristor 10 allows a current to pass through a trip coil 11 according to the signal to operate the trip coil 11 and open a circuit. |
