| 摘要 |
PURPOSE:To prevent a motor with power source by means of a three-phase power supply from reversing and causing an unforeseen accident by comparing a phase difference value between two waveform shaping signals obtained by shaping two-phase voltage waveforms taken out from power given to the motor with a normal phase difference value. CONSTITUTION:A waveform shaping circuit 21 gives square-waved signals 21A, 21B obtained by shaping two-phase voltage waveforms of a given detection input l2C to the input-output port 24 of CPU 25. Then, the phase difference value between the square-wave signals 21A and 21B is processed by comparison operation by means of a reference value and CPU25. When the phase difference value is within the range of the reference value, a normal signal 25A is given to an operation controller 400 and to a closing circuit 12 so that three-phase power 300 is given as driving power l2B to a motor 200. Also, when the phase difference value is outside the range of the reference value, a phase abnormal signal 25B is given to the phase-changing circuit 11 of an input controller 1 so that predetermined phases are switched and the driving power is changed to positive three phases. |
