| 摘要 |
PROBLEM TO BE SOLVED: To provide a circuit for preventing the open-phase or reverse-phase operation of a three-phase motor which can surely prevent the open-phase and reverse-phase operation of the motor, whether it is at start of operation of the three-phase motor or it is in operation. SOLUTION: In case that at least either contact 31 or 41 is in open condition between the contact 31 of a first reverse phase preventive relay 30 connected in the specified phase order of the supply circuit of a power source 1 and the second reverse phase preventive relay 40 connected in the specified phase order where one phase is slid from the first reverse phase preventive relay 30 to the supply circuit of the power source, the phase order of the supply power source is switched by a normal phase reverse phase switching relay circuit 20. Furthermore, in case that at least either of each contact 31 and 41 gets in open condition or gets in open condition during operation of a motor 2, the open-phase operation or the reverse-phase operation of the motor 2 can be surely prevented whether it is at start of operation or in operation by actuating an alarm 60. |
