Phase loss detection circuit for three-phase AC power supply

摘要

PROBLEM TO BE SOLVED: To provide an open-phase detection circuit of three-phase AC power supply capable of stopping the system reliably when open-phase is detected, by simple configuration.SOLUTION: An open-phase detection circuit 10 includes an AC/DC converter 11 connected with a three-phase AC power supply 1 and actuating a single-phase load 2, and a relay coil 12A connecting with the three-phase AC power supply 1. The relay contact 12B of an AC relay 12 is provided in the circuit of single-phase load 2. In the open-phase detection circuit 10, the AC/DC converter 11 is not electrified when the first phase (T phase) of the three-phase AC power supply 1 is out of phase, the relay coil 12A is not electrified when the second phase (R phase) of the three-phase AC power supply 1 is out of phase, and the AC/DC converter 11 and relay coil 12A are connected in series when the third phase (S phase) of the three-phase AC power supply 1 is out of phase.SELECTED DRAWING: Figure 1