The utility model relates to a two return circuit interchange changers. Include microcontroller circuit, three -phase electricity acquisition circuit, communication interface circuit, be used for forwhole changer power supply circuit, microcontroller circuit communicates with the host computer through communication interface circuit, and microcontroller circuit still passes through three -phase electricity acquisition circuit gathers the three -phase electrical parameter, three -phase electricity acquisition circuit is including the strong and weak electrical isolation module that is used forrealizing strong and weak electrical isolation, three -phase electricity signal acquisition and the metering modules who is used for realizing three -phase electricity signal acquisition and calculation. The utility model discloses can monitor two three -phase ways, and the monitoring that has multiple parameter, still have the RS485 communication interface that makes progress, support remote maintenance.