In accordance with an example embodiment of the invention, a three-phase power control device is configured to synchronize firing thyristor or SCR sets in consecutive combinations of two of the three phases, to supply current to consecutive combinations of two of the three loads in a three-phase load configuration, to determine real branch impedance of each load from three combinations of two supplied loads, without need of any electrical neutral reference.

A method and system for operating an inverter, which has a terminal with four conductor connectors for connection of the inverter to three outer conductors and to a neutral conductor of an AC voltage grid is disclosed. The method includes determining a connection configuration of the inverter to the AC voltage grid by actuating switching elements of a bridge circuit of the inverter to generate a zero-phase sequence system having a zero-phase sequence system current, and measuring and evaluating output currents of the inverter with respect to the zero-phase sequence system current. The method also includes identifying a presence of a connection of the neutral conductor to a conductor connector provided for connection to the neutral conductor when the zero-phase sequence system current exceeds a prescribed threshold value and identifying that the neutral conductor is not connected to the conductor connector provided for connection to the neutral conductor otherwise.

A method and system for operating an inverter, which has a terminal with four conductor connectors for connection of the inverter to three outer conductors and to a neutral conductor of an AC voltage grid is disclosed. The method includes determining a connection configuration of the inverter to the AC voltage grid by actuating switching elements of a bridge circuit of the inverter to generate a zero-phase sequence system having a zero-phase sequence system current, and measuring and evaluating output currents of the inverter with respect to the zero-phase sequence system current. The method also includes identifying a presence of a connection of the neutral conductor to a conductor connector provided for connection to the neutral conductor when the zero-phase sequence system current exceeds a prescribed threshold value and identifying that the neutral conductor is not connected to the conductor connector provided for connection to the neutral conductor otherwise.

System, apparatus and methods are provided for identifying a phase loss condition in a motor drive. In one example, a power conversion system includes an active rectifier, a switching inverter, and a controller. The controller is operative to generate rectifier switching control signals to operate the rectifier, measure AC input voltage signals and determine grid current signals. If the rectifier circuit is not in a switching mode, the controller identifies a suspected AC input phase loss condition if two of the AC input voltage signals are in phase with one another. If the rectifier is in the switching mode, the controller identifies a suspected AC input phase loss condition if the absolute value of the sum of two of the grid current signals is less than a predetermined non-zero threshold.

A system for a three-phase electric power system includes a plurality of voltage sensors sensing three-phase voltages of the three-phase electric power system; a plurality of current sensors sensing three-phase currents of the three-phase electric power system; and a number of analog-to-digital converters converting the sensed three-phase voltages and the sensed three-phase currents of the three-phase electric power system to corresponding digital values. A processor calculates from the corresponding digital values at least two phase angles between voltage and current for at least two of three phases of the three-phase electric power system, diagnoses polarities and phase associations for at least two of the current sensors based on, for each of the at least two current sensors, a predetermined wiring configuration of the three-phase electric power system and a corresponding one of the at least two phase angles being within a corresponding predetermined angular range, and outputs corresponding diagnosis results.

A method and system for operating an inverter, which has a terminal with four conductor connectors for connection of the inverter to three outer conductors and to a neutral conductor of an AC voltage grid is disclosed. The method includes determining a connection configuration of the inverter to the AC voltage grid by actuating switching elements of a bridge circuit of the inverter to generate a zero-phase sequence system having a zero-phase sequence system current, and measuring and evaluating output currents of the inverter with respect to the zero-phase sequence system current. The method also includes identifying a presence of a connection of the neutral conductor to a conductor connector provided for connection to the neutral conductor when the zero-phase sequence system current exceeds a prescribed threshold value and identifying that the neutral conductor is not connected to the conductor connector provided for connection to the neutral conductor otherwise.

The open-phase condition of a standby power transformer is detected by monitoring functions of the phase currents. The functions have parameters calculated based on reference currents, which constitute a fingerprint when all the phases are connected.

The open-phase condition of a standby power transformer is detected by monitoring functions of the phase currents. The functions have parameters calculated based on reference currents, which constitute a fingerprint when all the phases are connected.

Disclosed are a three-phase wiring detection device and a coincidence phase detection method. The three-phase wiring detection device and the coincidence phase detection method compare a power factor relationship between a three-phase voltage and a three-phase current, and determines whether a coincidence phase is coincident between the three-phase voltage and the three-phase current, thereby checking whether the coincidence phase is accurately coincident. Therefore, whether the coincidence phase is coincident between the three-phase voltage and the three-phase current can be checked, and a function of a reverse phase detector and a function of a coincidence phase checker can be implemented. Also, the three-phase voltage and the three-phase current can be accurately detected.

Disclosed are a three-phase wiring detection device and a coincidence phase detection method. The three-phase wiring detection device and the coincidence phase detection method compare a power factor relationship between a three-phase voltage and a three-phase current, and determines whether a coincidence phase is coincident between the three-phase voltage and the three-phase current, thereby checking whether the coincidence phase is accurately coincident. Therefore, whether the coincidence phase is coincident between the three-phase voltage and the three-phase current can be checked, and a function of a reverse phase detector and a function of a coincidence phase checker can be implemented. Also, the three-phase voltage and the three-phase current can be accurately detected.