Three wire circuit

Three-wire circuit when connecting the phases of the receiver with a star without a neutral wire is called three-wire. Only symmetric receivers (three-phase electric motors, electric furnaces) can be included in such a circuit.




If the receiver is asymmetrical, then an offset voltage appears between the neutral points of the generator and the receiver.
This voltage can be determined by the method of two nodes


The voltages on the receiver phases are unequal to the voltages on the generator phases


Those. when the resistance changes in one phase, all phase currents and voltages will change, i.e. The receiver’s phase voltages are not equal to the source phase voltages due to the neutral displacement, therefore, the currents will not be equal either
Asymmetric load is, for example, three-phase three-electrode arc furnaces.
The voltages on the phases of the receiver are not equal to the voltages on the phases of the generator.
When the resistance in one phase changes, all phase currents and voltages will change, i.e. The phase U of the receiver is not equal to the phase voltages of the source due to the displacement of the neutral.

In the case of a symmetric receiver, it suffices to determine the current in one phase