We usually use three-phase four-wire systems with a phase voltage of only 220V. Industrial motors typically have a rated voltage of 380V, so the line voltage is also 380V, meaning there are two live wires. Your question is difficult to explain. Phase voltage is the voltage between the live wire and the neutral wire. Line voltage is the voltage between the two live wires. Three-phase voltage is also 380V, and industrial motors generally have a rated voltage of 380V, usually connected in a delta configuration. That is, there are only three phase wires.
Home electricity is two-phase, 220 volts, while industrial electricity is generally three-phase, 380 volts. Three-phase industrial electricity has several advantages: two-phase electricity cannot start a motor (it requires a starting capacitor), while three-phase electricity can start a motor and even change the direction of rotation. The higher voltage of three-phase electricity helps prevent overheating from excessive current when using high-power appliances.
Three-phase electricity: Let me explain in more detail. We know that when a coil rotates in a magnetic field, the conductor cutting the magnetic field lines generates an induced electromotive force (EMF), whose variation can be represented by a sine curve. If we take three coils and position them 120 degrees apart in space, and the three coils still rotate at the same speed in the magnetic field, they will definitely induce three EMFs with the same frequency. Since the three coils are 120 degrees apart in space, the generated current also exhibits a three-phase sinusoidal variation, called three-phase sinusoidal alternating current. Industrial electricity uses three-phase electricity, such as three-phase AC motors.
Simply put, two-phase electricity consists of one live wire and one neutral wire, while three-phase four-wire electricity consists of three live wires and one neutral wire. In three-phase electricity, the voltage between live wires is 380V, but the voltage between any live wire and the neutral wire is 220V. This means that we can use any live wire and neutral wire from any three-phase power supply for our home electricity needs.
