Three-phase alternating current is a form of transmission of electrical energy, referred to as three-phase electricity. The three-phase AC power supply is a power supply composed of three AC potentials having the same frequency, equal amplitude, and phase difference of 120°.
Three-phase alternating current has many uses, and most of the AC electrical equipment in the industry, such as electric motors, use three-phase alternating current.
The three-phase alternator has higher output power than the single-phase alternator of the same size; in terms of power transmission, the three-phase power supply system also saves material compared with the single-phase power supply system; from the perspective of power consumption, the three-phase AC motor widely used in production Compared with other types of AC motors, DC motors have the advantages of excellent performance, simple structure, and low price.
Three-phase electric load connection
It is divided into a delta connection (symbol △) and a star connection (also known as a Y-connection, symbol Y).
1. Connect the tail end of each load to the neutral line N, and each load head end is connected to the phase line to form a star connection. In electrical engineering, we connect the load into a single-phase 220V voltage, such as a 220V illuminator, a single-phase motor, a single-phase electric furnace, and so on. The electrical equipment is connected to the circuit by star connection. It should be considered to evenly distribute the equipment on the phase line of the three-phase power supply to maintain the three-phase load balance distribution. If this is not the case, the circuit breaker may trip open to indicate that the load is unbalanced, and the first-time electrician should pay attention to this.
2. The so-called triangular (△) connection of the load is to connect the head of the phase in the three-phase load to the tail of the other phase. The load of this connection, the three phase currents, and the three line currents are three-phase symmetrical currents of equal value and phase difference of 120°, and the the line current is equal to 
the phase current.
