Three-phase alternating current is a form of electrical energy transmission, simply referred to as three-phase electricity. A three-phase alternating current power supply consists of three alternating electromotive forces with the same frequency, equal amplitude, and phases differing sequentially by 120°.
Three-phase alternating current has many applications. Most AC electrical equipment in industry, such as motors, uses three-phase alternating current. In daily life, however, single-phase power is more commonly used, also known as lighting electricity. When lighting electricity is used for power supply, one phase of the three-phase electricity is used to supply power to electrical equipment, such as household appliances, while the other wire is the fourth wire in the three-phase four-wire system, that is, the neutral wire, which is drawn from the neutral point of the three-phase electricity.
The alternating current generated, transmitted, and distributed by power plants and power grids is three-phase alternating current. This is because three-phase alternating current has many advantages. In terms of power generation equipment, a three-phase alternator outputs more power than a single-phase alternator of the same size; in terms of power transmission, the three-phase power supply system also saves materials compared to the single-phase power supply system; in terms of power consumption, the three-phase AC motors widely used in production have advantages such as excellent performance, simple structure, and low price compared to DC motors and other types of AC motors.
Differences between three-phase power supply and single-phase power supply:
1. In a single-phase sinusoidal AC circuit, the single-phase AC voltage, single-phase AC current, and single-phase AC electromotive force all change according to the sinusoidal law. It can also be vividly said that three-phase alternating current is the overall effect of three single-phase alternating currents on the circuit.
2. Three-phase alternating current has many advantages: manufacturing three-phase alternators and transformers saves more materials than single-phase ones, and they have a simple structure and excellent performance; under the same conditions, when transmitting the same amount of power, three-phase transmission lines save 25% of non-ferrous metals compared to single-phase transmission lines, and there is also less power loss; three-phase motors have better performance than single-phase motors, and so on.
