Physics trivia

# Single-phase, two-phase and three-phase systems

Single, two and three-phase systems are installed according to the type of establishment and the amount of electrical equipment.

The energy supply for the numerous residential, commercial and industrial establishments can be done through single-phase, two-phase or three-phase systems. The use of each transmission system depends on the type of establishment that will receive the electricity and the total power of the electrical equipment connected to the grid.

single-phase system

In the single-phase system, the network is built with two wires: one phase and one neutral. The maximum electrical voltage that can be supplied by this system is 127 V. Single-phase networks are installed only when the sum of the powers of all the equipment in a residence reaches a maximum value of 8 kW (8000 watts).

two-phase system

The two-phase system is characterized by the existence of three wires between the electrical network and the establishment that will receive energy. The electrical voltage capacity is 127 V or 220 V. This type of connection is used only in rural areas, where the amount of electrical equipment is not as large as in urban areas. Two-phase systems are used for powers from 12000 W to 25000 W.

In a three-phase system, the electrical network consists of four wires: three phases and a neutral. The electrical voltages generated are 127 V or 220 V and can handle powers from 25000 W to 75000 W. The three-phase installation is the most suitable for homes that have electrical equipment whose sum of powers exceeds 8000 W, as well as for industries and the business.

1. Prevents untimely power outages;

2. It uses less copper and aluminum to provide the same power as a single-phase system;

3. Total power is never zero;

4. Three-phase motors are smaller than single-phase motors of the same power.

Three-phase system protection

The protection of a three-phase installation is carried out with the aid of a three-pole thermomagnetic circuit breaker. Each phase can be connected to a circuit breaker pole and serve a different sector of a residence, for example. If an overload occurs in one of the sectors of the house, the circuit breaker will be turned off, but the power supply to the other rooms will not be affected.