What is single-phase current

The single-phase current, or single-phase electric current, is one that only travels in one direction and through a single conductor. The single-phase system is the most commonly used for the distribution of lighting, small electric motors and heating. It is a system of production, distribution and consumption of electrical energy formed by a single alternating current or phase. This current, unlike triphasic, has a much lower voltage. This is due to the fact that the three-phase current has 3 phases and 3 alternating currents, which gives rise to an increase in it. Next, we analyze in more detail what single-phase current, or single-phase alternating current, is, what its characteristics are, its uses and the main differences between the two most used types of alternating current: Single-phase current and triphasic current.

What is single phase current?

Single-phase current, or single-phase electrical current, is the type of alternating current that reaches the house. All homes are designed with a single-phase AC circuit—some older homes excluded. But what exactly does this mean? If we base ourselves on the installation of the home’s single-phase alternating current circuit, what happens is that the single-phase current reaches the home through the R phase cable —the cable that is brown—. The current then returns through a neutral wire that completes the circuit, known as phase n cable —or what is the same, the blue cable—. In this type of single-phase alternating current circuit, the neutral wire has a zero potential, this is so because it does not have any electrical charge or voltage. On the other hand, we must not forget the ground wire, essential to avoid overloads and complications due to the malfunction of any device. This wire is colored green and, in some cases, yellow.

Now, to be clearer about what single-phase current, or single-phase alternating current is, it is essential to make clear what the definition of alternating current is. Alternating current is one in which the magnitude and direction vary cyclically. The most common form of oscillation in alternating current is sinusoidal., thanks to which a much more efficient transmission is achieved than otherwise. The fundamental advantage of alternating current is how easy it is to raise the voltage. For this, only one transformer is needed. Contrary to what happens with its opposite, direct current, in order to raise its voltage it is necessary to use dynamos seriously, which is not very practical.

Characteristics of single-phase current

Once we have a more than approximate idea of ​​what single-phase current is, we now go on to analyze some of its most outstanding characteristics. These are:

• Voltage with identical variations: Because the single-phase alternating current circuit is made up of a single phase, the voltage variation always varies in the same way. The same does not happen in the case of three-phase current, where there are 3 different phases through which the current flows with a phase shift of 120º.
• voltage values: The voltage values ​​usually range between 110 and 230V.
• Variations in each countryNote: While the permitted voltage in Spain is 230V, this may vary in other countries. Examples of them are Ecuador and El Salvador, with 120V; Egypt, with 220V; Cuba, with 110 V, etc.

Uses of single-phase current

The uses of single-phase current, or single-phase alternating current, are practically 3, as we mentioned in the introduction. These are:

• Lightning: Above all, for the home lighting system.
• Heating: The single-phase electric current is also used for heating homes and for appliances or devices that we can have in the home.
• small engines: Another less frequent use of single-phase alternating current is for small motors. However, because a single-phase supply connected to an electric motor does not produce a rotating magnetic field, additional circuitry is often required to achieve its starting.

Difference Between Single Phase and Three Phase Current

Although both use an alternating current system, the differences between the two are many. Next, we analyze what are the main differences between single-phase and three-phase current:

• voltage difference: While the single-phase current usually has a voltage of 110 to 230V, the three-phase current exceeds the value by far, reaching about 380V.
• Different system or circuit: The wiring of both AC systems varies from each other. In the case of single-phase current we find a 3-wire installation, as explained above, while in three-phase current the wiring consists of the following circuit made up of 5 cables:
  • black wire: For phase 1.
  • brown wire: For phase 2.
  • gray wire: For phase 3.
  • blue wire: For neutral.
  • green or yellow wire: For grounding.
• Price: Three-phase current can also be used in home installations, especially when we lack power due to the number of high-consumption devices and appliances used. In that case, the three-phase current is of great help because it has more power. Now, this supposes an increase in the final price of our bill, while the single-phase current is cheaper. It is essential, in the event that the installation of the house is done with a three-phase current circuit, that appliances prepared for it are used.
• Power: The power required by the three-phase current so that the electrical appliances that work with it can work must be greater than 14.45 kW, while in the case of single-phase electric current installations, this is much lower.
• Use: In general, the use of three-phase current is usually associated with large warehouses or factories. The use of single-phase alternating current is intended for homes.

These are only the concepts of single-phase current.