The difference between single-phase and three-phase voltage

The difference between single-phase and three-phase voltage

The difference between single-phase and three-phase voltage

The difference between single-phase and three-phase voltage, simple and composed voltage it is basically in their value.

To explain the difference between single-phase and three-phase first you need to understand that the composed voltage is √3 times bigger than the simple voltage, in other words, V(composed)=V(simple) x √3  (approximately 1,732).  This difference can be identified with a voltmeter. For the composed voltage we measure the voltage between the two phases, and for the simple voltage, we measure the voltage between the phase and the neutral.

An alternator that provides single-phase voltage will have the windings connected in a way that it will be available for the customer's installations with one phase and the neutral. In general, for most markets, the single-phase voltage value is 230V. However, in Latin America, it is very common for the single-phase to vary between 115V, 127V, 220V, among others. Equipment’s with illumination, microwaves, automatic gates, portable welding devices, among others, are supplied with single-phase voltage.

In the case of an alternator that provides three-phase, it will have winding connected so that the customer's installation has three-phase and neutral. In a great part of the market, the three-phase value is 400V between phases and 230V between phase and neutral. As well as the single-phase, in Latin America, it is common to exist three-phase voltage that varies between 208V, 220V, 380V, among others. Equipment’s with electric engines, pumping systems of great size, elevators, large compressors are supplied with three-phase voltage.

In the electric power system (electric grid) from the generation up to the distribution, the system operation is performed with three-phase voltage, whether in the hydraulics, Eolic parks, solar or thermal plants.

Apart from the loss reduction by physical means through the energy transmission, the main reason to work with the three-phase voltage is the electrical power gain. The electrical power in a system that works with three-phase voltage is three times bigger than the same system working with single-phase, in other words, P (three-phase voltage) = 3 x P (single-phase voltage). Overall, the residencies, are supplied with single-phase voltage and the industry with three-phase voltage.

Therefore, if you need equipments with more power to perform hard tasks, such as the loading and unloading containers, for example, it is inevitable to not consider equipments with three-phase voltage. When we are specifying the genset features to a customer, what determines the choice between single-phase and three-phase are the loads that the genset will have to supply. As expected, for the loads that need the three-phase voltage, the three-phase genset should be specified. However, these gensets can also provide power to single-phase loads, and in this case,  it is necessary to be have under consideration the balance of the loads between phases.

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