5. AC cabling
5.1 Power generation
The generator in a power station generates 3 phase electricity. Each of these 3 phases have an alternating voltage of 230 Volt (or a different voltage, depending on the country). The voltage alternates at a frequency of 50 (or 60) Hz. And because the coils in the generator are rotating, there is a 120°-degree phase shift between each phase.
The 3 coils are connected to each other and create a triple circuit, a so-called star configuration. A single coil (phase) has a potential of 230Vac. And a second potential level is created between two coils. Due to the 120° phase shift the potential is 400 Vac.
To be able to use the phases separately the common point (star point) is connected to a conductor called “Neutral”. Between the neutral and one of the phases a voltage of 230 Volt exists. The Neutral conductor is a conductor that can be used by all 3 phases and can be used in 3 separate electrical circuits. The star point acts as a neutral in electrical house installations. The function of the neutral conductor is to enable separate use of each phase and each phase can be used as an individual 230 Volt AC supply. The neutral is also connected to a metal spike driven into the ground, the so-called earth spike. In this way the potential of the earth equals 0 Volt. This connection is called earth. A 3-phase load, like a 3-phase electric motor, uses electricity from all 3 phases. The neutral does not have a function because the 3 electrical circuits will keep each other balanced. Only if one of the phases consumes more load than the others, the neutral will start to conduct current. This current is called the “compensating or equalizing current”.
When setting up 3 phase inverter/chargers they will need to be set up in a star configuration. They need to have a common Neutral. Delta is not allowed. The load they run can be a load in Delta configuration. Unequal loading is not an issue if the inverter/chargers run in inverting mode, but it might be an issue if they un in pass-through mode and they are connected to a generator that is unable to deal with an unbalanced load. 5.2 Distribution networks There are different ways in which power is distributed to the consumer. And different ways in how the consumer system is connected. All networks supply the 3 phases, but the way Neutral and Earth are bonded varies. TN-S network • The generator star point is connected to Neutral and to Earth. • The phases, Neutral and Earth are distributed. • The consumer uses the supplied phases Neutral and Earth. • Neutral and Earth are not connected to each other.
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