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In general, we call the process of converting DC power into AC power an inverter, the circuit that completes the inverter function is called an inverter circuit, and the device that realizes the inverter process is called an inverter device or an inverter.
Why are common grid-connected inverters only divided into single-phase and three-phase? In fact, the main reason is the type of grid connected to the inverter.
First of all, let's understand, what is "phase"? "Phase" refers to the three-phase live wire (A/B/C or L1/L2/L3), and the transformer generally outputs three live wires and one neutral wire (N wire) , and some will also lead to a ground wire (PE).

So what are single-phase, two-phase, and three-phase? What are the voltages of the various types of electricity used in daily life?

▌Single phase
It consists of a live wire and a neutral wire. "Single" refers to any one of the three phases. The standard voltage between A-N, B-N, and C-N is 220V.
▌two-phase
Also known as two-phase, any two-phase live wire (A-B, B-C, A-C) in the three-phase composition, the voltage is 380V, and it is not often seen in daily life, such as an electric welding machine is an electrical appliance that uses two live wires of 380V.
▌Three-phase
It is three live wires, represented by ABC. If it is only a three-phase voltage, it is 380V, also known as a three-phase triangle; if there is a neutral line in addition to the three live wires, the voltage will have 220V and 380V, which is a three-phase star. shape connection.
The phase angles between the three phases B and C are 120 degrees each other, which is symmetrical in electrical space. 380V is the line voltage and 220V is the phase voltage. The calculation formula between the two is as follows. The inverter will also have 400V/230V, which is also calculated in the same way.
When installing a three-phase inverter, you often hear three-phase four-wire and three-phase five-wire. After talking about "phase", let's talk about "wire". The common types are as follows:
Three live wires + one neutral wire, mainly 380V/220V low-voltage lines, use the working neutral wire N as the zero protection wire PE, which can be called the protective neutral wire, represented by NPE, and is suitable for power consumption where the three-phase load is basically balanced place.
Three live wires + one neutral wire + one ground wire, a power supply system that strictly separates the working zero wire N and the dedicated protection wire PE, is used in places with high safety requirements and grounding of electrical equipment.
Generally, single-phase grid-connected inverters are connected to single-phase two-wire and single-phase three-wire grid lines.
Three-phase grid-connected inverters are integrated into three-phase four-wire and three-phase five-wire grid lines.
There is also a medium and high voltage grid-connected three-phase inverter, such as 480V/800V grid-connected, which needs to add a corresponding step-up transformer to connect to the three-phase three-wire grid (above 10KV).