Inverter main classification

Inverters are primarily categorized into two main types: sine wave inverters and square wave inverters. Sine wave inverters produce a clean, smooth alternating current that closely resembles the power supplied by the electrical grid. This high-quality output is free from electromagnetic interference, making it ideal for sensitive electronics. On the other hand, square wave inverters generate a less refined, square-shaped AC waveform. This type of waveform can cause instability in connected devices, as the transition between positive and negative peaks happens abruptly, leading to potential damage or performance issues. Additionally, square wave inverters have limited load capacity—typically only 40-60% of their rated load—and cannot support inductive loads such as motors or transformers. If the load is too large, the third harmonic present in the square wave can increase the capacitive current flowing through the system, potentially damaging the capacitors in the connected equipment.

To address these limitations, quasi-sine wave (or modified sine wave) inverters were developed. These inverters produce a waveform that is closer to a sine wave, with a smoother transition between the positive and negative peaks. While this improves performance compared to traditional square wave inverters, the waveform is still composed of straight-line segments, making it less continuous and still classified as a form of square wave. In summary, sine wave inverters provide superior power quality, capable of handling any type of load, but they come with higher costs due to more complex technology. Quasi-sine wave inverters offer a good balance of efficiency, affordability, and performance, making them the most popular choice in today’s market. Square wave inverters, based on older multivibrator technology from the 1950s, are gradually being phased out due to their poor performance and reliability.

Inverters can also be classified based on their power source. For example, coal-electric inverters, solar inverters, wind energy inverters, and nuclear power inverters each serve different applications. Depending on their purpose, they may be either independent control inverters or grid-connected inverters. When operating, inverters consume some of the input power, which means the output power is always slightly less than the input. The efficiency of an inverter is calculated as the ratio of output power to input power. For instance, if an inverter receives 100 watts of DC power and delivers 90 watts of AC power, its efficiency is 90%.

Currently, solar inverters in Europe and the United States are known for their high efficiency, often reaching up to 97.2%, although they tend to be more expensive. In contrast, many inverters in China have an efficiency below 90% but are significantly more affordable. Efficiency is not just about power conversion—it also plays a crucial role in energy savings, especially in low-power systems where even small improvements in efficiency can make a big difference in overall performance.

According to the source nature:

Active inverter: An inverter that feeds power back into the grid without directly connecting to the load on the AC side.

Passive inverter: An inverter that directly supplies power to the load, converting DC to AC at a fixed or variable frequency without connecting to the grid.