What's the difference between modified sine wave and pure sine wave?

Waveform Comparison

The primary difference between modified sine wave and pure sine wave inverters lies in their output waveform. A modified sine wave inverter produces a waveform with a frequency of 50 or 60 Hz, but with a distorted wave shape, typically with 10-20% total harmonic distortion (THD). This means that the output voltage and current do not follow the ideal sine wave pattern, which can cause issues with sensitive equipment. In contrast, a pure sine wave inverter produces a waveform with a frequency of 50 or 60 Hz and a THD of less than 5%, ensuring that the output voltage and current follow the ideal sine wave pattern.

Load Sensitivity

When choosing between a modified sine wave and a pure sine wave inverter, it is essential to consider the type of loads you will be powering. Non-sensitive loads, such as incandescent lighting and refrigeration units, can operate on a modified sine wave. However, sensitive loads, such as computers, medical equipment, and variable speed drives, require a pure sine wave to function correctly. If you plan to power sensitive equipment, it is essential to choose a pure sine wave inverter to ensure reliable operation.

Solar Inverter Sizing

When sizing a solar inverter, it is crucial to consider the load requirements and the type of inverter you choose. A pure sine wave inverter will typically require a larger capacity to meet the same load requirements as a modified sine wave inverter, due to the increased efficiency and reduced harmonics. As a general rule of thumb, a pure sine wave inverter will require 10-20% more capacity than a modified sine wave inverter to meet the same load requirements.