Inverter Quasi-sine Wave

These inverter produce a waveform that has an intermediate voltage level which brings it closer to a sine wave. Sine wave inverters produce an actual sine wave. Sine wave inverters are more expensive than the square wave and the modified sine wave inverters.

The square wave, modified sine wave, and quasi-sine wave all have a number of harmonics, which, as you know, are sine waves with frequencies that are odd multiples of the fundamental frequency and different amplitudes. Harmonics are especially troublesome in some applications, so high-quality sine wave inverters are the most widely used type.

Sine wave inverters are more expensive than the square wave and the modified sine wave inverters. However, they are ideal as electric devices such as motors, Television sets, chargers are designed to use a natural sine waveform. Using square wave inverters on these devices can produce harmonic distortion, humming.

In fact, the output of a modified sine wave inverter is a combination of two square waves having a phase difference of 90 degrees superimposed over each other. As a result, contrary to a square wave which has only two voltage levels (peak to peak voltages), the resultant wave has three voltage levels – positive peak, zero level and negative peak.

The result is a reduced harmonic content that has less distortion than the modified sine wave. This waveform is sometimes referred to as a quasi-sine wave, although this term is also sometimes used to describe the two-level modified sine wave. Figure 6 Three-Level Modified Sine Wave Creating a Quasi–Sine Wave

A pure sine wave inverter has several advantages over its previous two forms: More efficiency, hence consumes less power. They can be adjusted according to your personal power requirements, since several types are available with different power outputs.