Inverters are commonly used to supply AC power from DC sources such as solar panels or batteries.
The inverter performs the opposite function of a rectifier.
There are three major types of inverters and they include Pure sine wave, modified sine wave and Square Wave.
Pure Sine Wave Inverters
The best power source for most applications is a pure 60Hz sine wave, identical to the 120Vrms source available from any US power company. All low power household plug-in devices are designed to work with this source (high power devices such as cooking ovens use a 240V source) and, as such, will be most likely to work properly and most efficiently on such a source. A true sine wave source is produced most easily for high power applications through rotating electrical machinery such as naval gas-turbine generators, house-hold diesel or gasoline backup generators, or the various generators employed by power companies that employ a shaft torque to create an AC current. These sources provide a relatively clean, pure sine wave (lacking significant harmonics and high frequency noise) thanks to their analog rotational make-up. Such rotating machinery can be inappropriate for low-power backup supply usage due to their high cost, large size and required maintenance. As such, a smaller, digital pure sine wave inverter can be extremely useful.
Square Wave Inverters. DC to AC conversion is most commonly done through use of MOSFET inverter circuits, which can switch the voltage across the load, providing a digital approximation of the desired AC signal. The simplest variant of this inversion is the production of a square wave approximation of a sine wave. For a square wave, the load voltage must be switched merely from high to low, without the need for an intermediate step (i.e. 0V). In order to deliver the same power as the sine wave to be approximated, the amplitude of the square wave must be the sine wave's RMS value. This way, the average voltages, and therefore the power delivered, will be the same for the two waveforms. Square wave inverters are very rarely used in practice, as many devices which utilize timing circuits that rely on something close to the sine wave from the power company cannot operate with such a rough approximation. In addition, a square wave has relatively large 3rd and 5th harmonic components, which burn power and severely cut down on the efficiency of devices using such inverters as a power source.
Modified Sine Wave Inverters
A very common upgrade to the square wave inverter is the modified sine wave inverter. In the modified sine wave inverter, there are three voltage levels in the output waveform, high, low, and zero, with a dead zone between the high and low pulses. The modified sine wave is a closer approximation of a true sine wave than is a square wave, and can be used by most household electrical devices. As such, it is extremely common to see this type of inversion in commercial quality inverters. Despite being much more viable than a simple square wave, the modified sine wave has some serious drawbacks. Like the square wave, modified sine waves have a large amount of power efficiency loss due to significant harmonic frequencies, and devices that rely on the input power waveform for a clock timer will often not work properly. Despite the inherent drawbacks, many devices can work while powered by a modified sine source. This makes it an affordable design option for such implementations as household uninterrupted power supplies.
More info on the way.....
