Everything you need to know
What is an Inverter?
An inverter converts the DC voltage to an AC voltage.
In most cases, the input DC voltage is
usually lower while the output AC is equal to the grid supply voltage of either 120 volts, or
240 Volts depending on the country.
The inverter may be built as standalone equipment for applications such as solar power, or to work as a backup power supply from batteries which are charged separately.
The other configuration is when it is a part of a bigger circuit such as a power supply unit, or a UPS.
In this case, the inverter input DC is from the rectified mains AC in the PSU, while from either the rectified AC in the in the UPS when there is power, and from the batteries whenever there is a power failure.
Basic inverter operation
The basic circuits include an oscillator, control circuit, drive circuit for the
power devices, switching devices, and a transformer.
The conversion of dc to alternating voltage is achieved by converting energy stored in the dc source such as the battery, or from a rectifier output, into an alternating voltage.
This is done using switching devices which are continuously turned on and off, and then stepping up using the transformer. Although there are some configurations which do not use a transformer, these are not widely used.
Inverters are used for a variety of applications that range from small car adapters to household or
office applications, and large grid systems.
Uninterruptible power supplies
As standalone inverters
In solar power systems
Inverter output waveforms
The inverters are classified according
to their output waveforms with the three common types being the square wave, the pure sine wave
and the modified sine wave.
The square wave is simple and cheaper, however, it has a low power quality compared to the other two. The modified square wave provides a better power quality (THD~ 45%) and is suitable for most electronic equipment.
These have rectangular pulses that have dead spots between the positive half cycle and the negative half cycle (THD about 24%).