An inverter is a device that changes or transforms a direct current input voltage to a symmetrical output voltage (sinusoidal, square or triangular) of alternating current, with the magnitude and frequency desired by the user or designer.

Inverters are used in a wide variety of applications, from small power supplies for computers, to industrial applications to control high power. Inverters are also used to convert the direct current generated by photovoltaic solar panels,[1]​ accumulators or batteries, etc., into alternating current and in this way can be injected into the electrical grid or used in isolated electrical installations.

Inverter air conditioning or inverter is a type of air conditioner that uses a power inverter to set the speed of the compressor motor and thus leave the temperature constant, thereby saving a minimum of 40% of electricity.

A simple analog inverter consists of a coil (inductor) and a switch, which is used to interrupt the current and collapse the magnetic field of the coil generating a reverse pulsating wave.

This reverse pulse wave is time-varying and can induce current.

A simple digital inverter consists of an oscillator that controls a transistor, which is used to interrupt the incoming current and generate a rectangular wave.

This rectangular wave feeds into a transformer which smoothes its shape, making it look a little more like a sine wave and producing the necessary output voltage.

The voltage output waveform of an ideal inverter should be sinusoidal. A good technique to achieve this is to use the PWM technique making the principal sinusoidal component much larger than the higher harmonics.

More modern inverters have begun to use more advanced forms of transistors or similar devices, such as thyristors, triacs, IGBTs and MOSFETs.

The most efficient inverters use various electronic filters to try to arrive at a waveform that reasonably simulates a sine wave at the input of the transformer, rather than relying on the transformer to smooth the waveform.

They can be generally classified into two types: 1) single-phase inverters and 2) three-phase inverters.