Usefulness of frequency change feature by inverter can be seen in AC (Air Conditioner). AC uses compressor to cool the room. In AC without an inverter, this compressor can only run at full speed, or not run at all. If the room temperature is too high than the set temperature, the compressor is run, if too low, the compressor is turned off.
The rotational speed of the compressor is regulated by the frequency of alternating current fed so that the electric current from the mesh can only rotate the compressor in one speed. By setting the frequency by the inverter, the compressor speed can be adjusted so that it does not need to be switched on, but runs at a certain speed (Not necessarily full speed).
A constantly running compressor consumes less energy than a compressor that is turned on and off repeatedly. This is because when it starts up, the compressor needs a large instantaneous power (it can be shown with a flashing home light when you turn on the AC). Then, AC that uses inverter can be more efficient than AC without inverter. In addition to air conditioning, inverters are also used for other applications.
Generally used to run tools made of electric motors AC (alternating current), eg water pump. In the industrial world, the term inverter commonly refers to the AC motor controller. Actually this tool consists of a rectifier (converting AC current to DC) and an inverter (DC to AC), but a common one is called an inverter.