Inverter – Definition and Classification of Inverters:

A device that converts dc power into ac power at desired output voltage and frequency is known as an inverter. Some industrial applications of inverters are for adjustable-speed ac drives, induction heating, standby aircraft power supplies.

The dc power input to the inverter may be battery, fuel cells, solar cells or other dc source. But in most industrial applications, it is supplied by a rectifier. The configuration of ac to dc converter and dc to ac inverter is called a dc link converter because it is a two-stage static frequency converter in which ac power at network frequency is rectified and then filtered in the dc link before being inverted to ac at an adjustable frequency.

Inverters can be classified in a number of ways. An inverter may be a single-phase inverter or 3-phase inverter depending on whether the output is single-phase or 3-phase ac.

Another Classification of Inverters is as per the method of commutation, i.e., line commutated inverter and forced commutated inverter. A line commutated inverter feeds an ac system. The ac line voltage is used for commutation. As the ac voltage goes to zero and reverses the thyristor is turned off. The force commutated inverters use one of the methods of forced commutation.

Another Classification of Inverters is as per the connections of thyristors and commutating elements. In this category are series inverter, parallel inverter and bridge inverter.

Another Classification of Inverters is voltage source and current source inverters. A voltage source inverter is fed by a constant voltage source system while a current source inverter is fed by a constant current source.