What is an Inverter?

An inverter is an electrical or electro-mechanical device that converts direct current (DC) to alternating current (AC). Inverters are used in a wide range of applications, from small switching power supplies in computers, to large electric utility applications that transport bulk power. The inverter is so named because early mechanical AC to DC converters were made to work in reverse, and thus were “inverted”, to convert DC to AC. The inverter performs the opposite function of a rectifier.

Modified Sinewave Inverters

Pure Sinewave Inverters

UPS Inverters

180px-inverter_ckt_01cjcBasic Inverter designs

In one simple inverter circuit, DC power is connected to a transformer through the centre tap of the primary winding. A switch is rapidly switched back and forth to allow current to flow back to the DC source following two alternate paths through one end of the primary winding and then the other. The alternation of the direction of current in the primary winding of the transformer produces alternating current (AC) in the secondary circuit.

The electromechanical version of the switching device includes two stationary contacts and a spring supported moving contact. The spring holds the movable contact against one of the stationary contacts and an electromagnet pulls the movable contact to the opposite stationary contact. The current in the electromagnet is interrupted by the action of the switch so that the switch continually switches rapidly back and forth. This type of electromechanical inverter switch, called a vibrator or buzzer, was once used in vacuum tube automobile radios. A similar mechanism has been used in door bells, buzzers and tattoo guns.

As they have become available, transistors and various other types of semiconductor switches have been incorporated into inverter circuit designs.

 Examples of Inverter Applications

180px-inverter_cjc01DC power source utilization
Inverter designed to provide 115 VAC from the 12 VDC source provided in an automobileAn inverter converts the DC electricity from sources such as batteries, solar panels, or fuel cells to AC electricity. The electricity can then be used to operate AC equipment such as those that are plugged in to most house hold electrical outlets.

Uninterruptible Power Supplies (UPS)
An uninterruptible power supply is a device which supplies the stored electrical power to the load in case of raw power cut-off or blackout. One type of UPS uses batteries to store power and an inverter to supply AC power from the batteries when main power is not available. When main power is restored, a rectifier is used to supply DC power to recharge the batteries.