A basic inverter is around the size of an average VCR. It contains an AC to DC convertor on the input stage, a charger circuit, which utilizes this DC to charge the connected batteries, a relay circuit for switching and a final DC to AC converter stage. An inverter is calculated in KVA, similar to a UPS. These range from 500 VA to around 10,000 VA and above, with the most popular 600 VA used in homes and small offices.
The batteries used for inverters are usually lead-acid (like those used in automobiles). It supplies a voltage of 12 V DC with a specific power rating ranging from 40 AH to 200 AH and above. The most popular ones used are 100 AH and 150 AH.
Multiple batteries are connected together to get a higher rating according
to the necessary power needs. Batteries can cost around Rs 5,000 and above (it also depends upon the price of lead in the market). Inverters and batteries are sold separately.
Types of inverters
Inverters are available in two forms or types - pure sine wave inverters and modified sine wave (also known as quasi sine wave) inverters. These two types are differentiated from each other by the properties of the waveform generated when they convert DC voltage into AC.
Also known as true sine wave inverters, they are very expensive. These inverters can provide clean power output and can be used in certain types of electrical and electronic equipment such as timers, certain medical equipment, chargers, printers, etc. The power output is clean and contains none or negligible electrical noise (spikes). These inverters similar to a UPS, are made of high frequency circuits, and cannot afford to be overloaded.
Hence, these inverters need to be configured to match the exact or higher load power rating. Overloading would result in a damaged inverter.
Modified sine wave inverters
Also known as Quasi sine wave inverters, these are usually cost effective as compared to pure sine wave inverters. The output wave form is around 60 to 80 percent similar to that of the input waveform. This means that the voltage output would be the same, but the quality would not be 100 percent. These types of inverters are rugged and can be used where power conditions are erra;tic. such as rural India and industrial areas. where the lines fluctuate, are leaky, and have almost no earthing connections.
These inverters are usually transformer-based and are heavier and comparatively cheaper to manufacture. Also this type of inverter can handle an overload. When one is detected, the inverter switches off. When the load is reduced, it comes on again. Finally, you don't need to have separate wiring if you wish to employ these inverters.