• inverter basics

    Using an Inverter in a solar power system
    An inverter changes DC power stored in a battery to standard 120/240 VAC electricity (also referred to as 110/220). Most solar power systems generate DC current which is stored in batteries or fed directly into the grid with a grid tie inverter. Nearly all lighting, appliances, motors, etc., are designed to use ac power, so it takes an inverter to make the switch from battery-stored DC to standard power (120 VAC, 60 Hz).

    The inverter switches direct current (DC) back and forth to produce alternating current (AC). The resulting AC current is transformed, filtered etc. to produce an acceptable output waveform. The more processing, the cleaner and quieter the output, but the lower the efficiency of the conversion. The goal becomes to produce a waveform that is acceptable to all loads without sacrificing too much power into the conversion process.

    Two basic inverter outputs designs are available – sine wave and modified sine wave. Most ac devices can use the modified sine wave, but there are some notable exceptions. Laser printers which use triacs and/or silicon controlled rectifiers are damaged when provided mod-sine wave power. Motors and power supplies usually run warmer and less efficiently on mod-sine wave power. Items such as fans, amplifiers, and cheap fluorescent lights, give off an audible buzz on modified sine wave power. However, modified sine wave inverters make the conversion from DC to AC very efficiently, they are relatively inexpensive and can power many common electrical devices very effectively.

    Sine wave inverters can virtually operate anything. Your utility company provides sine wave power, so a sine wave inverter is equal to or even better than utility supplied power. A sine wave inverter can “clean up” utility or generator supplied power because of its internal processing. All grid tie inverters are true sine wave inverters

    Inverters are made with various internal features and many permit external equipment interface. Common internal features are internal battery chargers which can rapidly charge batteries when an AC source such as a generator or utility power is connected to the inverter’s INPUT terminals. Auto-transfer switching is also a common internal feature which enables switching between different AC sources, or from utility power to inverter power for designated loads. Battery temperature compensation, internal relays to control loads, automatic remote generator starting/stopping and many other programmable features are available.

    Most inverters produce 120VAC, but can be equipped with a step-up transformer to produce 120/240VAC. Some inverters can be series or parallel “stacked-interfaced” to produce 120/240VAC or to increase the available amperage. There are new inverters on the market today that are capable of producing both 120/240 VAC and most grid tie inverters produce 240 VAC because it is more efficient.