INVERTERS - GENERAL INFORMATION
Why an inverter is needed
The utility grid supplies you with alternating current (AC) electricity. AC is the standard
form of electricity for anything that “plugs in” to the utility power. Direct current (DC)
electricity flows in a single direction. Batteries provide DC electricity. AC alternates its
direction many times per second. AC is used for grid service because it is more practical
for long distance transmission. For more details read
“Characteristics of Sinusoidal AC
Power” on page 7
An inverter converts DC to AC, and also changes the voltage. In other words, it is a
power adapter. It allows a battery-based system to run conventional AC appliances
directly or through conventional home wiring. There are ways to use DC directly, but for
a modern lifestyle, you will need an inverter for the vast majority, if not all of your loads
(
in electrical terms, “loads” are devices that use electrical energy
).
Incidentally, there is another type of inverter called grid-interactive. It is used to feed
solar (or other renewable) energy into a grid-connected home and to feed excess energy
back into the utility grid. This inverter is
NOT grid interactive
Inverter should meet the application
To choose an inverter; you should first define your needs. Where is the inverter to be
used? Inverters are available for use in buildings (including homes), for recreational
vehicles, boats, and portable applications. Will it be connected to the utility grid in some
way? Electrical conventions and safety standards differ for various applications, so don’t
improvise.
Electrical Standards
The DC input voltage must conform to that of the electrical system and battery bank. 12
volts is recommended for small, simple systems. 24 and 48 volts are the common
standards for higher capacities. A higher voltage system carries less current, which makes
the system wiring cheaper and easier.
The inverter’s AC output must conform to the conventional power in the region in order
to run locally available appliances. The standard for AC utility service in North America
is 120 and 240 Volts at a frequency of 60 Hertz (cycles per second). In Europe, South
America, and most other places, it is 230 volts at 50 Hertz.
Power capacity
– “Continuous” and “Surge”
How much load can an inverter handle? Its power output is rated in Watts. Read details
under
“Characteristics of Sinusoidal AC Power” on page 7.
There are two levels of
power rating -a
continuous rating
and a
surge rating
. Continuous means the amount of
power the inverter can handle for an indefinite period of hours. When an inverter is rated
at a certain number of Watts, that number generally refers to its continuous rating. The
“surge power”
indicates the power to handle instantaneous overload of a few seconds to
provide the higher power required to start certain type of devices and appliances.
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