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Inverters change Direct Current (DC) to Alternating Current
(AC). Stand-Alone inverters can be used to convert DC from a
battery to AC to run electronic equipment, motors, appliances,
etc. Synchronous Inverters can be used to convert the DC output
of a photovoltaic module, a wind generator or a fuel cell to
AC power to be connected to the utility grid. Multifunction inverters
perform both functions.
 Synchronous
Inverters
Synchronous inverters change DC power into AC power to be
fed into the utility grid. A power system with this type of inverter
uses the utility company as a storage battery. When the sun is
shining, your electricity comes from the PV array, via the inverter.
If the PV array is making more power than you are using, the
excess is sold to the utility power company through a second
electric meter. If you use more power than the PV array can supply,
the utility makes up the difference. This type of system makes
the most sense if you have utility power, because there are no
batteries to maintain or replace, but it has a very long payback
period and may not be cost-effective at today's electric rates.
Using a multifunction inverter allows you to sell excess power
to the utility, and also maintain a battery bank for stand-by
power in the event of a utility power failure.
Multi-function
Inverters
Trace Engineering Company produces a line of true sine wave
inverters called the SW line, that can operate as Stand-Alone
inverters and as Synchronous inverters at the same time! In a
typical installation, the Trace SW inverter is connected to a
battery bank, the utility power lines, a standby generator and
the house load center. When batteries are in a charged condition,
the SW inverter supplies AC power to the house from the batteries.
If the batteries become discharged, the inverter supplies the
house loads from the utility lines, while charging the batteries.
If the batteries become fully charged by another power source,
such as photovoltaic modules or a wind or hydroelectric generator,
excess power may be sold back to the utility. If utility power
fails, the inverter can still operate, supplying critical loads.
If a standby generator is started, it can also supply power to
loads. The inverter will synchronize to the generator and allow
loads to be powered that are too large for either the generator
or inverter to supply alone.
Stand-Alone
Inverters
Stand-Alone inverters convert DC power stored in batteries
to AC power that can be used as needed. Selecting an inverter
for your power system based on the maximum load you will be powering,
the maximum surge required, output voltage required, input battery
voltage and optional features needed. High quality stand-alone
inverters are available in sizes from 100 watts, for powering
notebook computers and fax machines from your car, to 8000 watts,
for powering an entire house or small commercial operation. The
size of an inverter is measured by its maximum continuous output
in watts. This rating must be larger than the total wattage of
all of the AC loads you plan to run at one time. The size of
the inverter can be minimized if the number and size of the AC
loads is kept under control. Wattage of most AC loads can be
determined from a tag or label on the appliance, usually located
near where the power cord enters, or from the owner's manual.
If the inverter is expected to run induction motors, like the
ones found in automatic washers, dryers, dishwashers and large
power tools, it must be designed to surge, or deliver power many
times its rating for short periods of time while these motors
start.
Stand-alone inverters are available with three basic power
output waveforms: square wave, modified square wave (sometimes
called modified sine wave) and pure sine wave. Synchronous Inverters
and Utility companies deliver a pure sine wave.
Square wave inverters have the lowest cost and efficiency
and are not sold in this catalog. The price of the better quality
inverters is low enough to make square wave inverters an unattractive
choice.
Trace 700/800series, DR series, U series inverters and Genius
inverters have modified square wave output with harmonic distortion
of around 40%. They are an economical choice in power systems
where waveform is not critical. Their high surge capacity allows
them to start large motors while their high efficiency makes
them economical with power when running small loads like a stereo
or a small light. They can power most lighting, televisions,
appliances and computers very well. We do not recommend them
for computer systems with laser printers. Unfortunately, this
type of inverter may destroy some low cost rechargeable tools
and flashlights, and their waveform will not allow many laser
printers, copiers, light dimmers and some variable speed tools
to operate. Some audio equipment will have a background buzz
that may be annoying to music connoisseurs.
Sine wave inverters have a slightly higher cost, but they
can operate almost anything that can be operated on utility power.
Trace Sinewave inverters are available in sizes from 2500 watts
to 5500 watts, and a pair of them can be synchronized to deliver
up to 11,000 watts. They are an excellent choice for a 'whole
house" inverter. Exeltech sinewave inverters, available
in sizes from 150 watts to 2000 watts, are an excellent choice
for power systems running audio equipment and other electronics
that are waveform-sensitive. Larger Sinewave inverters are available
in sizes up to 200,000 watts, that can run a small village.
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