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The inverter is the heart of all AC solar energy systems. It is an electronic device that converts direct current (DC) power from batteries or solar panels into alternating current (AC) power the same as supplied by a utility company. This power is used to operate lights, appliances or anything that normally operates on power supplied by the utility company. Inverters come in many varieties, sizes and qualities and offer various features that specialize them for particular applications. Common inverter types include Grid-Tie, Grid-Interactive, Stand-Alone Sinewave, Stand-Alone Modified Sinewave, & Portable Inverters. Grid-Interactive and some Stand-Alone or Off-Grid inverters have built-in battery chargers. These are the brands which we represent...
APOLLO SOLAR
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· EXELTECH
· FRONIUS
· KACO
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Stand-Alone Inverters convert DC power stored in batteries to AC
power that can be used as needed. Select an inverter for your power system
based on the maximum load you will be powering, the maximum surge required,
AC 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 60
kilowatts, for powering a 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. 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 top loading 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 two basic power output waveforms: modified square wave (often called modified sine wave) and sine wave. Intertie, multifunction inverters and utility companies deliver a sine wave.
Xantrex DR series and Samlex PSE inverters have modified sine 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. Unfortunately, this type of inverter may destroy some rechargeable tools and flashlights, and laser printers and copiers. They may not allow many laser printers, copiers, light dimmers and some variable speed tools to operate. Equipment with silicon controlled rectifiers (or SCRs) will not operate. Some audio equipment will have a background buzz that may be annoying to music connoisseurs.
Exeltech, Xantrex SW Series, SMA Sunny Island and Outback FX inverters are sine wave inverters. Sine wave inverters have a higher cost, but they can operate almost anything that can be operated on utility power. Exeltech sinewave inverters are an excellent choice for power systems running audio or telecommunications equipment and other electronics that are waveform-sensitive. The Outback and Xantrex SW series inverters can be ganged together for up to 36 kW of output and can operate off-grid or intertied. We now carry Samlex Sine Wave PST inverters for a lower cost, small system Sine Wave alternative.
Stand-Alone Inverters come in several configurations....
Intertie inverters convert DC power from PV modules into AC power to be fed into the utility grid. There are two major types of utility inverters; string inverters and low voltage input inverters.
The SMA Sunny Boy, Fronius and Xantrex GT-3 inverters are referred to as string inverters. The name "string" comes from the way the PV modules are wired together, in series to achieve a higher voltage. These inverters are designed to run at voltages up to 600 VDC. String wiring is faster to install, more efficient and allows the use of smaller guage wire. DC voltage this high can be deadly, so string inverters should be installed and serviced by qualified electricians.
A utility-tie PV system 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 generating more power than you are using, the excess can be sold to the utility (power company) through yor 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. Unfortunately, if the utility power goes down, this type of inverter will go off, too.
Using a multi-function inverter allows
you to sell excess power to the utility, and also maintain a battery bank
for standby power in the event of a utility power failure.
The Outback GFX and Xantrex SW series are primarily stand-alone inverters that can function as an intertie inverter at the same time, but with a slightly lower efficiency than an inverter designed for intertie only.
The Outback PS1 and Beacon Power M5 are intertie inverters that are designed to provide battery backup when the utility fails.
The SMA Sunny Island inverter is designed to work with a Sunny Boy inverter to provide utility intertie with battery backup. In a typical installation, the inverter is connected to a battery bank, the utility power lines, a standby generator and the house load center.
If the utility is available, the inverter will supply the house loads from the utility. If the utility fails, the inverter will supply power to the loads from the battery. When the utility is available again, the inverter will switch the loads back to the utility, and recharge 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.
Output Voltage
We sell inverters that supply standard 120VAC 60 HZ (and stacked inverters for 240VAC), such as one gets from utility companies and fuel-powered generators. Most of them can be special ordered with other output voltages and frequencies for use anywhere in the world. See our export models and contact us with any special requirements that you have.
Interference
The electronic circuitry in inverters may cause problems with radio and television reception, noise on telephones and buzz in audio equipment. Sine wave inverters cause the least amount of interference. Interference can be minimized by locating the inverter very close to the batteries, twisting together the cables that connect the inverter to the battery, running AC lines separate from other wiring (such as telephone wires) and locating the inverter away from appliances that are susceptible to interference. All inverters cause interference on AM radio!
Wiring Considerations
Stand-alone inverters require very high current from a battery to operate large loads. A 2000 watt inverter running at full power in a 12 volt system will be drawing nearly 200 amps from the battery. Large cables and good connections are required for proper operation. Use caution when plugging a small inverter into a lighter outlet located far from a battery. Typical DC house wiring may have insufficient wire sizes and too much voltage drop to supply the current required by these inverters. All battery-based inverters require proper fusing between the battery and the inverter.
Grid Priority Inverters can be used in both solar and in applications where your utility electric is extremely unreliable. When utility electric is available these inverters will choose the utility electric first. They make for a good and reliable off-grid inverter as well, and they are relatively inexpensive way to go.
For solar users who may have access to utility electric for back up these types of inverters may present a problem as they will only use the solar as a back up. You can get around this by using our Samlex Battery Guard and a relay. This will keep the utility electric isolated from the inverter until the batteries are drained to a low level. The Battery Guard then activates the relay which connects the inverter to the grid.
Lets say your main source of electric may come from your utility which may be reliable about four hours a day (I have seen this in Mexico and on some Caribbean Islands). While there is electric your energy is supplied by the utility or in some cases by a community generator which also charges your battery bank so that you have electric during the period of time when there is no utility or generator.
Since it is costly to purchase electric in these areas it is recommended that you supplement your power system with solar.
These inverters come in both Sinewave and Modified Sinewave versions and include built in battery chargers.
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