The inverter is a basic component on medium to large systems which converts low voltage DC power from the batteries into high voltage (usually 120 or 240) AC power as needed.
Inverters of the past were inefficient and unreliable. Today's generation of inverters are very efficient (85 to 94%) and very reliable.
Today, the majority, if not all of the loads in a typical remote home operate at 120 VAC from the inverter. The only reason to operate select loads at low voltage DC is to maximize efficiency.
Most inverters we sell produce only 120 VAC, not 120/240 VAC as in the typical utility connected home. The reason being, once electrical heating appliances are replaced with gas appliances, there is little need for 240 VAC power. Exceptions include good-sized submersible pumps and shop tools which can either be powered by the generator, step-up transformer, or possibly justify the cost of a larger or second inverter.
Two types of inverters predominate the market modified sine and sine wave inverters.
Modified sine wave units are less expensive per watt of power and do a good job of operating all but the most delicate appliances. Sine wave units produce power which is almost identical to the utility grid, will operate any appliance within their power range, and cost more per watt of output.
Inverter to battery cabling. Because of the high current required on low voltage circuits, this cable is large, commonly #2 to 4/0 in size. Smaller conductors than required are unsafe and will not allow the inverter to perform to its full rating.
DC input disconnect and overcurrent protection. It is important to have a safe installation with a properly sized DC rated, UL listed disconnect. Typically the disconnect works in conjunction with a overcurrent protection device such as a fuse or breaker. These components are installed in an enclosure which can also house shunts.
Shunts - Used to read the amperage flowing between the battery and inverter, this device is installed in the negative conductor. It can easily be housed in the disconnect or its own enclosure.
AC output disconnect and overcurrent protection. If the breaker panel, which is fed from the inverter, is adjacent to the inverter, then the main breaker will serve as the inverter output disconnect and overcurrent protection. If, however, this panel is not grouped with the inverter, then a separate unit should be installed. This also holds true with AC circuits coming to the inverter from a generator or utility source. A second breaker may be needed if these breakers are not grouped.
Inverters with Built-In Battery Chargers
Many of today's inverters incorporate battery charging circuitry. This is easily and economically accomplished because of the design of most inverters. Inverters step up low voltage and change DC power to AC power. Battery chargers do the reverse of this. Additional circuitry is all that is required to add a whole second function and economically create an Inverter/Charger.
Transfer switches are also incorporated into these Inverter/Chargers so that the AC loads can be powered directly from the generator when the battery charger is operating.
From a reliability, performance, and economical standpoint, built-in battery chargers are the way to go.
Inverters are compared by three factors:
- Continuous wattage rating. Hour after hour, what amount of power in watts can the inverter deliver.
- Surge Power. How much power and for how long can an inverter deliver the power needed to start motors and other loads.
- Efficiency. How efficient is the inverter at low, medium and high power draws. How much power is used at idle.
Inverter Over current Protection, Cable and Power center Sizing Chart
|Over current||Minimum||Power center|
|Name||Model||Wattage||Voltage||Input Amperage||In Amps||Size'"
|Stat Power Prosine||1.2-12||1200||12||128||175||2/0||3-202|
|Stat Powe Prosine||2.5-12||2500||12||267||400||4/0'||3-404|
|Stat Power Prosine||2.5-24||2500||24||134||175||2/0||3-202|
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