POWER INVERTERS 12V TO 230V
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Joined: Sep 2010
15-10-2010, 11:00 AM
POWER INVERTER DOC..docx (Size: 64.24 KB / Downloads: 151)
An inverter is an electrical device that converts direct current (DC) to alternating current (AC); the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits.
Static inverters have no moving parts and are used in a wide range of applications, from small switching power supplies in computers, to large electric utility high-voltage direct current applications that transport bulk power. Inverters are commonly used to supply AC power from DC sources such as solar panels or batteries.
The electrical inverter is a high-power electronic oscillator. It is so named because early mechanical AC to DC converters were made to work in reverse, and thus were "inverted", to convert DC to AC.
The inverter performs the opposite function of a rectifier.
Power Inverters or DC to AC Power Inverters is a group of devices that simply convert DC electricity to AC Electricity. DC electricity is the type of power most often associated with battery power. AC power is most often associated with your household power or grid power. A power inverter comes in handy when you have DC power available and would like AC power. Simply hook the power inverter to the battery source and turn it on to get the power you need. Although this is a simplified use of an inverter, they aren't terribly more complicated. There are a couple items you need to consider when purchasing a power inverter.
Firstly, one will need to address the power output of the power inverter desired. This is often measured in watts and will directly correlate to its capacity for delivering power. Most power inverters will have a continuous rating and a surge rating, some will even have a five minute rating. This rating will advise on how much power the unit can produce for a certain time period. The most important rating will always be it continuous rating because if your device falls within the power inverter continuous output, it will run without issue. The five minute rating is as stated but the surge rating is usually for only a few seconds at most. I always suggest that my customers buy an inverter that is one size larger than they need and try to avoid inverters over 3000 watts of power unless they have an unlimited source of DC power. The reason for over sizing is that when you need a little more power you will have to buy another power inverter and don't buy over 3000 watts because it isn't practical for most applications. Don't fall prey to the "I need the largest inverter available" logic because you will also need the heaviest battery bank available as well.
Secondly, one will need to determine the best waveform for your power inverter. There are two basic types modified sine power inverters and true or pure sine wave power inverters. Modified sine wave inverters are the older and usually less expensive technology for replicating AC power. They can produce power that can fool many devices, but is not the best. A true sine wave inverter on the other hand is the best technology that will produce power that is equivalent to grid power or better. So all your devices will run on these inverters. This includes items that will not run on modified sine inverters like oxygen concentrators, laser printers, some variable speed motors, certain fax machines, laptops and other more sensitive pieces of equipment. The standard for purchasing power inverters today has been set at true sine wave.
A few pointers for purchasing power inverters is to look for UL listed inverters, GFCI outlets, and installation accessories designed for use with a particular power inverter are available from the same manufacturer. Also try to purchase your inverter from a retailer that will offer great technical support before and after the sale, avoid sales people and stores that will sell you any inverter without many questions. Also remember you are dealing with electricity and if you aren't familiar with safe operation and installation, hire a professional.
Joined: Apr 2012
27-06-2012, 05:37 PM
Power Inverters 12V to 230V
Power Inverters.pdf (Size: 934.67 KB / Downloads: 51)
An inverter allowes the use of 230V electrical appliances from a car battery or a solar battery. It must therefor supply
a voltage that corresponds to an rms of 230 Volts sine-wave like household main supply or similar. Sine-wave
voltages are not easy to generate. The advantage of sine-wave voltages ist the soft temporal rise of voltage and the
absence of harmonic oscillations, which cause unwanted counter forces on engines, interferences on radio
equipment and surge currents on condensers. On the other hand, square wave voltages can be generated very
simply by switches, e.g. electronic valves like mosfet transistors. In former times electromagnetical switches, that
operated like a door bell were used for this task. They were called "chopper cartridge" and mastered frequencies up
to 200 cycles per second. The efficiency of a square wave inverter is higher than the appropriate sine wave inverter,
due to its simplicity. With the help of a transformer the generated square wave voltage can be transformed to a value
of 230 Volts (110 Volts) or even higher (radio transmitters e.g.).
A transformer will provide best characteristics when the primary coil, that takes over magnetization of the iron core,
fits closely around the core. For industrial transformers this would be the 230 Volts coil, on our inverters however it
will be the 12 volt coil.
Current densities from 3.5 A/mm2 to 4 A/mm2 are used on industrial transformers. If our inverter is not beeing used
excessivly, current densities may even be higher. A transformer with 1000 VA needs approx. 84 ampere from the 12
Volt battery on nominal load. Since the two primary coils alternate mutually, we may count from 42 amperes. (This is
strictly not correct, since the acceptance applies only if both windings would exhibit double surface for heat
emission). For a round wire this would mean a diameter of 4 mm. Such wire is hardly to wind, also automats can't do
it perfectly. A solution may be wires with rectangular cross section or several smaller wires in parallel.
After winding the transformer, the sheet metals must be inserted again. With each layer we change the direction of
the sheet metals, while in the original condition several sheet metals were probably summarized into packages, in
order to increase the air gap and linearize magnetizing currents. This effect isn't needed for our inverter. Magnetizing
currents are always extremely nonlinear in square wave transformers, and they are asymmetrical also. This has no
effect on the performance of the inverter and the output voltage.