Inverters

Wednesday, April 23, 2008

I need an inverter

If you need an inverter design of any capacity that can meet your load demand,please send all correspondence to taiyedipo@gmail.com or call mobile numbers: 08055081359,08064272866. You may contact this email:olamicspirit2003_ng@yahoo.com also.

Thank you

What can an inverter do for you

Inverter
Inverter power is a great way to provide reliable electricity to many applications. We have an inverter in our Garage, our car, our boat, and our RV. We have even used an Inverter to run a pinic in the middle of a baseball diamond. Inverters are so versatile because they allow you to turn readily available DC power into the more desired AC power. So whenever you need remote power, what can an Inverter Do For You?

Inverter Power Can Really Handle Emergency Outages
Many times we have power outages, we want to run a TV or radio to find out what is happening in the world around us. This is hard to do if you do not have a battery powered product. With an Inverter you can run most small low load AC devices using your car battery in an emergency. A power inverter will convert your cars battery power to 120 Volts AC power. This will allow you to plug in your TV and see whats going on.

Camera Charged By Inverter on Turtle Hospital Visit
We went to the Florida Keys in late January and Early February 2008. We stopped at the Turtle hospital in Marathon. This place rocks!!!! Read more on how an inverter helped us capture some great pictures!

DC to DC converters

Variable 3 - 24 Volt / 3 Amp Power Supply
This regulated power supply can be adjusted from 3 to 25 volts and is current limited to 2 amps as shown, but may be increased to 3 amps or more by selecting a smaller current sense resistor (0.3 ohm). The 2N3055 and 2N3053 transistors should be mounted on suitable heat sinks and the current sense resistor should be rated at 3 watts or more. Voltage regulation is controlled by 1/2 of a 1558 or 1458 op-amp. The 1458 may be substituted in the circuit below, but it is recommended the supply voltage to pin 8 be limited to 30 VDC, which can be accomplished by adding a 6.2 volt zener or 5.1 K resistor in series with pin 8. The maximum DC supply voltage for the 1458 and 1558 is 36 and 44 respectively. The power transformer should be capable of the desired current while maintaining an input voltage at least 4 volts higher than the desired output, but not exceeding the maximum supply voltage of the op-amp under minimal load conditions. The power transformer shown is a center tapped 25.2 volt AC / 2 amp unit that will provide regulated outputs of 24 volts at 0.7 amps, 15 volts at 2 amps, or 6 volts at 3 amps. The 3 amp output is obtained using the center tap of the transformer with the switch in the 18 volt position. All components should be available at Radio Shack with the exception of the 1558 op-amp.

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Variable Voltage and Current Power Supply
Another method of using opamps to regulate a power supply is shown below. The power transformer requires an additional winding to supply the op-amps with a bipolar voltage (+/- 8 volts), and the negative voltage is also used to generate a reference voltage below ground so that the output voltage can be adjusted all the way down to 0. Current limiting is accomplished by sensing the voltage drop across a small resistor placed in series with the negative supply line. As the current increases, the voltage at the wiper of the 500 ohm pot rises until it becomes equal or slightly more positive than the voltage at the (+) input of the opamp. The opamp output then moves negative and reduces the voltage at the base of the 2N3053 transistor which in turn reduces the current to the 2N3055 pass transistor so that the current stays at a constant level even if the supply is shorted. Current limiting range is about 0 - 3 amps with components shown. The TIP32 and 2N3055 pass transistors should be mounted on suitable heat sinks and the 0.2 ohm current sensing resistor should be rated at 2 watts or more. The heat produced by the pass transistor will be the product of the difference in voltage between the input and output, and the load current. So, for example if the input voltage (at the collector of the pass transistor) is 25 and the output is adjusted for 6 volts and the load is drawing 1 amp, the heat dissipated by the pass transistor would be (25-6) * 1 = 19 watts. In the circuit below, the switch could be set to the 18 volt position to reduce the heat generated to about 12 watts.

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2 Watt Switching Power Supply
In this small switching power supply, a Schmitt trigger oscillator is used to drive a switching transistor that supplies current to a small inductor. Energy is stored in the inductor while the transistor is on, and released into the load circuit when the transistor switches off. The output voltage is dependent on the load resistance and is limited by a zener diode that stops the oscillator when the voltage reaches about 14 volts. Higher or lower voltages can be obtained by adjusting the voltage divider that feeds the zener diode. The efficiency is about 80% using a high Q inductor.

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Whistle On - Whistle Off

This is an extension of the CMOS toggle flip flop circuit shown in the "Circuits controlling relays" section with the addition of two bandpass filters and condenser microphone so the relay can be toggled by whistling at it. The condender mic used is a PC board mount Radio Shack #270-090C. The filters are tuned to about 1700 Hz, or the third Ab above middle C on a piano keyboard which is a fairly easy note for me to whistle. Resistor values for the filter can be computed using the three formulas below but we need to assume a gain and Q factor for the filter and the Q of the circuit must be greater than the square root of (Gain/2). The microphone produces only a couple millivolts so the overall gain needs to be around 4000 or around 65 for each filter. The Q or quality factor is the ratio of the center frequency to the bandwidth (-3dB points) and was chosen to be 8 which is greater than 5.7 which is the minimum value for a gain of 65. Both capacitor values need to be the same for easy computation of the resistor values and were chosen to be 0.01uF which is a common value and usable at audio frequencies. From those assumptions, the resistor values can be worked out from the following formulas.
R1 = Q/(G*C*2*Pi*F) = 8/(65*.01^-6*6.28*1700) = 1152 or 1.1K
R2 = Q / ((2*Q^2)-G)*C*2*Pi*F) = 8/((128-65)*.01^-6*6.28*1700)= 1189 or 1.2K
R3 = (2*Q)/(C*2*Pi*F) = 16/(.01^6*6.28*1700) = 150K

The op-amps are biased using a voltage divider of two 10K resistors so the output will be centered around half the supply voltage or 6 volts. The output of the second filter charges a 1uF cap at the base of a NPN transistor (2N3904 or similar). The emitter voltage is biased at 6.6 volts using the 3.3K and 2.7K resistors so that the transistor will conduct and trigger the flip flop when the peak signal from the filter reaches 8 volts. The 8 volt figure is the emitter voltage (6.6) plus the emitter base voltage drop (0.7) plus the diode drop (0.7). The sensitivity can be adjusted by changing the value of either the 2.7K or 3.3K resistors so that more or less signal amplitude is needed to trigger the flop flop.



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DC to DC Converter

The circuit below is a DC to DC converter using a standard 12 VAC center tapped power transformer wired as a blocking oscillator. The circuit is not very efficient but will produce a high voltage usable for low power applications. The input battery voltage is raised by a factor of 10 across the transformer and further raised by a voltage tripler consisting of three capacitors and diodes connected to the high voltage side of the transformer. The circuit draws about 40 milliamps and should operate for about 200 hours on a couple of 'D' alkaline batteries. Higher voltages can be obtained by reducing the 4.7K bias resistor. More information on blocking oscillators can be found here: Blocking Oscillators

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120 VAC Lamp Dimmer
The full wave phase control circuit below was found in a RCA power circuits book from 1969. The load is placed in series with the AC line and the four diodes provide a full wave rectified voltage to the anode of a SCR. Two small signal transistors are connected in a switch configuration so that when the voltage on the 2.2uF capacitor reaches about 8 volts, the transistors will switch on and discharge the capacitor through the SCR gate causing it to begin conducting. The time delay from the beginning of each half cycle to the point where the SCR switches on is controlled by the 50K resistor which adjusts the time required for the 2uF capacitor to charge to 8 volts. As the resistance is reduced, the time is reduced and the SCR will conduct earlier during each half cycle which applies a greater average voltage across the load. With the resistance set to minimum the SCR will trigger when the voltage rises to about 40 volts or 15 degrees into the cycle. To compensate for component tollerances, the 15K resistor can be adjusted slightly so that the output voltage is near zero when the 50K pot is set to maximum. Increasing the 15K resistor will reduce the setting of the 50K pot for minimum output and visa versa. Be careful not to touch the circuit while it is connected to the AC line.

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Varying brightness AC lamp
In this circuit, an SCR is used to slowly vary the intensity of a 120 volt light bulb by controlling the time that the AC line voltage is applied to the lamp during each half cycle.

Caution:

The circuit is directly connected to the AC power line and should be placed inside an enclosure that will prevent direct contact with any of the components. To avoid electrical shock, do not touch any part of the circuit while it is connected to the AC power line. A 2K, 10 watt power resistor is used to drop the line voltage down to 9 volts DC. This resistor will dissipate about 7 watts and needs some ventilation.

Operation:

A couple NPN transistors are used to detect the beginning of each half cycle and trigger a delay timer which in turn triggers the SCR at the end of the delay time. The delay time is established by a current source which is controlled by a 4017 decade counter. The first count (pin 3) sets the current to a minimum which corresponds to about 7 milliseconds of delay, or most of the half cycle time so that the lamp is almost off. Full brightness is obtained on the sixth count (pin 1) which is not connected so that the current will be maximum and provide a minimum delay and trigger the SCR near the beginning of the cycle. The remaining 8 counts increment the brightness 4 steps up and 4 steps down between maximum and minimum. Each step up or down provides about twice or half the power, so that the intensity appears to change linearly. The brightness of each step can be adjusted with the 4 resistors (4.3K, 4.7K, 5.6K, 7.5K) connected to the counter outputs.
The circuit has been built by Don Warkentien (WODEW) who suggsted adding a small 47uF capacitor from ground to the junction of the current source transistor (PNP) to reduce the digital stepping effect so the lamp will brighten and fade in a smoother fashion. The value of this capacitor will depend on the 4017 counting rate, a faster rate would require a smaller capacitor.



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oscillators

Inverter (logic gate)
From Wikipedia, the free encyclopedia
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For the electrical power inverter, see Inverter (electrical).

Static CMOS InverterIn digital logic, an inverter is a logic gate which inverts the digital signal driven on its input. It is also called NOT gate. The truth table of the gate is as follows:

The truth table for inverter input output
0 1
1 0

This represents perfect switching behavior, which is the defining assumption in Digital electronics. In practice, actual devices have electrical characteristics that must be carefully considered when designing inverters. In fact, the non-ideal transition region behavior of a CMOS inverter makes it useful in analog electronics as a class A amplifier (e.g., as the output stage of an operational amplifier[1]).

Contents [hide]
1 Electronic implementation
1.1 Performance measurement
1.2 Digital building block
1.3 External links
1.4 References



[edit] Electronic implementation

Schematic of a Saturated-Load Digital InverterAn inverter circuit outputs a voltage representing the opposite logic-level to its input. Digital electronics are circuits that operate at fixed voltage levels corresponding to a logical 0 or 1 (see Binary). An inverter circuit serves as the basic logic gate to swap between those two voltage levels. Implementation determines the actual voltage, but common levels include (0, +5V) for TTL circuits.

Common types include resistive-drain, using one transistor and one resistor; and CMOS, which uses two (opposite type) transistors per inverter circuit


[edit] Performance measurement
Digital inverter quality is often measured using the Voltage Transfer Curve, which is a plot of input vs. output voltage. From such a graph, device parameters including noise tolerance, gain, and operating logic-levels can be obtained.


Voltage Transfer Curve for a 20 μm Inverter constructed at North Carolina State UniversityIdeally, the voltage transfer curve (VTC) appears as an inverted step-function - this would indicate precise switching between on and off - but in real devices, a gradual transition region exists. The VTC indicates that for low input voltage, the circuit outputs high voltage; for high input, the output tapers off towards 0 volts. The slope of this transition region is a measure of quality - steep (close to -Infinity) slopes yield precise switching.

The tolerance to noise can be measured by comparing the minimum input to the maximum output for each region of operation (on / off).

The output voltage, VOH, can be a measure of signal driving strength when cascading many devices together.


[edit] Digital building block
The digital inverter is considered the base building block for all digital electronics. Memory (1 bit register) is built as a latch by feeding the output of two serial inverters together. Multiplexers, decoders, state machines, and other sophisticated digital devices all rely on the basic inverter.

The Hex Inverter is an integrated circuit that contains six (hexa-) inverters. For example, the 7404 TTL chip and the 4049 CMOS chip each have 14 pins, 2 of which are used for power/referencing, and the remaining 12 pins are used by the inputs and outputs of the six inverters.

inverter project design

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DC to AC power inverters
Power or electrical energy is usually stored in batteries. Batteries can only give Direct Current (DC) and not Alternating Current (AC).



DC AC power inverter

So, the problem arises when you need to take power that has been stored in a battery or bank of batteries, and use it to run electrical appliances that are AC and not DC.

The answer to this, is to use a DC to AC power inverter.

The inverter is the main component of any independent power system which requires AC power. The power inverter will convert the DC power stored in the batteries and into Ac power to run conventional appliances.



Inverters

Just over a decade or so ago, DC AC power inverters were so inefficient and unreliable, many people restricted themselves to 12V lights and appliances.

If you have recently tried to shop around for 12V DC appliances, you will see that there is a very limited selection available.

Today, the efficiency and reliability of the latest DC AC power Inverters, are a far cry from the inverters that were available 15 to 20 years ago.

There are three waveforms produced by modern solid state power inverters. The simplest, a square wave power inverter, used to be all that was available. Today, these are very rare, as many appliances will not operate on a square wave.

For ease of reference, we have categorized our comprehensive DC to AC power inverter range into into simple subheadings that should make it a lot easier for you to find the specific size, type and rating of power inverter to suit your specific need and application:

Modified sine wave power inverter
Pure sine wave power inverter
Power inverters for 4x4
Power inverters for laptop
Backup inverter power for your home
Backup inverter power for your office
Solar inverters
Inverters with generator transfers
If you would like to know more about the types of DC to AC power inverters available today, click on either “modified sine wave” or “true sine wave” button to find out all you can about our DC AC power inverters.

Keywords for this page:

Inverter, Inverters, Power inverter, power inverters



Copyright © 2005 - 2007 Plan-My-Power (PTY) ltd

Inverters

What is an inverter?
How does an inverter work?
Why are most inverters are 115 volts
What size wire, fuse, or breaker will I need?


What is an inverter?
An inverter changes DC voltage from batteries or solar panels, into standard household AC voltage so that it can be used by common tools and appliances.

Converters: What are sometimes called "converters", especially in the RV world, are actually battery chargers and/or DC power supplies. Why they are called converters in RV's and no place else we have not a clue. A "converter" is basically the opposite of an inverter.

Essentially, it does the opposite of what a battery charger or "converter" does. DC is usable for some small appliances, lights, and pumps, but not much else. Most systems should include an inverter of some type, even if it is just an el-cheapo $29 Walmart thing to run the TV occasionally. Some DC appliances are available, with the exception of lights, fans and pumps there is not a wide selection. Most other 12 volt items we have seen are expensive and/or poorly made compared to their AC cousins. The most common battery voltage inputs for inverters are 12, 24, and 48 volts DC - a few models also available in other voltages.

There is also a special line of inverters called a utility intertie or grid tie, which does not usually use batteries - the solar panels or wind generator feeds directly into the inverter and the inverter output is tied to the grid power. The power produced is either sold back to the power company or (more commonly) offsets a portion of the power used. These inverters usually require a fairly high input voltage - 48 volts or more. Some, like the Sunny Boy, go up to 600 volts DC input.

A few grid tie inverters can also be used with batteries, but there will be some loss in overall efficiency for feeding the grid. How much loss can vary considerably, depending on the inverter and the size and type of batteries. If you need battery backup power for a grid tie system, we recommend the Outback Power inverters, as they have the best efficiency with batteries - you will get about a 5-10% loss. With some older inverters, such as the Xantrex SW series, that can sell back excess power to the grid overall losses can be as high as 50%.

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How does an inverter work?
An inverter takes the DC input and runs it into a pair (or more) of power switching transistors. By rapidly turning these transistors on and off, and feeding opposite sides of a transformer, it makes the transformer think it is getting AC. The transformer changes this "alternating DC" into AC at the output. Depending on the quality and complexity of the inverter, it may put out a square wave, a "quasi-sine" (sometimes called modified sine) wave, or a true sine wave.

Square wave inverters are usually only suitable for running some type of electrical tools and motors and incandescent lights. They are pretty rare nowadays, some of the old 1970's Triplite and a few others, and some old military surplus is about the only place you find it now.

Quasi-sine (modified sine, modified square) wave inverters have more circuitry beyond the simple switching, and put out a wave that looks like a stepped square wave - it is suitable for most standard appliances, but may not work well with some electronics or appliances that electronic heat or speed control, or uses the AC for clocks or a timer.

What May Not Run: Appliances that use electronics to control temperature or timers may have problems with modified sine waves. This includes anything - tool or appliance - that is variable speed, bread makers, some microwaves, some washers and dryers that use electronic timing for cycling. Most computers, TV's and similar items will have no problem. Anything with a motor will use about 20% more power with a modified sine wave than with a true sine wave.

Also, some of the chargers used for battery operated tools (such as Makita) may not shut off when the battery is charged, and should not be used with anything but sine wave inverters unless you are sure they will work. Sine wave inverters put out a wave that is the same as you get from the power company - in fact, it is often better and cleaner. Sine wave inverters can run anything, but are also more expensive than other types. The quality of the "modified sine" (actually modified square wave), Quasi-sine wave, etc. can also vary quite a bit between inverters, and may also vary somewhat with the load. The very bottom end put out a wave that is nothing but a square wave, and is too "dirty" for all but universal motor driven tools, coffee makers, toasters, and other appliances that have only a heating element.

One solution to the problem of a few small appliances not working well with modified sine wave inverters is to get a large standard inverter, and a small (such as the Exeltech or Samlex) true sine wave for use only with that equipment. This would also allow you to keep the small appliance (such as an answering machine) powered up without having to run the larger inverter full time.

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Why are most inverters 115 volts?
Most utility connected homes in North America have dual AC voltages - 115 and 230. On a typical home there are three wires coming in - 115-neutral-115. It is 230 volts across the two outside ones. The 115 is used for most things, while 230 is used for water heaters, electric clothes driers, well water pumps, and air conditioning. Since these high-power items are not practical in a solar powered home, they are either not used or are replaced with gas appliances.

Most off-grid homes have little use for 230 volt AC power - but even so many newer ones are wired just like a standard home to meet electrical and building codes. If it IS required, you can "stack" two 115 volt inverters to get 230. The one exception to the above is that many AC well pumps are 230 volt. If the well pump is the only 230 volt item you have, the best choice is probably to get a step up transformer, such as the Xantrex or Outback Power 120 to 240 step up transformer.

There are export versions of most inverters for 100 volts, 105 volts, 205 volts, and 220/230 volts, in both 50 and 60 Hz.

Inverter-Chargers:
Inverters come in two basic types - with and without built in battery chargers. The ones with built in chargers are handy if you charge your batteries from AC, especially for RV's. They are also essential if using an inverter for setting up a UPS system for backup power. But not everyone needs them - and most small inverters under 1000 watts or so are simply not available with a built in charger.

Nearly all inverter-chargers made in the past few years have 3-stage chargers, so you can usually leave them powered up all the time. Nearly all inverters with chargers also have a built in transfer relay - what that means is that if you are running from AC or shore power, the power feeds through the inverter, with some being tapped off for the battery charger. If the AC power goes out, the inverter automatically switches to battery power. In most cases you won't even see a light flicker, it is so fast.

Inverter (and other) Efficiency:
Inverter efficiency is a question we get asked about a lot. The efficiency of an inverter has to do with how well it converts the DC voltage into AC. This usually ranges from 85% to 95%, with 90% being about average.

However, there is more to the story. Efficiency ratings are usually given into a resistive load (basically something like a light bulb or electric heater). When running such things as motors, the efficiency actually breaks down into two parts - the efficiency of the inverter, and the efficiency of the waveform. Waveform efficiency means that most motors and many electronic appliances run better and use less power with a sine wave. Typically, an electric motor (such as a pump or refrigerator) will use from 15% to 20% more power with a modified sine wave than with a true sine wave. When choosing an inverter based on efficiency, you should also consider what you are going to be running.

A 90% efficient modified sine wave inverter is not 90% when running a compressor motor, for example, because electric motors are less efficient. They use about 20% more power on a modified sine wave.

Inverters are also much less efficient when used at the low end of their maximum power. For example, using a 1000 watt inverter to power a 20 watt radio may actually be using 30 to 40 watts from the battery, as the inverter itself is eating up a lot just to run. Most inverters are most efficient in the 30% to 90% power range.

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What size wire, fuse, or breaker will I need?
Inverters have two or three sets of power carrying wires to be concerned about: the wires from the battery to the inverter, the wires from the inverter to the home (or other AC load), and in some cases the wiring from a backup generator or other AC source. The wiring for the AC to the home and from the generator is sized just like you would for AC wiring in a utility connected home. It is usually #10, 12, or 14 standard AC wire. For the small inverters, 800 watts or less, #16 can be used but the mechanical strength of small wire leaves much to be desired.

The wire or cables from the batteries to the inverter are much more critical, and are often undersized. In some cases, the cable may be large enough to carry the "static" load of a motor, but on start up will drop so much voltage in the cable that the inverter will shut down on low voltage cutoff. The same thing can happen with small inverters and TV sets - a TV may only use 100 watts, but the start up surge may be 300 watts for a few seconds. Wire lengths from the battery should always be kept as short as possible, but not so tight that there is a strain on the connections.

Recommended Fuses, Breakers, and Wire Sizes for Inverters
Inverter Watts Inverter DC voltage Input Fuse/Breaker DC Wire Size
Minimum !
50-150 12 20 amp 12 to 14
200-250 12 30-40 amp 8 to 10
300-500 12 50-60 amp 6 to 8
600-1000 12 110 amp 4 to 6
1100-1500 12 200 amp/175 bkr 2/0 to 2
1100-1500 24 110 amp 2/0 to 4
1800-2500 12 300 to 400 amp/250 4/0
1800-2500 24 200 amp/175 2/0
2600-3600 24 400 amp/250 4/0
4000 24 400 amp/250 4/0
4000 48 200 amp/175 2/0
5500 48 200 amp/175 2/0

These are the recommended cable sizes for a ten-foot distance from the batteries to the inverter. Note that the larger wire size is the recommended, the smaller wire size is the absolute minimum for safe operation. The sizes recommended are from a combination of maximum wire amperage capacity and voltage drop. You can't go wrong using bigger wire.

The fuse and breaker sizes shown are approximate. Since transformer based (Outback Power, Xantrex) inverters usually have a much higher maximum surge rating than electronic based (Samlex, Exeltech, Statpower), they should always use the larger if more than one size is shown. The reason some show a smaller breaker size than fuse size is that breakers do not blow as fast on a temporary surge.

The fuse should NEVER be bigger than 125% of the maximum surge power of the inverter. For example, an inverter is rated at 1000 watts, and 1800 watts surge. For a 12 volt inverter, divide 1800 by 12, which gives you 150. 150 x 1.25 = 190 amp. The nearest standard size fuse is 200 amp. You are always safe going to a smaller fuse, but if too small it might blow on heavy loads. DC breakers should be rated for about the maximum amperage draw, as they have a slight time delay on over current.

Which inverter has the best sine wave?
In general, from best down, it is Exeltech, Outback Power, Statpower, Samlex. All are good enough for 99% of all applications, but the Exeltech may be better for low power critical applications, such as recording or studio vans, or noise sensitive medical equipment. For higher power systems that need the best sine wave, either the Outback Power series or the Xantrex SW+ series.

Which is the "best" inverter?
There is no "best" for all purposes. Although the Outback Power & Xantrex are considered by many to be the top of the line, it does not make sense to spend $500 to $3000 when all you need is a little Statpower Prowatt or Exeltech 125 watt sine wave to power up a laptop. The best way to decide on what inverter is best is to work backwards - figure out what you are going to use it for, and then find one that fits those requirements. Also, some inverters have built in chargers, which may be needed in some systems. The Outback & Xantrex sine wave units include software and hardware for remote generator start, alarms, remote control and monitoring, computer data, and other functions - in many applications this is very important. If you are running pumps or other large motors, Xantrex or Outback are the only one we will recommend, even though some others might work.

Inverters

Michael Inverter Circuits

View my inverter circuits and please give me a feed back

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