Are Pure Sine Wave Inverters Really Possible?

Of course it's possible.

yep

Your flaw in thinking is that an inverter must be only a switch.

A simple Google search lists about 1,020,000 results saying yes, it is really possible.

Google Search - Wikipedia, the free encyclopedia

how does google work

I know how googles work!!!! Still no help I have really cool set googles

Then use Google and search for 'Dork Goggles'. Same image.

Flaw #2 is in thinking the output is a square wave. 30 years ago, maybe, but the world has moved on. Look at the concept of "Pulse Width Modulation" and "sine wave filtering" as it relates to that.

Pure wave sign....

Sine wave inverters are very simple to understand. The DC is fed to a sort of variac with a center off lever control . The lever is controlled by the force applied to it both in direction of low and intensity of flow. This is all difficult to see since it has a cage like enclosure. Inside this there is a little critter who jumps up and down with a pogo stick. All this is connected to an outlet panel with several sockets on it. The more power wanted, the more critters you use in this device.

Good Luck, Old Salt

What is this?

Posi-VAC system for addressing erectile dysfunction?

It's obviously a square wave to sine wave converter...see how smooth every thing is?

It is obviously a critter enema-izer. Required if they make sloppy sine waves.

Good Luck, Old Salt

Something only legal to use in Washington and Colorado?

You are on the right track.

Re-constitued AC waveforms are not a "pure" sine wave by any sense of the imagination and contain harmonics, noise, gaps in waveform. etc.

However; filtering allows the effective value of the waveform to meet/satisfy the circuit requirements if the inverter design is matched to the load application.

Your premise, 'As it is just a switch,' is false, as your question, 'how are there pure sine-wave inverters?' acknowledges and given that there *are* sine-wave inverters, then your question answers itself.

Inverters do not convert rectangular AC to sinusoidal AC as a rule. Some inverters approximate a sine-wave using diode networks whilst many modern inverters synthesize a sine wave directly then amplify it. There are other techniques as well, some using ferroresonant transformers, for instance.

Yes, they are. Start with whatever you have, convert it to DC at a suitable voltage (~180 if you want a 120VAC RMS sine wave) then put it through an H bridge with a PWM into an inductive filter, (your basic class D amplifier) and there you go. Adjust the filtering until it's as pure as you need it to be. Yes, it is a switcher and yes it is a sine wave output.

Using DC to get a pure sine wave. Sure its possible but very inefficient. Just use the DC to run a motor that turns an AC generator. As I say, it is a very inefficient way to do it. It can be done electronically but will not be absolutely pure though certainly close enough for most uses.

Not inefficient at all. If you have ~80% efficiency on the DC motor and 60% on the alternator you end up with 48% overall. A class D converter can easily hit 80% or better and with modern circuits it isn't very complex. Most of the functions are highly integrated. I could do it with about 2 integrated circuits and a mosfet power bridge. It really is no big deal.

http://www.cumminspower.com/www/common/templatehtml/technicaldocument/SpecSheets/Diesel/na/s-1375.pdf

Typical rotary (mechanical) generator: Total Harmonic Distortion max. 5%

Inverters: typ. THD 3% or less.

What is a "pure sine wave"?

Look at the waveform from the nearest power outlet...

How do you measure(unit/factor)purity of a sinewave?. For each of the applications like incandescent(led/cfl/induction/liner flourescent/mercury/sodium/halogen) lights, TV,radio,computer,induction motoretc what kind of waveform is acceptable?.

That's an essay question.

Can you give a link/website/code which gives it.

Need to do filtering, a washout filter will do. Selecting filter coefficients will need computer program- Matlab to find a improved sine waveform using equations. The dignity of the final waveform will be decided by the harmonic content and dc offset.

__+---

One does not need a computer for good filter design.

How much harmonic content & how much DC offset is allowed for each application like incandescent/led/cfl./lfl/sodium/mercury/induction lighting,TV,computer, induction motor,radio etc?.Give a link or standard/code.

The cheap inverters have an almost "square" wave output and a square wave ( if memory serves me right) is composed of all the odd harmonicas of the frequency....which is probably why sensitive electronic equipment does not like cheap inverters!

There are inverters available to buy with a so called true (if digital!) sine wave output, that have far fewer harmonics.....but usually cost more, like double I believe, and I am told, also less efficient....

There is a device that consists of a sealed black box to which a rod consisting of segments of dashes and longer pieces is inserted into what is to be considered a inlet port. After a length of time and various mechanical noises, a wavy-shaped rod emerges from the opposing end. This wavy shaped rod is perfect in symmetry.

This rod is then incorporated into a device used for testing hand/eye co-ordination.

Let's not forget the Fourier Theorem that states that any periodic waveform maybe expressed as the sum of a collection of sine and cosine functions.

Look up class D amplifiers.

A common inverter switches 2 times for each cycle, at best approximating the RMS power into a resistive load of a sine wave. A class D type inverter will switch up to >100k times for each cycle and filter the result into a sine wave with defined distortion and noise parameters. These are readily available as finished products or you can build your own using any of a surprising number of offerings by IC manufacturers.

Good Luck...............