Is an actual true sine wave inverter possible?

[Shadow_Storm56]

I am curious, is it actually possible to have a true sine wave inverter for real or is a true sine wave inverter, even really high end ones used in off grid homes just an inverter with a much larger amount of steps to give an essentially pure sine wave? or is there actual circuitry that is in high end inverters that will allow to creation of a perfect sine wave that would match that of the grid?

[vanished]

If you're asking is it possible to create a mathematically perfect sine wave, then I'd say no for a variety of reasons, but for all intents and purposes, yes, you can create extremely good ones that would have no practical difference.

[Shadow_Storm56]

1 hour ago, James Evens said:

Even with analog technology you don't get perfect waveforms. There is always a thing called distortion you can measure.

Fair point, 

 

2 hours ago, Ryan_Vickers said:

If you're asking is it possible to create a mathematically perfect sine wave, then I'd say no for a variety of reasons, but for all intents and purposes, yes, you can create extremely good ones that would have no practical difference.

So if generated power by grid sources and inverter power are slightly different couldn't you pick them out on an ossioscope? Like if you were next to a solar farm for example. You could see the stepped wave form mixed with the smooth? Or are the steps so small that it would all just blend together ?

[vanished]

11 minutes ago, Shadow_Storm56 said:

So if generated power by grid sources and inverter power are slightly different couldn't you pick them out on an ossioscope? Like if you were next to a solar farm for example. You could see the stepped wave form mixed with the smooth? Or are the steps so small that it would all just blend together ?

If you zoomed in enough you'd see noise or other abnormalities in anything, but on any good equipment, they're well, "within the noise" - ie, such small imperfections that it doesn't matter and for all intents and purposes it's considered perfect.

[Shadow_Storm56]

5 minutes ago, Ryan_Vickers said:

If you zoomed in enough you'd see noise or other abnormalities in anything, but on any good equipment, they're well, "within the noise" - ie, such small imperfections that it doesn't matter and for all intents and purposes it's considered perfect.

So its would be so small you wouldn't be able to find the stepped waveform amongst the fine noise. I guess other buddy is right as well, even generated power will have noise as nothing is perfect. Cool thanks for the info 

[vanished]

4 minutes ago, Shadow_Storm56 said:

So its would be so small you wouldn't be able to find the stepped waveform amongst the fine noise. I guess other buddy is right as well, even generated power will have noise as nothing is perfect. Cool thanks for the info 

I don't mean to imply that every sine wave is made "digitally" and would consist of tiny steps, just so that's clear

[Canada EH]

3 hours ago, Shadow_Storm56 said:

I am curious, is it actually possible to have a true sine wave inverter for real or is a true sine wave inverter, even really high end ones used in off grid homes just an inverter with a much larger amount of steps to give an essentially pure sine wave? or is there actual circuitry that is in high end inverters that will allow to creation of a perfect sine wave that would match that of the grid?

Nothing requires a true sinewave!

[Hackentosher]

9 hours ago, Canada EH said:

Nothing requires a true sinewave!

Agreed. Most household electronics are completely rectifier based, so they can run on messy AC, or even DC. Just last week I watched a dell 1440p monitor turn on and function as normal on 100v DC. That being said, some things do require AC like inductance motors, but anything self commutating or with a rectifier can run on both.

[Canada EH]

Agreed but not absolutely pure sinewave. Close enough is good enough!

[Blasteque]

18 hours ago, Shadow_Storm56 said:

I am curious, is it actually possible to have a true sine wave inverter for real or is a true sine wave inverter, even really high end ones used in off grid homes just an inverter with a much larger amount of steps to give an essentially pure sine wave? or is there actual circuitry that is in high end inverters that will allow to creation of a perfect sine wave that would match that of the grid?

As for achieving this electrically with a cheap box you can plug into your cigarette lighter, no.  And it rarely matters.

 

However, you absolutely can have a true sine wave by using a mechanical inverter (or rotary converter https://en.wikipedia.org/wiki/Rotary_converter ).  The simplest form is a DC motor that drives an alternator.  When you think about it, it's actually pretty obvious.  Electroboom shows a simple 3 phase inverter he made in this video (around the 9 minute mark):

 

[Shadow_Storm56]

17 minutes ago, Blasteque said:

As for achieving this electrically with a cheap box you can plug into your cigarette lighter, no.  And it rarely matters.

 

However, you absolutely can have a true sine wave by using a mechanical inverter (or rotary converter https://en.wikipedia.org/wiki/Rotary_converter ).  The simplest form is a DC motor that drives an alternator.  When you think about it, it's actually pretty obvious.  Electroboom shows a simple 3 phase inverter he made in this video (around the 9 minute mark):

 

I did not think of that, although running a DC motor to an ac generator seems like it would be less efficient than an inverter as all that mechanical loss. 

 

16 hours ago, Ryan_Vickers said:

I don't mean to imply that every sine wave is made "digitally" and would consist of tiny steps, just so that's clear

Oh I know that just the digital sine waves are steppy not all sine waves.

 

2 hours ago, Canada EH said:

Agreed but not absolutely pure sinewave. Close enough is good enough!

I think a real true sine wave inverter is just saying closer to real and in the high quality ones the number of steps and configuration allows the output power to match the effect of generated power.

[Blasteque]

2 minutes ago, Shadow_Storm56 said:

I did not think of that, although running a DC motor to an ac generator seems like it would be less efficient than an inverter as all that mechanical loss. 

Yes, using a motor to turn an alternator is not particularly efficient, but it is a simple to understand example.  Purpose built rotary converters worked differently.  Although they made a perfect sine wave, they are now obsolete, because close enough is good enough.

 

The problem with consumer inverters is they use the simplest and crappiest of techniques (because it's cheap).  On a commercial or industrial scale electrical inverters are actually pretty good and the noise in the line often completely conceals the steps. https://en.wikipedia.org/wiki/Power_inverter

[2FA]

18 minutes ago, Blasteque said:

Yes, using a motor to turn an alternator is not particularly efficient, but it is a simple to understand example.  Purpose built rotary converters worked differently.  Although they made a perfect sine wave, they are now obsolete, because close enough is good enough.

 

The problem with consumer inverters is they use the simplest and crappiest of techniques (because it's cheap).  On a commercial or industrial scale electrical inverters are actually pretty good and the noise in the line often completely conceals the steps. https://en.wikipedia.org/wiki/Power_inverter

The sine wave will never be perfect except in mathematics due to noise. Background EMI is enough to disrupt it to no longer consider it perfect. If you're talking theoretical, then sure an alternator would create a perfect sine wave but practically it will not.

[Blasteque]

Just now, 2FA said:

The sine wave will never be perfect except in mathematics due to noise. Background EMI is enough to disrupt it to no longer consider it perfect. If you're talking theoretical, then sure an alternator would create a perfect sine wave but practically it will not.

Of course, but the issue being discussed in context is not theoretical perfection, only "pure" sine wave versus discreet stepping.  You're right that "perfect" was not the correct term, apparently the technical term used in the industry is "pure".

 

The problem on the table here is the creation or recreation of AC power is if it were coming out of a wall-socket.  In that regards turning an alternator could be just as "pure" (or perfect) as what your local power plant is producing (if they're making AC power natively).  I'll try to be more careful with my wording next time.

[porina]

This thread almost makes me want to (somehow) hook up mains electricity to a test system at work to look at more closely. Without having done so, I'm willing to bet the purity of the power by the time it reaches a home isn't that great. It will be distorted by the various devices attached taking power in a non-linear way. There are standards on appliances in how they take power to minimise this.

[Shadow_Storm56]

1 hour ago, porina said:

This thread almost makes me want to (somehow) hook up mains electricity to a test system at work to look at more closely. Without having done so, I'm willing to bet the purity of the power by the time it reaches a home isn't that great. It will be distorted by the various devices attached taking power in a non-linear way. There are standards on appliances in how they take power to minimise this.

May be a fun experiment. Some places do have bad noise and some have weird voltages so who knows. Overall things are consistent but it's a fun experiment to see how things are

[JokerProduction]

I just so happen to have a 1000V scopemeter so here are some captures.

 

At the Wall

 

 

Off the inverter of cyberpower PFC 1800

 

 

 

Seems pretty good for a sub 300$ ups.  There is more noise at the peaks and the peak actually shifts forward on the UPS.  Im sure this waveform would not be any issue for most loads.

[JokerProduction]

Heres some other captures I had when I was messing around with a triac based dimmer and different loads. Figured someone might find this interesting.  A input is supply power and the B input is the load.  B input is also half scale and offset down 1 unit 

 

 

[Shadow_Storm56]

Nice, idk alot about reading scopes but cool either way. What's going on with the dimmer bulbs? Noise? I see 2 sets of lines with one being jagged.