Pure sine wave inverters

[SolarCity]

I wonder if anyone has used any pure sine wave inverters - or even knows of any that are G83 certified? I have a potential customer that is keen on one if such a thing exists.

I have checked the sine wave of an SMA inverter at a previous customer's house on an oscillator and the sine wave was very good. Therefore I'm not convinced it would be an issue but it would interesting to see if anything is about.

 

[jason121]

Can you explain a little more, bit over my head

 

[Steve_rutland]

I have a 1kw Mascot pure sine on my off grid. Got it mainly as a standard inverter didn't like running tube lights.

 

[yorkshiremike]

I thought that all the grid tied (G83) inverters are true/pure Sine output (at least as good as the grid), it's just that they need the grid to be there (and within specification) to output.

 

[jason121]

Just found this
A grid-tie inverter has to be a pure sine inverter that also does all this:

1. match the phase of the sine-wave to the grid
2. match the voltage of the sine-wave to the grid.
3. match the freqency of the sine-wave to the grid.

To do all 3 of those makes it more expensive. It's not marketing hype, it's extra circuitry to do all of that stuff.

If you just throw a plain sine-inverter on the grid and you aren't matched to all three (voltage, phase, frequency), your sine-inverter will burn up very quickly, possibly in a righteous display of melted metal and sparks.

 

[Gavin A]

yes, all grid tie inverters are pure sine wave - the only ones that aren't are some of the more basic off grid inverters that are stepped or modified sine wave and only suitable for a few purposes - certainly not powering a PA at a festival, as we learnt one time back in the 90s when this was all very knew to me.

 

[grantr37]

I wonder if anyone has used any pure sine wave inverters - or even knows of any that are G83 certified? I have a potential customer that is keen on one if such a thing exists.

I have checked the sine wave of an SMA inverter at a previous customer's house on an oscillator and the sine wave was very good. Therefore I'm not convinced it would be an issue but it would interesting to see if anything is about.

did you mean Oscilloscope?

 

[grantr37]

yes, all grid tie inverters are pure sine wave - the only ones that aren't are some of the more basic off grid inverters that are stepped or modified sine wave and only suitable for a few purposes - certainly not powering a PA at a festival, as we learnt one time back in the 90s when this was all very knew to me.

a rough equivalent sine wave generated as a kind of ramped trellice, it's stepped squarewaves, not really a sinewave at all.....very cheap to manufacture in fact you can build the circuit used in a cheap inverter for about £20 as opposed to the one in a pure sinewave of similar output that would come in at about £90 manufacture cost....the higher the output the bigger the increase in price difference...


i.e 1500 watt ramped square purchase price £100.00
or a 1500 watt pure sinewave purchase price £600.00, this one won't obliterate your electrical goods, the other one is only good for cheap radios and lights, maybe a cheap TV in a Caravan....

 

[Earthstore]

A little over my head but do you get a true sine wave from an inverter?
I thought that inverters produced an electrically modified sine wave, they are all stepped however the better quality inverters produce a sine wave that is grid compatible.
A true sine wave is produced by rotating energy, ie a generator.

 

[SolarCity]

My thinking was along the same lines as Earthstore. I thought that inverters generally produced a modified sine wave which could be problematic with some equipment.

And yes, I did mean oscilloscope.

 

[grantr37]

A little over my head but do you get a true sine wave from an inverter?
I thought that inverters produced an electrically modified sine wave, they are all stepped however the better quality inverters produce a sine wave that is grid compatible.
A true sine wave is produced by rotating energy, ie a generator.

A True Clean Sinewave can be easily generated using Electronics, it's just that the kind of components needed to generate a high current source cost a lot of money, there is also control circuitry to maintain the waveform to a constant bounded by certain maxima and minima when under load conditions....

That's why true sinewave inverters are so expensive (well along with a bit of over-pricing because they know that they are better and more in demand in the shops)


cheapo inverters from supermarkets and hobby stores produce what people generally refer to as a modified sinewave output...

 

[Earthstore]

Power inverter - Wikipedia, the free encyclopedia
Not sure if this link will work, Inverters can get within 3% of a true sine wave, which I suppose is close but it is still not a pure sine wave, just a compatible one.

 

[grantr37]

yes and the mains gets to about within 3% of a "perfect" sinewave as well....

 

[grantr37]

That 3% quoted on there is the THD total Harmonic Distortion as a percentage of the function of the waveform.....that's better than a lot of Audio Amplifiers...i.e the signal to noise ratio of the waveform...

 

[Vegelen]

Interesting article on inverter topologies including sine wave:

https://homepower.com/articles/how-inverters-work

 

[Earthstore]

Don't really know why I want to learn more about all this, guess I just do really.

Thank's, very interesting article, especially the part about not grounding the array on a TL inverter (that old chestnut).

I do wonder though how good the sine waves are from some of the inverters that have been installed, only time will tell I guess when sine wave sensitive electrical items start to fail on a regular basis, still, more work for sparkies I suppose.

 

[grantr37]

installed a load of these in Data centres and industrial a few years ago...

Three-phase UPS system 250-800 kVA | Chloride 90-NET | Emerson Network Power


took 3 days to commission and set up.....they put off a lot of heat into the rooms and needed constant aircon...

 

[Earthstore]

installed a load of these in Data centres and industrial a few years ago...

Three-phase UPS system 250-800 kVA | Chloride 90-NET | Emerson Network Power


took 3 days to commission and set up.....they put off a lot of heat into the rooms and needed constant aircon...

They look like some serious pieces of kit, if I understand correctly they stabilize sine wave, voltage etc.

 

[grantr37]

They look like some serious pieces of kit, if I understand correctly they stabilize sine wave, voltage etc.

£300,000 odd for 2 small rooms and a Battery room.....I was only the person who had to drag them in, re-assemble them and connect them up, on a very basic wage ......the labourers working for the UPS sales company came along later in the week and lugged in 4 forklift pallets of heavy Batteries, then somebody from the Battery company came in and tagged them all together, left the main DC switch padlocked off with the main fuses for it lying on the floor beside....UPS company came in to commission them and I got dragged into that as well.... When they arrived in a Lorry from the suppliers it was 3 in the afternoon on a Friday, pouring with Rain and getting dark in winter.....everybody thought they were for the pub then this sidecurtain opens on the Lorry and a manager turns up and says "this stuff has to go inside straight away.......cardboard and bubble wrap gets ripped off and it's the UPS units.....sat on the mud on a site with no roads and open cable and drainage trenches everywhere...took about 15 people to bump them along and inside.... When the giant switch cabinets and DB's arrived in from Ireland, they were so heavy and some 3 and 4 meters wide that we had to put them in with mm to spare via a service exit on the other side of the site from where they got dumped by the delivery company using a Telehandler ...then figure out how to get them to the other side of the building with a suspended floor mid process of going in....which involved a specially bodged up/welded steel scaffold with wheels from an alloy tower stuck onto it and about 12 people wheeling it around the outside of the building...

 

[Earthstore]

It sounds like it would have been easier to have built another Stonehenge, the stones only came from Wales....