Which PV Inverter has the best AC Waveform?

[phase1]

Hi, I wonder if any expert on this forum can advise me as to which of the generally-available inverters has the best,least choppy AC waveform? I know that a Pure Sine Wave inverter is the ideal but in practical terms they are prohibitivley expensive..Of the Modified Sine wave Inverters I read somewhere that the SMA Series had the nearest approach to pure AC..All the specs are very coy about this subject, I just wondered if anyone has seen some Oscilloscope traces of the various inverters-SMA, Fronius DIEHL, etc..I'm considering a PV installation ,but as I'm a Hi-Fi enthusiast,I don't want my music overlaid with a lot of Square Wave interference..I'm sure someone can give me some advice, or let me know of any complaints they've had about inverter interference..Many Thanks,Ron.:stooge_curly:

 

[Marvo]

If you're looking for an inverter to run Hi-Fi equipment then avoid all modified sine models. Some may be a marginally cleaner waveform than others but this won't help when it comes to high-end audio/visual equipment. Pure sine may cost more but you get what you pay for in this particular case.

 

[phase1]

Thanks Marvo.The inverter will be part of a normal domestic installation.I wondered if anyone has experience of a new inverter technology used by Mitsubishi,called "Gradationally Controlled Voltage" which ,while not pure sine wave, gives a much improved waveform,and would seem to be suitable for my needs..Many Thanks,Ron.

 

[Marvo]

I'm not in the PV industry so I couldn't comment on the latest technologies I'm afraid. I'm sure somebody in the know will advise you shortly. Just out of interest what's the price difference between the "Gradationally Controlled Voltage" system and the equivalent pure-sine system?

 

[phase1]

Unfortunately,I'm not sure about the cost.I saw it on a site entitled "Mitsubishi research and development" from 2010,so I don't know if they are available yet.I'm making enquiries and will let you know if I discover anything. I should imagine the cost would be somewhere between the Modified Sine and the Pure Sine prices.

 

[jerriais]

Hi Ron,

I have been doing a bit of research on this myself and will get back to you with some info shortly.

Matt

 

[LightGEN]

In all likeliness your HiFi equipment contains a power supply unit (PSU), which converts incoming 240V AC to DC, at a range of lower voltages to supply the electronics within. In the case of equipment which consumes modest amounts of power the PSU may be switched mode, which tend to be somewhat 'noisy' anyway. Items like large, better quality, audio amplifiers likely contain good sized linear PSUs with large 'audio quality' smoothing capacitors. I suspect, in either case, that the level of 'noise' on incoming AC supply has little direct effect on what comes out on the DC side of the PSU. I'd be interested in hearing alternative views.

As someone who's interested in Amateur Radio, my biggest concern is with Radio Frequency Interference (RFI), which can be radiated through any of the cables connected to the inverter. Based on experience with my own home installation and on an installation we've recently performed, SMA inverters produce no noticable 'noise' on the parts of the radio spectrum which we checked - in the case of the recent installation, clip-on ferrite chokes were added to the individual AC oupput cables and to each DC cable, just to be sure.

I recently read an article on the subject of RFI, in a radio communications periodical, which made it clear that some inverters are problematic in terms of RFI - PV system installers need to be aware of the potential for such problems and that they may be called on by Ofcom to resolve issues relating to RFI.

 

[daytona600]

had client with audio note single end triode system at well over 100k , & krell system at over £50k system & nuforce £30k system
, sounds better from inverter than the mains , as good inverter has THD under 3% with eltek valere or sma inverters
inverter acts as a high quality regen system like rogue audio/nordorst/ps audio , some top dealers like definitive audio on there £250k plus systems
audio note , living voice systems use 100% non grid power as much cleaner than standard mains supply to improve the sound quality

 

[phase1]

Thanks LightGEN for your insight.My Solid State Amplifier is by no means"high end", but has a continuous output power of 90 Watts per channel, THD 0.01%,,Intermodulation distortion 0.0007%,Residual Hum and Noise 60 into 8 ohms.Looking at the schematic,it has a bridge rectifier,followed by regulators for the various supply rails.There is no sign of the traditional L/C or R/C smoothing as such, presumably this function is carried out by the Regulators? I wonder how these will cope, long term with a Modified Sine Wave?
Thanks also to daytona600.Your experiences are very valid. However, I'm still concerned about the long term effects on equipment designed to work on sinusoidal waveforms when used with Modified Sine Waves.If you Google "windsun.com", and then click on "inverter selection",there is a very interesting article on how various devices respond to Modified Sine Wave power. Once again, thanks to all who have taken the trouble to respond.Regards,Ron.

 

[phase1]

I have just had an email from Mitsubishi telling me that their Gradationally Controlled inverters are not available in the UK, which I feel is rather sad.

 

[daytona600]

i would never use a modified sine inverter , above are all pure sine wave inverters , very similair to high end mains conditioners like isotek & regen units to provide hi quality power to your hifi
and power your house and FITs as a bonus or good off grid inverters sma/studer in event of a power failure

 

[phase1]

Sorry, Daytona600,I don't follow you when you say "all the above are pure sine wave inverters"..The only inverters I can find named on this thread are the ones I mentioned in my opening question. They were SMA, Fronius, and DIEHL,all of which are NOT pure sine wave inverters.I've now contacted the UK Mitsubihi site again to ask if they plan to import the Gradationally Controlled PV-PNS06ATL-IT series into Britain, but have heard nothing from them yet.They would certainly seem to have a much better waveform than the three Modified Sine Wave Inverters mentioned. Regards,Ron.

 

[phase1]

I have now had a further email ,this time from the UK Mitsubishi web site in which it says that their japanese-made inverters "are not currently compatible with UK legislation,so for the forseeable future we will not be selling them in the UK".