inverter question - Page 1
Forum section: electronics / general

author: vivi-d
author_rank: Regular Contributor
timestamp: July 26, 2021, 07:21:41 pm
content: Hello Everyone!Is there a big difference between pure sine wave inverters and (modified sine wave, square wave) inverters?If the inverter is powering a device with a full wave bridge rectifier, is there really any difference between the two?Thanks!

author: bob91343
author_rank: Super Contributor
timestamp: July 26, 2021, 11:19:51 pm
content: Yes there is a difference. The waveform will vary depending on how well designed the inverter is, and how much it costs. The utility of various waveforms will depend on the application.In other words, there is no simple answer. Some loads don't much care about waveform; others do. And the noise will vary.

author: james_s
author_rank: Super Contributor
timestamp: July 27, 2021, 12:02:46 am
content: There is a very big difference in the output, whether that greatly affects the device you're trying to power is impossible to say without knowing more about the device in question. Anything with an iron transformer or motor will tend to buzz noticeably when connected to a "modified sine" which is just a square wave with dead time. Some devices like phase control dimmers won't work at all, and I've seen other devices burn up but most stuff like computers and modern TVs and other stuff with switching power supplies doesn't really care. If you need it for a specific application then modified sine may be just fine, but for more general purpose use pure sine is always preferable.

author: fourtytwo42
author_rank: Super Contributor
timestamp: July 27, 2021, 07:54:15 am
content: Quote from: vivi-d on July 26, 2021, 07:21:41 pmThere are not many devices left around with such a simple input as for most products PFC has been mandated for many years and that is certainly waveform sensitive. I think modified sinewave has largely been consigned to the dustbin of history except for those offshore copycat manufacturers who know no better and the unfortunate unaware consumers who still buy them (presumably because they are dirt cheap).

author: Just_another_Dave
author_rank: Regular Contributor
timestamp: July 27, 2021, 09:55:32 am
content: The main difference between them is the harmonic content of the output voltage. Many loads, as well as the mains, require harmonics above the fundamental one to have an amplitude below certain levels. This can be achieved by adding a filter between the converter and the load, which can add a significant volume, cost and weight to the product. Therefore, different modulations can be used to reduce the harmonic content and, as a consequence, the required filter (modified sine wave, PWM, symmetric PWM, etc).A pure sine wave inverter would be the best solution in terms of EMC as it ideally does not produce high frequency harmonics. However, if it is implemented with bipolar transistors, the efficiency of the converter will probably be quite low, which is not great in case it will be used for supplying high amounts of energy. On the other hand, resonant converters have really high efficiencies at their nominal operating point, but they can be difficult to design.Consequently, as previous comments have stated, the topology used in each product needs to be chosen according to the requirements of the load and the expected cost of the final product

author: james_s
author_rank: Super Contributor
timestamp: July 28, 2021, 12:46:21 am
content: Quote from: fourtytwo42 on July 27, 2021, 07:54:15 amModified sinewave still accounts for the vast majority of inverters on the market, at least in the sub-2kW size range although pure sine inverters are slowly getting cheaper and more common. The vast majority of consumer/small business grade UPSs are modified sine too when running in battery mode.

author: fourtytwo42
author_rank: Super Contributor
timestamp: July 28, 2021, 02:09:18 am
content: Quote from: james_s on July 28, 2021, 12:46:21 amGuess I was thinking from the point of view of a PFC controller given some horrible waveform to work withGuess I was making a poor attempt to explain to the OP that not everything with a bridge rectifier at the input can be classed as simple and waveform immune

author: PKTKS
author_rank: Super Contributor
timestamp: August 02, 2021, 10:51:28 am
content: Quote from: fourtytwo42 on July 27, 2021, 07:54:15 amWell.. I grew up with a "class" of electronics that today seems to be called as "vintage"...Several devices from the top notch builders boasted the "HI-FI" property which certainly would put them above the underclass cheapos...A HI-FI device usually has a thing called "linearity" and devices with absolute noise ratings order of magnitude better than cheapos..Careful construction, shielding and LINEAR (Yes.. linear PSUs) where the linearity of components were top priority.. not price or size...I was certainly spoiled with SANSUI.. AKAI.. Marantz.. and dozen others..TODAY.. well today some hairy heads worried because their parents consumed too much and the wasteland landfill of resources are stinky more than ever...well today these HAIRY HEADS "MANDATE" .. the whole world to do things like using PFC SMPS... and ditching all linear things because they say digital is somewhat safer better whatever..Truth is... there is no more noise crap than a PFC SMPS and a digitally made signal from a patented chip algo. sold 10x the price..Crap is crap. Audio and video today are garbage non linear stuff.sold as better for people without a clue about Hi-Fi.I really miss the old HI-FI all Linear stuff..I am spoiled... too much AC/DC TYA and JH on the woofers..So TODAY it seems that SINE INVERTERS although still required by these PFC noise generators are becoming a very expensive luxury.. just because the audio garbage is already all digital and there is nothing linear left...Still the SINE INVERTER with linear response should be useful..And I really doubt that Angus will ditch his Marshall head tubes...Paul

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 06, 2021, 12:25:43 am
content: Quote from: PKTKS on August 02, 2021, 10:51:28 amHasn't the gap between the state of the art digital video and state of the art film narrowed considerably if not mostly eliminated? I suppose there are specialty applications were film still isn't beat, but otherwise digital offers comparable quality without the many disadvantages of film.

author: PKTKS
author_rank: Super Contributor
timestamp: August 06, 2021, 04:08:32 pm
content: Quote from: NiHaoMike on August 06, 2021, 12:25:43 amDon't see that...Appart the fact of digital video has a better "resolution" (more pixels)It does require insane hardware to process data..Without dedicated decoders/encoders... and a considerable PSU...Well digital video is crap.No surprises seeing these "integrated AV receivers" in landfillsYou need patented decoders dedicated hardware. high power..Audio is tracking that but these D-class amps seems the utmost garbage*MAY* be the Hi-Fi days are gone..nevertheless.. these "crappy days" should be over as well.They are selling digital crapPaul

author: PKTKS
author_rank: Super Contributor
timestamp: August 06, 2021, 04:20:57 pm
content: ALAS...WTF is has todo with INVERTERS?PFC SMPS are noise generators.If used with non true sine inverters the results are insanely bad..(tried myself on the bench..)Thus PFC -SMPS generation gizmos do require TRUE SINE INVERTERS..And this will not help the noise ..only avoid 100x worse results.Paul

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 07, 2021, 04:25:27 am
content: My experience is that most PFC stages run just fine on DC or square wave.Quote from: PKTKS on August 06, 2021, 04:08:32 pmActually, digital matching the resolution of film is a relatively recent breakthrough. Digital overtaking film was due to other factors like convenience, ease of editing, the storage medium is reusable many times, being able to review clips on site and reshoot if something's not right.QuoteHave you even processed any film, photographic or video? Especially for color, the chemistry is really complex and took lots of tweaking to get right.There are open video codecs:https://en.wikipedia.org/wiki/AV1

author: Siwastaja
author_rank: Super Contributor
timestamp: August 07, 2021, 09:53:45 am
content: Processing color film is actually quite simple to get right, but that's because 95% of the magic is hidden in the film, and the remaining 5% magic in the pre-packaged chemistry, which when talking about color, is nearly impossible to mix or synthesize from the usual lab reagents due to the existence of special molecules like Kodak's proprietary CD-4 the oxidation products of which react with the color couplers in the film forming the dyes.There is almost no limit on the "resolution of film" because you can always easily go to a larger size with quite manageable price increase. I don't know currently but up until recently 8" x 10" sheet film was easily available, this is easily equivalent to some 1000 megapixels. Such large semiconductor sensor would be truly expensive! I had a modern film camera which used the convenient 60mm wide roll film to shoot 70x58mm frames, I made some optical enlargements to 50x40 cm size and you can look at them with a magnifying glass with absolutely no grain visible and much much sharper definition than a 300dpi digital print, outperforming the 20MP digital SLRs available back then by an order of magnitude. Obviously, there is no point in doing this but hobbies are hobbies...

author: Microdoser
author_rank: Frequent Contributor
timestamp: August 07, 2021, 10:26:06 am
content: Film runs around 100 Megapixels per frame. Once digital exceeds this, then it will be possible to start saying digital is better than film. Of course, with cameras such as a Red, which has 18 stops of HD, there are areas where digital cameras are better than film, but to my mind digital will need to at least match the resolution of film before it can be called better.Regarding inverter types:

author: PKTKS
author_rank: Super Contributor
timestamp: August 07, 2021, 02:56:35 pm
content: Quote from: Microdoser on August 07, 2021, 10:26:06 amYep still the films are better..I have seen some old high quality stuff "converted" to digital in 21:9 or more wide screen with an incredible high quality.. even old stuff exploited by TV broadcasters in 4:3 when converted from TeleCine can reach better quality than if filmed today..One issue DIGITAL is for sure unbeatable: NON LINEAR DIGITAL EDITIONbut you still need to put stuff back into some "format"On the bench a simple test can be done:- RUN YOUR INSTRUMENTS AND COMPUTERS FROM UPS (non true sine)- REMOVE POWER. let the UPS kick in.- Follow the amount of interference introduced in *ALL* your bench...all PFC SMPS will start whining like hellPaul

author: james_s
author_rank: Super Contributor
timestamp: August 07, 2021, 09:51:15 pm
content: I don't think you can easily make a 1:1 comparison on film vs digital resolution. A digital image is a fixed grid of pixels, each discrete pixel will have a specific luminance value and there is nothing in between. Film is completely analog, the grain is not laid out in a grid, you can approximate the equivalent resolution of film but it isn't going to look the same for the same resolution.

author: DannyG
author_rank: Newbie
timestamp: August 12, 2021, 03:06:44 pm
content: If the output of the inverter is the same rated amplitude and frequency as the input specs for the rectifier, then you should be fine.The diodes should turn on and off the same time regardless if its a square or sine wave. If its a square wave you should get more of a pure DC output on the rectifier.Now if there's a bunch of noise on the inverter, it will show up throughout the circuit.I'm aware my response is different from the rest on this post so I'm sure I'm missing something that everyone else noticed.

author: james_s
author_rank: Super Contributor
timestamp: August 12, 2021, 08:00:32 pm
content: It isn't just a square wave though, it's a square wave with dead time. The ripple current is definitely going to be higher.

author: f4eru
author_rank: Super Contributor
timestamp: August 13, 2021, 08:38:11 pm
content: Quote from: DannyG on August 12, 2021, 03:06:44 pmHmm. Nope.

author: TimFox
author_rank: Super Contributor
timestamp: August 13, 2021, 08:47:58 pm
content: Quote from: james_s on August 07, 2021, 09:51:15 pmThe random layout of grains, which have a distribution of sizes, is an important difference between film and digital (with its periodic matrix of discrete pixels).Digital has killed 35 mm in the market due to comparable performance with much more convenience and lower cost. It can have a technical advantage over film in low-light applications, especially since the very high speed films are now gone.My largest camera uses 8x10 inch sheet film. Depending on optics, etc., it may achieve 100 to 200 lp/mm on a 200 by 250 mm image. Sheet film (up to at least 8x10) is still available in b/w, E-6, and C-41 processes. Since there is no periodic sampling, aliasing is impossible.