|This article is of interest to the following WikiProjects:|
- 1 Diagrams
- 2 The general case
- 3 Good short article
- 4 PDM/digital power inverters
- 5 Ambiguity
- 6 Disambiguation
- 7 What??
- 8 Quality of an inverter
- 9 Three Phase Inverters
- 10 True sine
- 11 modified sine
- 12 Request for ENF Link
- 13 re. Electric Vehicle Drives
- 14 Waveshape marketing
- 15 Requested move
- 16 https://www.littleboxchallenge.com from Google
This page would really benefit from some diagrams. Alaric 14:55 May 8, 2003 (UTC)
- I'd like to see a better diagram than the tube oscillator - which isn't even correct, since the plate voltage supply is backward! --Wtshymanski 18:43, 14 March 2006 (UTC)
The general case
I think this should say that a transformer is ran at a set frequency, but also, a 50 Hz transformer will operate on 60 Hz. Any transformer will operate on higher frequencies with losses no higher than the design frequency, but not vice-versa, until the frequency gets high enough that thinner laminations, or a different core material is required. You can reference the Wikibook article on transformer design here.
Good short article
I think this is one of the better articles explaining electronics on Wikipedia. --Grouse 12:14, 19 Jul 2004 (UTC)
I agree. Explains what was needed. However I think external links should point to sites that contain more info about the topic. Commercial sites should be tagged as such. Does anyone else think the same? I am new here, hence I'm hesitant to change the main page --Padme 21:44, 17 Aug 2005
From the first paragraph of the text, it would seem to me that the opposite would be true for computers. Most PSUs take in alternating current from the wall and convert it to direct.
- You really need to understand switched mode power supplies to understand this. Perhaps the link should be more closely coupled to the psu references, rather than just mentioned at the end of the paragraph. StealthFox 18:48, 13 December 2005 (UTC)
PDM/digital power inverters
- There are many manufacturers of Variable Frequency Drive inverters. They have generally adopted the latest electronic components and design techniques as soon as they have been able to do so. Today, most of these products use embedded microprocessors to control IGBT transistors. Most products use some form of PWM strategy to provide a simulated sine wave output with controlled voltage and frequency.
- I am not familiar with PDM, but it appears to me that the zeros and ones all have the same fixed width and the modulation consists of controlling the number and position of ones vs. zeros. What happens if there are two ones in succession? Does that become a pulse that is twice as wide? I think that PWM power inverters operate like PDM with a lot of instances of two or more ones in succession joined to form wider pulses. Because of the switching losses in the power switching devices, the switching frequency is usually limited to 3 to 9 kHz but the widths and positions of the pulses are adjusted in very small increments. Manufacturers usually publish a product's switching frequency but don't often provide details about the specific scheme that they use for setting the widths and positions of the modulation pulses.
- I hope that helps to answer your question. -- C J Cowie 15:36, 14 March 2006 (UTC)
"Modified-sine inverters may cause some loads, such as motors, to operate less efficiently."
The above sentence is in the article. I can't understand if it means that modified-sine inverters are worse (cause some loads to be less efficient) than a no inverter or than a simple inverter. In other words, the waveform generated by a modified-sine inverter is being compared to what? To a true , perfect sinewave or to the waveform of a simple inverter (one with only two possible voltages)? Ambiguous.
Since I don't know the answer, I can't correct by myself.
- Just saw your unsigned comment. (I have no idea when you wrote it.) Anyway, reading the above quote ("Modified-sine inverters may cause some loads, such as motors, to operate less efficiently."), I would answer your question thusly:
- A modifed sine wave inverter may cause certain types of loads, such as motors, to operate less efficiently than when powered by [alternating current in the form of] a pure sine wave, whether that sine wave be from a "pure sine wave" inverter or regular AC power from the wall outlet. In other words, Pure Sine Wave = best; Modifed Sine Wave = less so. (Square Wave = worst of all.) How much of a difference it actually makes in ordinary practice, I don't know. I regularly use a Modifed Sine Wave inverter to power my microwave oven, and although it causes the oven to "buzz" a little, and seems to heat the food somewhat more slowly (than when powered from the regular wall outlet), it seems to work okay. Hope that helps. Captain Quirk (talk) 18:56, 15 February 2009 (UTC)
Modified Sine Wave here would refer to 3 level types, the ones most common available. The problem is that operating shaded pole and other "synchronous" motors on a Modified Sine Wave source can cause those motors to operate erratically or make a loud buzzing sound, due to the harmonics. For most motors it may be fine and just produce a bit of extra heating, but shaded poles are very frequency sensitive. Mostly clocks, record players, etc. — Preceding unsigned comment added by 184.108.40.206 (talk) 02:15, 3 April 2014 (UTC)
"An inverger is an inverter and a charger in a single unit." What is in inverGer? I assume that is a typo, but if it were corrected then the sentence read "An inverter is an inverter...". Anyone know what point was trying to be made here? — Zero10one 10:22, 8 November 2007 (UTC)
"Simple inverters generate harmonics which affect the quality of power obtained using them. But PWM inverters eliminate this by means of a sine wave cancellation using the properties of Fourier Series." — Omegatron 16:04, 28 October 2006 (UTC)
- Hmmm this is indeed a strange explanation... What about something like "Simple inverters generate square waveforms which are not suited to some application (especially transformers and motors), because of their high harmonic content. In this case, PWM inverters can be preferable" ? CyrilB 16:40, 28 October 2006 (UTC)
- Certainly better. I'm just trying to figure out what the original author was trying to say. PWM inverters generate a more smooth sinusoidal waveform (if built well), while simple switching ones generate a filtered square wave, but what does this have to do with sine wave cancellation or the Fourier series? — Omegatron 18:20, 28 October 2006 (UTC)
- The only thing that the Fourier series has to do with this is that the concept of harmonic distortion, based of Fourier analysis, is used to quantify the quality of inverter output waveforms. "Harmonic cancellation" may be a useful way of describing the effect of PWM techniques in improving the waveform, but it doesn't make much sense as presented. -- C J Cowie 20:45, 28 October 2006 (UTC)
"What??" is a good title for this section. I can't figure out what the first part has to do with the rest, nor what these comments are referencing in the article. - KitchM (talk) 18:20, 12 November 2009 (UTC)
Some of the comments here are correct but, to clarify, both PWM and PDM (Pulse Decimation Modulation) rely on producing a pure 180V square wave (the same voltage used by simple square wave and modified square wave inverters) with harmonics at 60 Hz that can be filtered with a simple and low cost PI filter and the quality of that filter leaves a very low distortion sine wave at 60 Hz and 120 VAC. PDM, by the way, is what a "Digital Amp" uses like the ones from TI's Pure Path Digital Audio Amplifier line of ICs.Joseph Perkins (talk) 13:32, 5 February 2014 (UTC)
Quality of an inverter
The use of the term pulse may need some clarification in thie paragraph:
- The quality of an inverter is described by its pulse-rating: a 3-pulse is a very simple arrangement, utilising only 3 transistors, whereas a more complex 12-pulse system will give an almost exact sine wave. In remote areas where a utility generated power is subject to significant external, distorting influences such as inductive loads or semiconductor-rectifier loads, a 12-pulse inverter may even offer a better, "cleaner" output than the utility-supplied power grid, and are thus often used in these areas. Inverters with greater pulse ratings do exist.
I believe that the term pulse here refers to the number of steps in the inverter waveform. The six-step waveform is described in the article. A square wave would be a two-step waveform. There are also multiples of the six-step waveform such as 12-step, 18-step and 24-step.
The term pulse is often used to describe AC to DC converters. I can't find any references that use the term pulse as it has been used here.
If no one objects, I think I will change this paragraph to describe 12-step, 18-step and 24-step inverters and eliminate 3-pulse etc.C J Cowie 21:31, 8 November 2006 (UTC)
- The article Pacific Intertie describes 6-pulse converters. I've long intended to look up what that means and verify correct usage. Are you proposing to eliminate mention of 6 pulse? — EncMstr 00:09, 9 November 2006 (UTC)
- The 6-pulse and 12-pulse converters described in the Pacific Intertie article are phase-controlled AC to DC converters and also the same circuits operated as line commutated AC to DC inverters. This article does not cover line commutated inverters. There are also load commutated inverters that are not covered here. These are all controlled rectifier circuits. I think that it might be best to cover the various types of controlled rectifier circuits all in another article and eliminate the terms 6-pulse and 12-pulse from this article.--C J Cowie 00:47, 9 November 2006 (UTC)
Three Phase Inverters
The three phase inverter section is dominated by line commutated inverter information. PWM three phase inverters need to be broken out into a separate section.
So how does a true sine or pure sine inverter work? --Pascal666 01:12, 1 November 2007 (UTC)
- There is no such thing as a true or pure sine inverter, every inverter has some harmonic distortion. Inverters labeled as True or Pure sine are really making a relative comparison to other inverters on the market. The small consumer and domestic inverters generally are either modified sine which is the square wave with gaps waveform mentioned(THD = 30%), or variations on PWM output (which can usually get THD of about 2% - for comparison, an audio amplifier with 2% THD would be considered low-fi).
- For common PWM inverter designs the power is boosted via a DC-DC converter then fed via an H-bridge to the output. The control of the H-bridge is the dominant factor in the final output, as power transistor tech improves the switching speed increases and the THD decreases. For comparison, coolamp produce a 90% efficient switched amplifier with THD < 0.01% (you can consider the DC-AC portion of an inverter as a specialised amplifier). --Jaded-view 00:34, 3 December 2007 (UTC)
- All DC/AC inverters use a transformer based forward converter to convert some DC voltage to a much higher DC voltage (typically 12VDC to 140-180VDC). All a forward converter is doing is operating as an oscillator with a push/pull driver (can be any kind of switch, but symmetry of drive is crucial) feeding the transformer at some arbitrarily high frequency. The higher, the smaller the transformer for a given power rating. The output of the transformer is rectified to about 140 to 180 VDC and fed to the output stage. This is then one of many forms: A simple 60Hz H bridge where opposite transistors are off and on at the same time produces a 140V Peak to Peak square wave (RMS voltage 120VAC). A controlled 60Hz H bridge that makes one intermediate step of all drivers off produces a "Modified Square Wave" output. Adding a second voltage tap and expanding the H bridge into a double H bridge gives a better "Modified Sine" wave. Running the H bridge at some arbitrarily high frequency as in PWM or PDM modulation and adding a simple PI filter to remove those high frequencies leaves a fairly clean 60Hz sine wave. The more sections in the PI filter and the higher the modulation rate, the cleaner the sine wave.Joseph Perkins (talk) 13:49, 5 February 2014 (UTC)
The term modified sine redirects here. Our WP:REDIRECT#PLA guideline suggests that we should have the words "modified sine" in bold in the first few paragraphs of this article. Currently, the word "modified" currently does not appear anywhere in this article (except in the External links section). That external link illustrates a "modified sine" with a picture that looks like a square wave to me. I thought "modified sine" was different from a square wave?
Was important information accidentally lost in that ancient edit? Which one of the waveforms currently described in this article is the "modified sine"? --220.127.116.11 (talk) 00:21, 28 August 2009 (UTC)
- My understanding was that a "modified sinewave" is a waveform that is on positive for a quarter cycle, then zero for a quarter cycle, then negative for a quarter cycle then zero for a quarter cycle. This waveform has the important characteristic that it's peak to RMS ratio is the same as a sinewave.
- The peak to RMS ratio is important because resistive loads rely on the RMS voltage of their supply while rectifier based loads rely on the peak value. A square wave inverter that is set up to provide the correct voltage for rectifier based loads will provide an overvoltage to restive loads and a square wave inverter that is set up to provide the correct voltage for resisitive loads will provide an undervoltage to rectifier based loads.
- The current article seems to completely ignore the peak to rms ratio and treats "total harmonic distortion" as if it is the only important parameter of an inverters output. Sadly I don't have enough experiance to fix this myself. Plugwash (talk) 02:46, 16 August 2011 (UTC)
- You are correct. A better way of creating the modified square wave (frequently incorrectly called a 'modified sine wave' - there is nothing sinusoidal about it, probably the product of marketing folk), is to add two regular square waves together, one of which is phase shifted by 90 degres relative to the other. By the way: the illustration in the article does not correctly depict such a wave as the two square waves appear to be phase shifted by much less than 90 degrees (somewhere around 33ish degrees). 18.104.22.168 (talk) 14:28, 18 February 2014 (UTC)
Request for ENF Link
We have been researching solar inverter companies for over three years, and have built up a list of 170 solar inverter manufacturers here: ENF PV Inverter Industry Directory
It is not only a list of all the inverter manufacturers around the world - we have also researched the power range they are producing, and whether they are on-grid or off-grid inverters.
I notice a link on the page already to an information page on solar inverters, and I think that the page I am suggesting is just as relevant and I would highly appreciate an appropriate link being added.
- Looks like a well done and highly useful link. I think it makes a fine addition to the article. —EncMstr (talk) 05:46, 3 March 2009 (UTC)
re. Electric Vehicle Drives
There is a little confusion in this section where it states, "In vehicles with regenerative braking, the inverter also takes power from the motor (now acting as a generator) and stores it in the batteries.".
This should probably state two different possibilities. One is that the drive motors are DC and another where they are AC.
If they are AC, then they would need a rectifier when they became alternators and began generating AC current. If they are DC, then they would need neither an inverter or a rectifier (but perhaps a transformer) when they became generators and began generating DC current for the batteries. - KitchM (talk) 19:06, 12 November 2009 (UTC)
I do not believe that a AC motor generates AC at a free spin. I have set-up VFD's on boiler blower motors and have often ran into one certain problem. See a VFD "using rectifiers" monitors back voltage to determine or gage its speed, if you will, on a programmed scale. This back feed is called the DC bus voltage back feed of the AC motor at a free spin. As the control demands less from the motor and ramps down producing a decrease in frequency. A ramp down time must be programmed as a blackout period until the motor is delivering a DC bus back feed that correlates to the frequency output of the drive.22.214.171.124 (talk) 14:22, 7 May 2010 (UTC)
Electric motors in hybrids and in "all electric" vehicles are more related to stepper motors. This is evidenced by the three conductors fed to each motor. This makes the sense of AC or DC a rare duck as it is both and neither.Joseph Perkins (talk) 13:58, 5 February 2014 (UTC)
It would be interesting to find a reference that compares the much-maligned sqaure-wave inverter with the so-called "pure sine wave" types for computer UPS purposes. Since the first thing that the AC power hits in the power supply is a rectifier, say good-by to the "sine" wave early on; it seems to me that a square wave might be a much better waveform to feed a rectifier than a sine, since the peak and RMS values are closer. There's nothing in a modern personal computer that cares about the wave shape. You could probably run a computer power supply on white noise if you could get enough of it...--Wtshymanski (talk) 16:53, 3 March 2012 (UTC)
recently had a pair of books out of the libary that covered invertors and they may be of use for references here . "Power electronics" Lander, Cyril W, ISBN: 0070841624, 9780070841628 . And "Principles of Electric Machines and Power Electronics", Sen, P. C. ISBN: 0471850845, 9780471850847 Contrary to this article both recon square wave invertors can be fine for powering devices which have significant inductance eg big motors, as the inductance smooths out the current waveform -The powered device needs slightly derated to account for the difference in I-V curves.Yes that can play havock with the power factor (Affects the supply, not the powered device, and can be mitigated with by power factor correction) Not sure how it would effect low inductance electronics but probably worth a read. 126.96.36.199 (talk) 14:37, 14 March 2012 (UTC)
The problem with feeding anything but a pure sine wave to a UPS is it can, and does, cause the UPS to see the incoming power as being "bad" and it will switch back and forth between battery and AC power and not survive this very long. That's why cheap inverters and generators with THD higher than 5% must NOT be used with a UPS.Joseph Perkins (talk) 13:53, 5 February 2014 (UTC)