Talk:Inverter (electrical)

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[edit] Diagrams

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)

[edit] 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)

I took out he following sentence: An inverter can have one or two switched-mode power supplies (SMPS).. Maybe it's the other way around? --Apoc2400 07:23, 3 March 2006 (UTC)

[edit] PDM/digital power inverters

Do digital power inverters exist? Do there exit any power inverters, analog or digital, that use pulse density modulation (PDM)?Myrtone (the strict Australian wikipedian)(talk)|contributions|Testpage

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)

[edit] Ambitguity

"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.

[edit] Disambiguation

I don't think this page should get primary-topic disambiguation. The word 'inverter' is used very often to refer to NOT gates. --Smack (talk) 02:03, 14 June 2006 (UTC)

[edit] What??

"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)

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"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)

[edit] 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)

[edit] 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.

Also, voltage source and current source inverters need some coverage. —Preceding unsigned comment added by Wefoij (talk • contribs) 23:10, 2 September 2007 (UTC)

[edit] True sine

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)