Toridal Mains Transformer

I could talk at length about IEC1000-3-2 and the fallout from it !

Especially the range of products covered by Class D.

Oh... not to mention the implementation date !

If you're not up to date on compliance issues you won't even have the remotsest clue what I'm on about. Actually - if you're upto date you probablt won't know either ! It's the history of this standard.

That's half the trouble actually. No-one knows what the IEC might drop on us next !

Graham

p.s. AAArrrrggggjhhh !

Some Pommy Idiot:

** It is very definitely power factor:.

Power Factor = power in watts / VA

** So will most small ones.

The only obvious difference is the absence of magnetising current with a SMPS.

......... Phil

** How bizarre - another who had never checked the AS current waveform of a linear supply.

A 500VA PSU delivering 400 watts DC is not modest power for certain classes of device.

** Toroidals have very low I mag figures and very low leakage inductance.

So PSUs using them have AC current waveforms identical to ( non PFC ) SMPS.

........... Phil

I read in sci.electronics.design that Ross Herbert wrote (in ) about 'Toridal Mains Transformer', on Fri, 9 Sep 2005:

Maybe not higher than 0.5. The higher the efficiency of the power supply, the shorter the conduction angle at full load and thus the lower the distortion power factor.

Maybe not at zero load, but quite often at low load.

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that Ross Herbert wrote (in ) about 'Toridal Mains Transformer', on Fri, 9 Sep 2005:

Some>>Btw, your statement that " The only thing between the PFC and the smps proper

is

No, please read what you originally wrote. What comes between the PFC and the SMPS? It depends on what you consider part of the SMPS. But EITHER you should not have included the EMI filter OR you should not have included the rectifier and capacitor.

Your response shows that your original statement is mixed-up. I'm sure you know that the sequence is:

Input connector, fuse, EMI filter, switch (preferably in that order)(*), PFC, rectifier, filter capacitor, rest of SMPS, load(s).

(*) Because the most likely places to get L-N short-circuits are the filter and the switch, so precede them with the fuse.

More RF stuff, less low-frequency stuff (harmonics). Take your choice, if you aren't selling to Europe.

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that Pooh Bear wrote (in ) about 'Toridal Mains Transformer', on Fri, 9 Sep 2005:

I do. (;-)

-- Regards, John Woodgate, OOO - Own Opinions Only. If everything has been designed, a god designed evolution by natural selection.

Also see

I read in sci.electronics.design that Ross Herbert wrote (in ) about 'Toridal Mains Transformer', on Fri, 9 Sep 2005:

You can calculate it for slightly simplified cases, or simulate it. I've never bothered to tabulate the PFs for different conduction angles because the requirements are specified in terms of harmonic currents or current ratios, not PF.

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

** Irrelevant.

The general definition of Power Factor is and has always been :

** Power Factor = power in watts / VA **

** Irrelevant to the correct usage of the term: Power Factor. How strange indeed that the modern, electronic device that removes the distorted current waveform is called, of all things, a *** Power Factor Corrector !!! *** !!!!!!

** Fraid it is very much so.

** So now you say the actual current waveform is irrelevant to the harmonics spectrum ?? ** Not at all, I do not troll.

But just as bloody usual - you are.

.......... Phil

I read in sci.electronics.design that Richard Crowley wrote (in ) about 'Toridal Mains Transformer', on Thu, 8 Sep 2005:

Yes, because for every one theatre there are 10 000 small power supplies at say 100 W average, = 100 thousand watts.

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that Pooh Bear wrote (in ) about 'Toridal Mains Transformer', on Fri, 9 Sep 2005:

You get into the realm of positive, negative and zero-sequence currents, which electronic engineers are not allowed to know about. (;-)

Hot neutral is one effect, the major cause of concern in USA, I'm told, but there is another one:

- the limited current available from normal 120 V outlets considerably restricts the actual power available if the load has a poor power factor (of either sort).

But in Europe, there are two other concerns:

- effects of harmonic currents on reactive components in the supply system and at load sites (e.g. PFC capacitors drawing very large currents at high harmonic frequencies) and inductors in the supply system (large harmonic voltages generated across them);

- I^2R losses due to harmonic currents. These cost the electricity suppliers (and hence every consumer) and ***contribute to global warming** both directly and through extra fuel consumption. Shock, horror!

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

"Ross Herbert" "Phil Allison"

** Bunk.

Large and small linear supplies typically have PFs of around 0.45 to 0.65 even at rated load - the lower numbers will be for those using toroidals and C-cores.

** Cut the talking down crap.

** Not relevant to the OP's post or mine.

** Of course - but as they provide no isolation the output cannot be ground referenced.

By using a 500VA, 1:1 isolation tranny on the input, the OP is solving that issue for his app.

Has the penny dropped yet ?

........... Phil

"Richard Crowley"

** A single desk PC draws maybe only 1 amp rms or so.

But what happens when you have a office tower block with 5,000 of them ??

........... Phil

"Ross Herbert"

** Dear Ross,

there is *actually* nothing between the PFC stage and the SMPS proper.

...... regards, Phil

Some Demented Pommy

** The neutral conductor disaster ( as it is popularly known) is solved by simply fitting an oversize neutral, or independent neutrals for each phase - making 6 conductors plus earth. Doing this in each large office building would seem far easier than making *every* piece of electronics on earth have PFC PSUs.

However, even then the major problem of poor PF remains since the installed cabling in a premises can only handle a certain current level safely and if the PF is made close to unity then far more gear can be run on the existing cabling, transformers and AC supply systems.

......... Phil

"Ross Herbert"

** Quote:

" The only thing between the PFC and the smps proper is the EMI/RFI filter and bridge rectifier and input filter capacitor. "

BTW How long is Ross's nose ??

........... Phil

"Ross Herbert" "Phil Allison"

** Where is the source for your comment?

Does it take a mirror for you to see it?

You can check linear PSU maker's data sheet for the PF figures. Or test some yourself.

I must have tested thousands by now with my " RMS Current Monitor", published in Electronics Australia in May 1997.

** *Actually* - I meant you to cut the talking down crap - *actually*. ** Yawn.

** He did - *actually*.

He *actually * said he wanted an isolated 300 volt DC supply -

*actually *.

** Well, he *actually * said his need was for a PFC & isolated DC supply - *actually*.

It is *actually* mentioned in the very first line of his post.

** Well, *actually * Ross, I am not guessing.

I *actually * read the OP's post very carefully.

" I am currently working on a system where I need about 1.3A at 300V DC, isolated and Power Factor Corrected."

" I am currently working on a system where I need about 1.3A at 300V DC, isolated and Power Factor Corrected."

" I am currently working on a system where I need about 1.3A at 300V DC, isolated and Power Factor Corrected."

** That would be because I *actually * answered his simple query long ago.

......... Phil

In article , John Woodgate wrote: [...]

Before someone else does, I'll jump in with one exception to the "Any linear supply". The really huge supplies that are powered from 3 phase power and run an inductive filter off the bridge have a wider conduction angle. In general, if two people can lift it, it will fall under the "Any" above.

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kensmith@rahul.net   forging knowledge

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kensmith@rahul.net   forging knowledge

I read in sci.electronics.design that Ken Smith wrote (in ) about 'Toridal Mains Transformer', on Fri, 9 Sep 2005:

They draw square waves of current, and the European requirements for harmonic emissions at those sorts of power level are quite tight (IEC/EN

61000-3-12). They have been set so that they can be met with a reasonable amount of passive mitigation (series inductors), except that one of our Finnish colleagues says they can't. At that point, my brain begins to hurt. (;-)

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk