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Why not always use a 3 phase rectifier instead of Boost PFC?

zenerbjt

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If you are a company with a 3-phase supply to your premises...then why ever would you want to design a Boost PFC?.....After all, the 3 phase 6 pulse rectifier is PFC'd to a good degree...and even at 100W say, its cheaper than a Boost PFC.
 

wwfeldman

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I don't think companies have a 3 phase supply for 100 Watts.

for "PFC'd to a good degree ", what is a good degree?

PF is not the only issue.
harmonic content is an issue for the power company also
 

KlausST

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Hi,

The phase current waveform is totally different on PFC and 3 phase rectified.
And the waveform determines overtones and this determines quality.

When one talks about PFC cost, then one needs to talk about 3 phase installation and connector cost, too.
For 100W.

Klaus
 

zenerbjt

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Thanks, but sorry, i didnt mean that they should get 3 phase installed just for the sake of doing a 100W PFC supply....what i meant was...if the company "already" has a 3 ph supply, then why not use it (with a simple 3 phase rectifier) for getting eg 100W power factor corrected supplies?

I realise a 3ph rect supply isnt as good with THD as a proper boost pfc...but its a lot cheaper...and still passes regulations.
___---___---___---___---__---___--____--__

please may i ask another PFC question..?

The following states that its possible to get 98.6% efficiency with a CCM Boost PFC that doesn’t use SiC diodes…

https://e2e.ti.com/blogs_/b/industr...nd-cost-competitive-choke-in-pfc-applications

Surely this is wrong?
 

FvM

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We use three phase DIN rail supplies in control cabinets, not 100 W, but e.g. 240 W. It's reasonable if the system is already three phase supplied. Otherwise single phase switcher (with PFC according to state of the art) is the cheaper solution. Having three phase outlets somewhere in the company isn't the point.
 

zenerbjt

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Having three phase outlets somewhere in the company isn't the point.
Thanks, but i dont understand.....if a company has a three phase supply, and then finds it needs a 100W PFC'd supply, then surely they just use the three phase supply and a 3 ph rectifier? (ie, rather than a PFC'd Boost)
 

FvM

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I also don't understand. Do you mean that costs for 3 phase wall outlets, connectors and cables are irrelevant?
 

zenerbjt

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Thanks that is a good point, and i apologise because i should have specified..... i am taking it that those installation details are all taken care of.
And the company has choice between one phase into a Boost PFC, and three pjhase into a 6 pulse rectifier.
 

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