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Where are high PF rectifiers used?

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bonzer:
Hello everyone, sorry if I sound stupid with such questions but I studied time ago rectifiers with high power factors that emulate variable load after graetz bridge to reduce current harmonics number. They use buck boost or fly-back converters for that.
Where are they used? Do they already use them in new generation battery chargers for mobile phones? Or in some particular applications? I think such a type of system is efficient but has a higher cost than classical simple graetz rectifiers with ICs like 7805 because there's also a control part and duty cycle generation etc ...

ferdieCX:
I think, that the PC power supplies with 80 Plus certification use this kind of rectifiers.
Also the quality on-line UPS systems are usually of this type

T3sl4co1l:
FYI, we usually call that "active PFC", but rectifiers can also be used passively to give high power factor -- what might be terms "high PF rectifier".

In three-phase systems, we can use transformers to construct any phase angle we like; by interleaving many phases, we get a "6N-pulse" rectifier (N = 1, 2, ...). The normal 3-leg FWB is a 6-pulse rectifier, which has ~0.9 PF.  Using a delta-wye transformer, we get a 30 degree phase shift almost for free, and adding another 3-leg FWB, we get a 12-pulse rectifier with even better PF.  And so on.  These are relevant to very high power (MW+) industrial systems, where simplicity and reliability, and economy of scale to some extent, overcome the size/weight/cost concerns that are more important to smaller equipment.

This isn't applicable to single-phase systems.

Tim

bonzer:
Thanks a lot for your answers!

I'm glad you all mentioned the different categories by power. I also know about 6-phase modulation (space vector approach etc), thanks for mentioning.

T3sl4co1l:
Well, that would be the other side of it -- synthesis; an inverter turning DC into AC, rather than the other way around.

Tim

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