Power factor correction

PFC is a flyback thing. But flybacks suck over 100W, where forward looks better. But forward sucks over wide duty cycle ranges. What do they do, just bigger flybacks? Nothing at all?

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Reply to
Tim Williams
Loading thread data ...

On a sunny day (Tue, 29 Dec 2009 07:17:31 -0600) it happened "Tim Williams" wrote in :

For much higher power 3 phase rectifiers are used. That leaves only a small ripple. I am not sure if you need PFC in such a case.

Reply to
Jan Panteltje

"Tim Williams"

** Come back when you sober up.

Fuckhead.

... Phil

Reply to
Phil Allison

ks

do,

At modestly larger that 100W the flyback booster method still works ok. The bulk of the power is transfered by the booster when its boost ratio is small. To handle the very wide duty cycle dropping the frequency as the mains nears its peak works.

Multiple boosters running out of phase will let you go up to higher power levels and the ripple tends to cancel.

Other designs do use various sorts of forward converters. No matter what you do, you need to have a core somewhere that has a significant energy storage. To make the forward converter method work, the output side inductor has to do the storing. Going up in frequency, keeps the inductor's mechanical size smallish.

Reply to
MooseFET

They use CCM Boost topology for PFC.

See NCP1654 for example.

formatting link

Reply to
Hammy

Coilcraft has the inductor for the Onsemi APFC.

formatting link

Reply to
Hammy

Tim Williams a écrit :

Flybacks work great in PFC but have pulsed input current which isn't so great. The usual PFC is a boost, but you don't get isolation and have to manage inrush current.

I once did a 250W isolated sepic PFC with zero input ripple. Worked great with none of the above pb. I think I've made a couple of posts here. 't was circa 2001-2002.

--
Thanks,
Fred.
Reply to
Fred Bartoli

Maybe, maybe not. You get 60 degree conduction, which isn't quite 90, so maybe it would benefit some. Where cap input filters are used, conduction can still be narrower and peakier.

What I'm most interested in is single phase, since there's a small band between 2kVA-20kVA where single phase is available. My welder runs from a

240V, 50A circuit, for instance. Just imagine how many home machinists have their shops wired with, say, a 240V 100A circuit, and have all their machines running from a rotary phase converter because nobody mades single phase motors over 1-2 HP. Three phase simply isn't an option for residential in the U.S..

So I guess flyback (well, boost) is still the way to go? Just more phases? Three phase I suppose would be a good start for this power level? I don't like the idea of CCM, even at 200kHz those inductors will be bigger than the rest of the circuit after it!

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Reply to
Tim Williams

so

ion

m a

have

e

ses?

n't

the

You can make the current go continuous at the peaks and discontinuous at lower points. It makes the control a bit harder but makes the inductor a lot smaller.

You can also make the frequency rise as you go to the lower voltages. The frequency and inductance can be optimized for near the peak voltage. Since this is where most of the power transfers, the efficiency is dominated by it. You can then raise the frequency as you go to lower voltages to semi-optimize at each voltage point.

Reply to
MooseFET

I was looking at the FAN9611 the other day. BCM is nice because it uses "all" the inductor's capacity. Now, the datasheet says it's useful for

100-1000W, but do you think it'd be good for another decade beyond that? What scares me is the frequency clamp stops at "only" 520-750kHz. I don't think I want to deal with that much dV/dt and dI/dt just yet...

It doesn't look like Fairchild is making more than biphase chips... TI has the UCC28070 which looks fairly equivalent (with constant frequency instead). Offhand, I'm not finding anything with more than two phases.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Reply to
Tim Williams

s

n't

You can never trust the makers "good for from here to there" on controller chips. The limitation is largely the result of how much current the outputs can produce. They assume "reasonable" values for the gate charge per drain current rating of the MOSFET and work out how much current that comes out to.

As new MOSFETs are introduced, the ranges become sort of nonsense.

s

The amount of advantage decreases with increasing number of phases. You can always make N copies of the 2 phase circuit to get N times the power. Making them share isn't going to be too hard to do.

Reply to
MooseFET

For home shop use, a VFD can't be beat. You get variable speed, soft start and dynamic braking. Running a 5 Hp + 3-phase machine motor off one of those "phase converters" will sure dim your lights on every start. An RPC is better, but makes noise and sucks power all the time it is running. Neither gives you braking. if you have a big lathe with no mechanical clutch/brake setup, the long coast time can be an actual safety concern. My 15" Sheldon lathe would coast 20 seconds by itself, but stops in 3/4 second by the VFD.

The typical larger PFC scheme uses a boost converter that is modulated by the voltage waveform, so the current draw matches the instantaneous voltage, scaled by average current demand. This stage precedes the main converter, which would usually be a push-pull design, and you can use the topology and drive scheme of your choice in that converter.

Jon

Reply to
Jon Elson

I've done a 2kW CCM PFC using a boost converter - the inductor was pretty massive (several pounds at least), but then again it was running at 50 kHz. (It was DSP-based, so the control loop couldn't run much faster.)

It was for a 2HP VFD, and there wasn't any size or weight constraint, otherwise I would have figured out how to use a higher frequency with a smaller inductor.

I seem to remember Bi Technologies made some power modules designed for PFC converters in the 2-3kW range, and had some app notes for them.

- Alan

Reply to
Alan W

Unless you're cheap, which most of rec.crafts.metalworking IS. ;-) When you get a lathe for $200 and a case of beer, VFDs don't look so cheap. They're definitely nice though.

As for electrical characteristics, VFDs are a fine example: what do they do for PFC? Nothing? The VFDs installed in the school's power lab are 10 or

15HP, three phase input, and according to the Fluke PQAs, current is spikey as hell, no PFC, big gulps of capacitor charging. Doesn't seem very nice to me, and when you're losing half your VAs in harmonic current, it's just not practical from a single phase supply.

Yeah, but that doesn't work well at let's say 400V and 30A. The inductor is huge, and it's an awful lot of ripple on the capacitors. There's gotta be a better way (multiphase helps).

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Reply to
Tim Williams

looks=20

do,=20

What? Even i have done flyback at about 15 W and have heard of them used= in=20 the 10s of milliwatt range. I think i have seen PFC that was done with = SEPIC=20 in the 20 watt range.

Reply to
JosephKK

On Tue, 29 Dec 2009 13:44:36 GMT, Jan Panteltje = wrote:

Williams"

looks=20

do,=20

I am playing around with modeling 3-phase rectifiers. I think PFC=20 would be a real good thing for 3-phase rectifiers. May be more than=20 a tad interesting to implement though.

I am getting some interesting results. I would really like to=20 build some and measure them.

Version 4 SHEET 1 880 680 WIRE 16 -368 -112 -368 WIRE 112 -368 16 -368 WIRE 304 -368 112 -368 WIRE 336 -368 304 -368 WIRE 544 -368 336 -368 WIRE -112 -288 -112 -368 WIRE 16 -288 16 -368 WIRE 112 -288 112 -368 WIRE 336 -192 336 -368 WIRE -384 -176 -768 -176 WIRE -768 -144 -768 -176 WIRE -384 -144 -384 -176 WIRE -192 -144 -288 -144 WIRE -112 -144 -112 -224 WIRE -112 -144 -192 -144 WIRE -768 -64 -832 -64 WIRE -384 -64 -480 -64 WIRE -192 -64 -288 -64 WIRE -384 0 -768 0 WIRE -768 32 -768 0 WIRE -384 32 -384 0 WIRE -144 32 -288 32 WIRE 16 32 16 -224 WIRE 16 32 -144 32 WIRE 544 32 544 -368 WIRE -192 64 -192 -64 WIRE 336 64 336 -128 WIRE 336 64 -192 64 WIRE 352 64 336 64 WIRE -832 112 -832 -64 WIRE -768 112 -832 112 WIRE -480 112 -480 -64 WIRE -384 112 -480 112 WIRE -192 112 -192 64 WIRE -192 112 -288 112 WIRE -384 176 -768 176 WIRE -768 192 -768 176 WIRE -384 208 -384 176 WIRE -144 208 -288 208 WIRE 112 208 112 -224 WIRE 112 208 -144 208 WIRE 352 240 352 64 WIRE -240 288 -288 288 WIRE -192 288 -192 112 WIRE -192 288 -240 288 WIRE -832 320 -832 112 WIRE -768 320 -768 272 WIRE -768 320 -832 320 WIRE -736 320 -768 320 WIRE -480 320 -480 112 WIRE -480 320 -736 320 WIRE -384 320 -384 288 WIRE -384 320 -480 320 WIRE -192 368 -192 288 WIRE -112 368 -112 -144 WIRE 16 368 16 32 WIRE 112 368 112 208 WIRE -736 528 -736 320 WIRE -560 528 -736 528 WIRE -240 528 -240 288 WIRE -240 528 -480 528 WIRE -112 528 -112 432 WIRE 16 528 16 432 WIRE 16 528 -112 528 WIRE 112 528 112 432 WIRE 112 528 16 528 WIRE 320 528 112 528 WIRE 352 528 352 304 WIRE 352 528 320 528 WIRE 544 528 544 112 WIRE 544 528 352 528 =46LAG -192 368 0 =46LAG -192 -144 A =46LAG -144 32 B =46LAG -144 208 C =46LAG 304 -368 V- =46LAG 320 528 V+ SYMBOL ind2 -400 -160 R0 SYMATTR InstName L1 SYMATTR Value 20m SYMATTR Type ind SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL ind2 -272 -48 R180 WINDOW 0 36 80 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName L2 SYMATTR Value 20m SYMATTR Type ind SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL ind2 -400 16 R0 SYMATTR InstName L3 SYMATTR Value 20m SYMATTR Type ind SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL ind2 -272 128 R180 WINDOW 0 36 80 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName L4 SYMATTR Value 20m SYMATTR Type ind SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL ind2 -400 192 R0 SYMATTR InstName L5 SYMATTR Value 20m SYMATTR Type ind SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL ind2 -272 304 R180 WINDOW 0 36 80 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName L6 SYMATTR Value 20m SYMATTR Type ind SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL diode -128 -288 R0 SYMATTR InstName D1 SYMATTR Value MUR460 SYMBOL diode 0 -288 R0 SYMATTR InstName D2 SYMATTR Value MUR460 SYMBOL diode 96 -288 R0 SYMATTR InstName D3 SYMATTR Value MUR460 SYMBOL diode -128 368 R0 SYMATTR InstName D4 SYMATTR Value MUR460 SYMBOL diode 0 368 R0 SYMATTR InstName D5 SYMATTR Value MUR460 SYMBOL diode 96 368 R0 SYMATTR InstName D6 SYMATTR Value MUR460 SYMBOL res 528 16 R0 SYMATTR InstName R1 SYMATTR Value 100 SYMBOL voltage -768 -160 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value SINE(0 120 60 0 0 0) SYMBOL voltage -768 16 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value SINE(0 120 60 0 0 120) SYMBOL voltage -768 176 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value SINE(0 120 60 0 0 240) SYMBOL res -464 512 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value 1G SYMBOL cap 320 -192 R0 SYMATTR InstName C1 SYMATTR Value 1000? SYMATTR SpiceLine V=3D250 Irms=3D20 Rser=3D.5 Lser=3D20u SYMBOL cap 336 240 R0 SYMATTR InstName C2 SYMATTR Value 1000? SYMATTR SpiceLine V=3D250 Irms=3D20 Rser=3D.5 Lser=3D20u TEXT -552 -128 Left 0 !k12 L1 L2 .98 TEXT -560 72 Left 0 !k34 L3 L4 .98 TEXT -552 232 Left 0 !K56 L5 L6 .98 TEXT -640 416 Left 0 !.tran 0 300m 0 10u

And

Version 4 SHEET 1 880 680 WIRE 16 -368 -112 -368 WIRE 112 -368 16 -368 WIRE 176 -368 112 -368 WIRE 304 -368 256 -368 WIRE 336 -368 304 -368 WIRE 464 -368 336 -368 WIRE 544 -368 464 -368 WIRE -112 -288 -112 -368 WIRE 16 -288 16 -368 WIRE 112 -288 112 -368 WIRE 336 -192 336 -368 WIRE -384 -176 -768 -176 WIRE 464 -176 464 -368 WIRE -768 -144 -768 -176 WIRE -384 -144 -384 -176 WIRE -192 -144 -288 -144 WIRE -112 -144 -112 -224 WIRE -112 -144 -192 -144 WIRE -112 -128 -112 -144 WIRE 160 -128 -112 -128 WIRE 272 -128 240 -128 WIRE -768 -64 -832 -64 WIRE -384 -64 -480 -64 WIRE -192 -64 -288 -64 WIRE -384 0 -768 0 WIRE 272 0 272 -128 WIRE 464 0 464 -96 WIRE 464 0 272 0 WIRE -768 32 -768 0 WIRE -384 32 -384 0 WIRE -192 32 -192 -64 WIRE -192 32 -288 32 WIRE -144 32 -192 32 WIRE 16 32 16 -224 WIRE 16 32 -144 32 WIRE 160 32 16 32 WIRE 272 32 272 0 WIRE 272 32 240 32 WIRE 544 32 544 -368 WIRE 464 48 464 0 WIRE 464 48 416 48 WIRE 336 64 336 -128 WIRE 352 64 336 64 WIRE -832 112 -832 -64 WIRE -768 112 -832 112 WIRE -480 112 -480 -64 WIRE -384 112 -480 112 WIRE -192 112 -288 112 WIRE 464 160 464 48 WIRE -384 176 -768 176 WIRE -768 192 -768 176 WIRE -384 208 -384 176 WIRE -192 208 -192 112 WIRE -192 208 -288 208 WIRE -144 208 -192 208 WIRE 112 208 112 -224 WIRE 112 208 -144 208 WIRE 160 208 112 208 WIRE 272 208 272 32 WIRE 272 208 240 208 WIRE 352 240 352 64 WIRE -112 288 -112 -128 WIRE -112 288 -288 288 WIRE -832 320 -832 112 WIRE -768 320 -768 272 WIRE -768 320 -832 320 WIRE -736 320 -768 320 WIRE -480 320 -480 112 WIRE -480 320 -736 320 WIRE -384 320 -384 288 WIRE -384 320 -480 320 WIRE -112 368 -112 288 WIRE 16 368 16 32 WIRE 112 368 112 208 WIRE -736 528 -736 320 WIRE -560 528 -736 528 WIRE -336 528 -480 528 WIRE -240 528 -336 528 WIRE -112 528 -112 432 WIRE 16 528 16 432 WIRE 16 528 -112 528 WIRE 112 528 112 432 WIRE 112 528 16 528 WIRE 192 528 112 528 WIRE 320 528 272 528 WIRE 352 528 352 304 WIRE 352 528 320 528 WIRE 464 528 464 240 WIRE 464 528 352 528 WIRE 544 528 544 112 WIRE 544 528 464 528 WIRE -336 576 -336 528 WIRE -240 592 -240 528 WIRE 416 592 416 48 WIRE 416 592 -240 592 =46LAG -192 -144 A =46LAG -144 32 B =46LAG -144 208 C =46LAG 304 -368 V- =46LAG 320 528 V+ =46LAG -336 576 0 SYMBOL ind2 -400 -160 R0 SYMATTR InstName L1 SYMATTR Value 20m SYMATTR Type ind SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL ind2 -272 -48 R180 WINDOW 0 36 80 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName L2 SYMATTR Value 40m SYMATTR Type ind SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL ind2 -400 16 R0 SYMATTR InstName L3 SYMATTR Value 20m SYMATTR Type ind SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL ind2 -272 128 R180 WINDOW 0 36 80 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName L4 SYMATTR Value 40m SYMATTR Type ind SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL ind2 -400 192 R0 SYMATTR InstName L5 SYMATTR Value 20m SYMATTR Type ind SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL ind2 -272 304 R180 WINDOW 0 36 80 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName L6 SYMATTR Value 40m SYMATTR Type ind SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL diode -128 -288 R0 SYMATTR InstName D1 SYMATTR Value MUR460 SYMBOL diode 0 -288 R0 SYMATTR InstName D2 SYMATTR Value MUR460 SYMBOL diode 96 -288 R0 SYMATTR InstName D3 SYMATTR Value MUR460 SYMBOL diode -128 368 R0 SYMATTR InstName D4 SYMATTR Value MUR460 SYMBOL diode 0 368 R0 SYMATTR InstName D5 SYMATTR Value MUR460 SYMBOL diode 96 368 R0 SYMATTR InstName D6 SYMATTR Value MUR460 SYMBOL res 528 16 R0 SYMATTR InstName R1 SYMATTR Value 100 SYMBOL voltage -768 -160 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value SINE(0 120 60 0 0 0) SYMBOL voltage -768 16 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value SINE(0 120 60 0 0 120) SYMBOL voltage -768 176 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value SINE(0 120 60 0 0 240) SYMBOL res -464 512 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value 1G SYMBOL cap 320 -192 R0 SYMATTR InstName C1 SYMATTR Value 1000? SYMATTR SpiceLine V=3D250 Irms=3D20 Rser=3D.5 Lser=3D20u SYMBOL cap 336 240 R0 SYMATTR InstName C2 SYMATTR Value 1000? SYMATTR SpiceLine V=3D250 Irms=3D20 Rser=3D.5 Lser=3D20u SYMBOL ind 160 -352 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 5 56 VBottom 0 SYMATTR InstName L7 SYMATTR Value 200n SYMATTR SpiceLine Ipk=3D10 Rser=3D,5 SYMBOL res 448 -192 R0 SYMATTR InstName R2 SYMATTR Value 1000 SYMBOL res 448 144 R0 SYMATTR InstName R4 SYMATTR Value 1000 SYMBOL ind 176 544 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 5 56 VBottom 0 SYMATTR InstName L8 SYMATTR Value 200n SYMATTR SpiceLine Ipk=3D10 Rser=3D.5 SYMBOL res 256 -144 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R5 SYMATTR Value 2k SYMBOL res 256 16 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R6 SYMATTR Value 2k SYMBOL res 256 192 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R7 SYMATTR Value 2k TEXT -552 -128 Left 0 !k12 L1 L2 .98 TEXT -560 72 Left 0 !k34 L3 L4 .98 TEXT -552 232 Left 0 !K56 L5 L6 .98 TEXT -640 416 Left 0 !.tran 0 200m 0 10u

Reply to
JosephKK

looks

they do,

Not only that, i tripped over an alternate reading.

Reply to
JosephKK

The ordinary 3 phase 6 pulse rectifier is a quite nasty polluter of the mains.

To reduce the harmonics, 12 pulse rectifiers have been used, with one set of rectifiers connected to the wye windings and the other set from separate delta windings. For high power systems, you still are going to need a medium/low voltage transformer on site, so it is not a big deal having separate wye and delta secondary windings on that transformer.

If you want to get away with the heavy 50 Hz transformer, there seems to be various more or less patented 3 phase systems using flyback etc. systems to reduce the PFC, but these seems to be hugely complex and have special floating requirements for the DC side.

If floating output or voltages other than those obtainable by simple rectifiers are required, it might be easier to simply get three single phase SMPS with PFC at the input and connect the DC outputs in parallel.

If the input voltage ratings permit, instead of wye, connect the inputs into delta to avoid any mains neutral polluting and also allow higher voltage and hence higher power (1.7x) for a specific semiconductor amperage.

Reply to
Paul Keinanen

Paul Keinanen a écrit :

For Tim, which I suspect is asking this for his induction heater, it might be easier to use his bridge so as to draw sine current.

The output power will be sine squared but who cares? And that'll put more requirement on some components for the same average output power, but it'll avoid a full PFC stage which won't do good on efficiency, and this might have a higher overall efficiency.

--
Thanks,
Fred.
Reply to
Fred Bartoli

Yup. But it's also a good general question.

I may do this, and it even makes the coil hum with a pleasing growl. The downside is it puts 120Hz into all my loop, and makes scoping the inverter fairly useless. Constant current mode would have to be slower than 120Hz, and I'm not sure how 120Hz will affect the PLL.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Reply to
Tim Williams

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.