Connect with us

Power factor correction

Discussion in 'Electronic Design' started by Tim Williams, Dec 29, 2009.

Scroll to continue with content
  1. Tim Williams

    Tim Williams Guest

    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
     
  2. Phil Allison

    Phil Allison Guest

    "Tim Williams"
    ** Come back when you sober up.

    Fuckhead.




    .... Phil
     
  3. Hammy

    Hammy Guest

    They use CCM Boost topology for PFC.

    See NCP1654 for example.

    http://www.onsemi.com/PowerSolutions/product.do?id=NCP1654
     
  4. Hammy

    Hammy Guest

  5. Fred Bartoli

    Fred Bartoli Guest

    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.
     
  6. Tim Williams

    Tim Williams Guest

    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
     
  7. Tim Williams

    Tim Williams Guest

    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
     
  8. Alan W

    Alan W Guest

    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
     
  9. Tim Williams

    Tim Williams Guest

    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
     
  10. JosephKK

    JosephKK Guest

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

    JosephKK Guest

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

    I am getting some interesting results. I would really like to
    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
    FLAG -192 368 0
    FLAG -192 -144 A
    FLAG -144 32 B
    FLAG -144 208 C
    FLAG 304 -368 V-
    FLAG 320 528 V+
    SYMBOL ind2 -400 -160 R0
    SYMATTR InstName L1
    SYMATTR Value 20m
    SYMATTR Type ind
    SYMATTR SpiceLine Ipk=10 Rser=.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=10 Rser=.5
    SYMBOL ind2 -400 16 R0
    SYMATTR InstName L3
    SYMATTR Value 20m
    SYMATTR Type ind
    SYMATTR SpiceLine Ipk=10 Rser=.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=10 Rser=.5
    SYMBOL ind2 -400 192 R0
    SYMATTR InstName L5
    SYMATTR Value 20m
    SYMATTR Type ind
    SYMATTR SpiceLine Ipk=10 Rser=.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=10 Rser=.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=250 Irms=20 Rser=.5 Lser=20u
    SYMBOL cap 336 240 R0
    SYMATTR InstName C2
    SYMATTR Value 1000?
    SYMATTR SpiceLine V=250 Irms=20 Rser=.5 Lser=20u
    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
    FLAG -192 -144 A
    FLAG -144 32 B
    FLAG -144 208 C
    FLAG 304 -368 V-
    FLAG 320 528 V+
    FLAG -336 576 0
    SYMBOL ind2 -400 -160 R0
    SYMATTR InstName L1
    SYMATTR Value 20m
    SYMATTR Type ind
    SYMATTR SpiceLine Ipk=10 Rser=.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=10 Rser=.5
    SYMBOL ind2 -400 16 R0
    SYMATTR InstName L3
    SYMATTR Value 20m
    SYMATTR Type ind
    SYMATTR SpiceLine Ipk=10 Rser=.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=10 Rser=.5
    SYMBOL ind2 -400 192 R0
    SYMATTR InstName L5
    SYMATTR Value 20m
    SYMATTR Type ind
    SYMATTR SpiceLine Ipk=10 Rser=.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=10 Rser=.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=250 Irms=20 Rser=.5 Lser=20u
    SYMBOL cap 336 240 R0
    SYMATTR InstName C2
    SYMATTR Value 1000?
    SYMATTR SpiceLine V=250 Irms=20 Rser=.5 Lser=20u
    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=10 Rser=,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=10 Rser=.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
     
  12. JosephKK

    JosephKK Guest

    Not only that, i tripped over an alternate reading.
     
  13. 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.
     
  14. Fred Bartoli

    Fred Bartoli Guest

    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.
     
  15. Tim Williams

    Tim Williams Guest

    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
     
  16. Tim Williams

    Tim Williams Guest

    And of course, since you have two phases on two wires (let the other be
    common), you have a linearly independent basis (not orthonormal, but so
    what) from which you can span the entire vector space of voltage and phase.
    So you could, for example, produce a 5-phase system with 10 pulses, or 120
    if you wanted. You spend a lot on transformers, though.

    What does that do for current, anyway? Current through each phase is
    essentially a parabolic pulse. All those added up, in the ratios from which
    they are generated, should distribute to a fairly constant current,
    shouldn't they? Well, the sum of (three phase) currents is always zero, but
    the sum of magnitudes isn't: that must oscillate at the 6th harmonic. So it
    should be that, in the same way as a choke input filter causes relatively
    more current draw on the flanks of the sine wave than overall, this
    arrangement also causes more current draw on the flanks, resulting in an
    inversely phased 6th harmonic. The curious part is, this nonlinear
    conclusion was based on the linear construction of vectors: of course the
    diodes, being nonlinear elements, are the reason, but the voltages don't
    seem like they should do that.

    Tim
     
  17. Tim Williams

    Tim Williams Guest

    How can there ever not be harmonics, either voltage or current, input or
    output, when transforming three phase to DC? I think a simple energy budget
    shows this is necessary.

    Ignoring the three phase source, if you start with n equal voltage, equally
    spaced phases, you will get harmonics of 2n and higher, with a current pulse
    roughly 1/n of the waveform per phase.

    Tim
     
  18. Digging deeper into my old archives, the ON Semi PFC Handbook
    http://www.onsemi.com/pub_link/Collateral/HBD853-D.PDF might also be
    useful for single phase applications up to 300 W.
     
  19. krw

    krw Guest

    I love the smell of burning selenium in the morning.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-