Power Factor Correcting power supplies on MSW Inverters

RCinFLARCinFLA Solar Expert Posts: 1,280 ✭✭✭
This is more of an alert thread. I was reviewing customer rating comments on computer components and ran across one that down rated a computer switching power supply because it blew out when he ran it from a modified sinewave inverter.

More and more computer power supplies are including PFC circuits. Many driven by country regulations.

Most PFC switching power supplies have a pre-switcher that assumes a sinewave input with a switching profile on the pre-switcher so it charges the main D.C. filter capacitor with a sinewave pulse shaped current profile. This gives the good power factor.

Applying a modified sinewave (modified squarewave) inverter can cause the PFC circuitry to go crazy and cause the power supply to fail.

Most small home computer UPS units use modified sinewave so they create a risk of damaging a computer PFC power supply.

Comments

  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Power Factor Correcting power supplies on MSW Inverters

    Very interesting. Thanks for the heads-up.
    Some info on PFC here:
    http://www.endpcnoise.com/cgi-bin/e/faqpfc.html
  • BB.BB. Super Moderators, Administrators Posts: 30,485 admin
    Re: Power Factor Correcting power supplies on MSW Inverters

    I wonder if the passive PFC type devices are the ones that are failing... In general, I had understood that active PFC devices do OK on MSW inverters.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Power Factor Correcting power supplies on MSW Inverters
    BB. wrote: »
    I wonder if the passive PFC type devices are the ones that are failing... In general, I had understood that active PFC devices do OK on MSW inverters.

    -Bill

    Bill you probably hit the nail on the head with that one. Makes sense. ;)
  • mike95490mike95490 Solar Expert Posts: 8,752 ✭✭✭✭✭
    Re: Power Factor Correcting power supplies on MSW Inverters

    And I would have thought the opposite, as portrayed by the Iota power supplies, which will run down to DC. (they have about .65 PF.)
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 30,485 admin
    Re: Power Factor Correcting power supplies on MSW Inverters

    Are you sure about the DC input for the Iota's? Generally this type of supplies have a rectifier diode and capacitor front end (reason for the poor power factor)... Yea, they may run on around 170 VDC--if they do not use a voltage doubler. However, I have not ever seen any normal supplies actually rated to do that.

    Active Power Factor corrected power supply can generally run the same AC or DC voltage range on their input.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,752 ✭✭✭✭✭
    Re: Power Factor Correcting power supplies on MSW Inverters

    Yep, quite sure about the Iota running on DC. Simple diode/cap at the input, no PF circuit at all. 130VDC does not give full power output, that the peaks of the 120VAC supplies
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 30,485 admin
    Re: Power Factor Correcting power supplies on MSW Inverters

    Makes sense.

    A supply with active PFC can run from ~95-264 Volts at 50/60hz or DC at full rating (or whatever their particular supported voltage range is).

    -Bill

    PS: I would not suggest running at 120 / 240 non-PFC supply at the 120 VDC input range--The manual switch (and autoswitch) supplies use a diode/cap voltage doubler on their AC input... 120-170 vdc would never get the 300+ volts that is required to operate the supply.

    -BB
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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