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Good, quasi-square wave UPS?

Discussion in 'Electronic Basics' started by AC/DCdude17, Sep 5, 2003.

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  1. AC/DCdude17

    AC/DCdude17 Guest

    I have a Belkin 350VA UPS with a quasi square wave output. Its output
    works ok for my computer, but it doesn't work well all with non switching
    power supply load. An incandescent lamp flickers badly. A fluorescent
    lighting with inductive input(magnetic ballast or commercial grade
    electronic) causes the ballast and UPS to make a noise that sounds like
    resonating and flickers very badly. The output waveform is very elastic
    and it jumps around on the scope screen.

    The output waveform on my 300W quasi squarewave inverter is much rigid
    and it has no problem running non-switching power supply loads.

    Is there a quasi-square wave UPS that can at least stably power anything
    my power inverter can?

    By the way, there is a dead obvious difference in the inverter circuit
    between the two. The power inverter uses a few ferrite core high
    frequency transformers. The Belkin UPS have a low frequency steel core
    transformer that is used for both charging and inverter transformer.
     
  2. You didn't specify the waveform very well. You could try using a low pass
    filter that cuts out harmonics. If the waveform is symmetrical + & -, the
    first significant harmonic will be the third or 180 Hz. I would think that
    the criterion will be cost.

    There are companies in the business of filtering harmonics.

    Bill
     
  3. the Wiz

    the Wiz Guest

    Most iron-core transformer inverters don't work well with inductive or high
    power factor loads. This isn't a limited to small inverters. Some of the big
    switching power supplies (Cisco routers and switches) specifically mention that
    they should not be run from certain classes of inverters because of the
    inverter's inability to handle the switching supply load. The 40KVA UPS at the
    network lab I worked in a couple of years ago provided a modified sine wave
    output. The UPS used 400+ volts of NiMH cells as the power source until the
    backup diesel generators could be started and take the load.

    If you buy better equipment (stepped sine wave or sine wave), then the waveform
    is better and the ability to handle non-resistive loads improves greatly. Of
    course, you will pay several times more per watt of output than you do for the
    simple inverters.

    I use small UPS's (including a Belkin 350) for graceful desktop PC shutdown and
    an APC 180 for the local network (DSL modem, router, switch). The APC provides
    over an hour of run time for the network equipment. Rechargeable power failure
    lights provide immediate light during short power outages (plus battery powered
    lanterns) and oil lamps plus a Coleman lantern handle longer outages.

    If really pressed for power, I have a small inverter that can be powered from a
    12 volt vehicle.

    More about me: http://thelabwiz.home.mindspring.com/
    VB3 source code: http://thelabwiz.home.mindspring.com/vbsource.html
    VB6 source code: http://thelabwiz.home.mindspring.com/vb6source.html
    VB6 - MySQL how to: http://thelabwiz.home.mindspring.com/mysql.html
    My newest language - NSBasic for the Palm PDA: http://thelabwiz.home.mindspring.com/nsbsource.html
    Drivers for Pablo graphics tablet and JamCam cameras: http://home.earthlink.net/~mwbt/
    johnecarter atat mindspring dotdot com. Fix the obvious to reply by email.
     
  4. the Wiz

    the Wiz Guest

    Interesting problem. My Belkin 350VA has a slight intermittent flicker in the
    first 20 seconds or so of powering a 40 watt incandescent bulb (only available
    lamp for testing - the UPS is w-a-y under the desk), but then the power is
    stable.

    More about me: http://thelabwiz.home.mindspring.com/
    VB3 source code: http://thelabwiz.home.mindspring.com/vbsource.html
    VB6 source code: http://thelabwiz.home.mindspring.com/vb6source.html
    VB6 - MySQL how to: http://thelabwiz.home.mindspring.com/mysql.html
    My newest language - NSBasic for the Palm PDA: http://thelabwiz.home.mindspring.com/nsbsource.html
    Drivers for Pablo graphics tablet and JamCam cameras: http://home.earthlink.net/~mwbt/
    johnecarter atat mindspring dotdot com. Fix the obvious to reply by email.
     
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