Schaffner Filter on MSW Inverter

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Caneman
Caneman Solar Expert Posts: 71 ✭✭✭✭
in Advanced Solar Electric Technical Forum #1
I read somewhere about a "Schaffner filter" being attached to a MSW Inverter to clean up the ac output so that it can work better with some appliances that don't work well on a square wave output inverter... anyone know anything about such a filter?
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #2
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    Re: Schaffner Filter on MSW Inverter

    Schaffner makes EMI noise filters, they won't do much - if anything - to give a better waveform.
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  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    #3
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    Re: Schaffner Filter on MSW Inverter

    Unfortunately, any passive (coils and capacitors only) filter that can significantly change the output waveform will
    also significantly reduce its available output power.

    That is, aside from maybe reducing the sharp voltage edges ever so slightly. Now that might (or might not),
    have a very slight effect on radio interference.

    Not sure exactly what products might work vs. not working if you were to filter those edges ?

    boB
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #4
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    Re: Schaffner Filter on MSW Inverter

    no filter can change the square waves or more accurately the squarewave steps into a sine wave.
    A filter would filterout some of the high frequency harmonics but most devices you will be powering they have no effect anyway.
    If you want and need a sine wave inverter you have to get one..
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #5
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    Re: Schaffner Filter on MSW Inverter
    john p wrote: »
    If you want and need a sine wave inverter you have to get one..
    John is right. It's unfortunate money wise, but there really is not any reasonable way around it.
    Oh you could have your modified square wave inverter drive and electric motor, and in turn have it turn a generator that in turn outputs sinewave. But that's not practical at all.
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #6
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    Re: Schaffner Filter on MSW Inverter

    here is something simple to try to show how the average sinwave inverter DOESENT keep accurate frequency. Connect a simple digital clock radio to one then see how far out it is in 12hrs. Note the difference. Then check again in another 12hrs Note the difference to the first reading. And it will now be so far from correct time to be useless..
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Schaffner Filter on MSW Inverter
    waynefromnscanada wrote: »
    John is right. It's unfortunate money wise, but there really is not any reasonable way around it.
    Oh you could have your modified square wave inverter drive and electric motor, and in turn have it turn a generator that in turn outputs sinewave. But that's not practical at all.

    To say the least!
    The first problem here is that induction motors don't "like" MSW and will draw more power, run hotter, not at the right speed, and have shortened life as a result. Never mind the other losses from power conversions.

    There was a time when the way you got AC from DC was to use the batteries to run a DC motor that drove an alternator.

    We're really starting to wander away from the OP's question. I think he gets the picture now.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
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    Re: Schaffner Filter on MSW Inverter

    i agree with the guys that a sine wave inverter should be gotten in the first place, but that company does carry filters that could clean up a great deal of the harmonics. this would, as i said, dissipate the power of the harmonics as heat in the filter's passive components and that's nearly 30% of the power of a modsine inverter's power. if it were to be able to eliminate all harmonics a 1000w modsine inverter would yield about 707w of usable sine wave power. that's 293w of heat, but the filter would not be 100% efficient so this wattage in the form of heat would more than likely be lower than 293w. i noticed in looking up the curves that they fail to list the 3rd harmonic and i suspect that may be because it has little attenuation and may be significant in its amplitude. the bottom line would be you still have significant thd even though it is improved.

    http://www.schaffner.com/en/products/pqharmonics/ecosinetm/product/fn-3412-ecosineTM-60hz-passive-harmonic-filters.html
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  • Caneman
    Caneman Solar Expert Posts: 71 ✭✭✭✭
    #9
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    Re: Schaffner Filter on MSW Inverter

    LOL, you guys are great! I guess you don't get something for nothing... the idea was to be able to use a MSW inverter with my LG washing machine, which has a low power start, claims uber efficiency, etc., but the electronics needed a better wave form to work properly... these harmonic filters cost in the hundreds of dollars, so in the end you might as well buy the PSW...
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #10
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    Re: Schaffner Filter on MSW Inverter

    these harmonic filters cost in the hundreds of dollars, so in the end you might as well buy the PSW... YES and they are not designed to "fix" stepped square waves only to cure harmonics in "dirty" sine waves
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