Modified vs Pure Sine Wave

Steven LakeSteven Lake Solar Expert Posts: 402 ✭✭
Hi all. I've got a question I thought you could help me solve. Especially since your experience has proven very useful. :) A friend of mine on Facebook, in talking about the recent northeast power outages, said that it's best to avoid an inverter with modified sine wave, instead preferring one with pure sine wave as pure doesn't destroy electronics, whereas modified does. Sure, it doesn't do it all at once, but apparently, per him, given a couple weeks running a PC on a modified sine wave inverter it will destroy the power supply. Is there any truth to that, or is he just blowing smoke? I'm just wondering as I haven't seen the same thing on my end and I run a lot of modsine inverters. But then again, most of the stuff I run via inverter tends to be pretty rugged and not likely to be affected by things like that, or else it's safely tucked behind a UPS. So I may be partially sheltered from the effects, and thus I'm not seeing them.

Comments

  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Modified vs Pure Sine Wave

    Most computer UPS's actually produce Modified Sine output. It's the small cheap supplies: camera charger wall warts, stuff like that that sometimes gets fried.
    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 ,

  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Modified vs Pure Sine Wave

    Many things will work perfectly well on MSG throughout their normal expected lifetime. A few items however, using designs that work perfectly well on normal grid power, don't like MSW and some critical internal parts will overheat to the point of being destroyed. Which items will work fine and which will fail is sort of like playing Russian Roulette. You basically have to risk it, try it, and see what happens.
    Other things are known, like the fact that induction motors can draw roughly 18% more power, resulting in raised temperatures which may cause damage, but will definitely waste power. These raised temperatures can be critical to refrigerator and freezer compressors and have been known to cut short their lives. There is another motor problem, and that's the excess vibration in the windings caused by sharp pulsing of the magnetic fields caused by the MSW, a vibration that can wear down the insulating within the windings, resulting in shorted windings.
    So it depends on what use the MSW is put to whether the results will be fine - - or not.
    In the past, before I switched to pure sine, I did burn out the power supplies in the electronics of two bread makers, and found that rechargeable drills would not recharge properly. Other than that, there were no problems.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Modified vs Pure Sine Wave
    So it depends on what use the MSW is put to whether the results will be fine - - or not.
    In the past, before I switched to pure sine, I did burn out the power supplies in the electronics of two bread makers, and found that rechargeable drills would not recharge properly. Other than that, there were no problems.

    I did a similar thing to one of my 2 DeWalt battery charges. They both still work but one of them will only give a partial charge relative tot the other and takes longer to charge... so something is partially damaged inside.. I noticed a 'burnt wire' smell and unplugged it and went and bought a TSW inverter...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
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    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • techntrektechntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Modified vs Pure Sine Wave

    I read a study done by a major computer magazine in the early-mid 90's, where they tested dozens of computer power supplies with all kinds of dirty power. Too high, too low, off-frequency, pulsed, etc. No issues. Now-a-days most consumer electronics (tvs, dvrs, stereos) have either the same type or switching power supplies, which will take anything short of a lightning strike.

    Personally the only thing I found that almost fried on MSW was an X10 controller. Others have mentioned problems with shavers.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • BB.BB. Super Moderators, Administrators Posts: 32,800 admin
    Re: Modified vs Pure Sine Wave

    I have tried small DVD player with the wall transformer (or electronics)--And it did not like MSW inverters (got hot).

    Larger desktop computers made in the last few years can probably take MSW power (aka Power Factor Corrected Supplies)--Smaller laptop computer may have the older rectifier+diode bridge type (smaller power supplies are not required by regulation to have PFC), and may overheat on MSW power.

    In general, I would use a Kill-a-Watt meter and look at the Power Factor when the device is plug in to utility power... If the PF>0.95, it is probably power factor corrected (which can do fine with MSW). If the PF is less than 0.80, I would worry.

    HOWEVER--One person here did have, apparently, a PFC power supply and it still failed on MSW... There are just so many ways of doing things, it is almost impossible to make any sort of general statements.

    If you have poor power factor--Then the "extra current" has to go somewhere (part is wasted as heat), and the sharp edges of MSW can cause even higher peak currents, which because of I^2*R heating, if the peak current doubles, the self heating goes up by 4x.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Steven LakeSteven Lake Solar Expert Posts: 402 ✭✭
    Re: Modified vs Pure Sine Wave

    Okay, so basically he was right, but only to the point that it's a total crapshoot when it comes to what will and what won't go boom on MSW. Gotcha. Sounds reasonable enough. Now, secondary question. Is there any kind of line conditioner plugins you can put between a MSW inverter and your item in question to soften the signal from MSW to pure, or at least something less "water hammerish" in its nature?
  • BB.BB. Super Moderators, Administrators Posts: 32,800 admin
    Re: Modified vs Pure Sine Wave

    Nope.... Nothing practical.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • AceNZAceNZ Solar Expert Posts: 104 ✭✭✭✭
    Re: Modified vs Pure Sine Wave
    Is there any kind of line conditioner plugins you can put between a MSW inverter and your item in question to soften the signal from MSW to pure, or at least something less "water hammerish" in its nature?

    You could use a bank of batteries with a charge controller and a sine wave inverter....
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    Re: Modified vs Pure Sine Wave
    Now, secondary question. Is there any kind of line conditioner plugins you can put between a MSW inverter and your item in question to soften the signal from MSW to pure, or at least something less "water hammerish" in its nature?

    You can:

    1) use a ferroresonant transformer to pass only 60Hz (huge, expensive, generally impractical)
    2) use a non-resonant low pass filter to reduce some of the harmonics (very hard on inverters, not too efficient, large)
    3) use a motor/generator (loud, heavy)

    Generally it is much cheaper to just get a better inverter.
  • RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Modified vs Pure Sine Wave

    When I bought my inverters I thought about it a bit and decided I'd rather shell out a bit more for the PSW models and KNOW I'd be fine than save a few bucks on MSW, worry about my more expensive items, and possibly even have to repurchase something that went out early because of it.

    Most of the items I'm running on inverters cost more than the difference in price anyway. (I wouldn't buy the Really Cheap junk even if I did go MSW.)
  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Modified vs Pure Sine Wave
    .... Is there any kind of line conditioner plugins you can put between a MSW inverter and your item in question to soften the signal from MSW to pure, or at least something less "water hammerish" in its nature?

    Nope, either they are ineffective, or so effective they crash the inverter which can't handle the inductive load. Better to get
    the pure sine inverter and rest easy.
    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 ,

  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Modified vs Pure Sine Wave
    mike95490 wrote: »
    Nope, either they are ineffective, or so effective they crash the inverter which can't handle the inductive load. Better to get
    the pure sine inverter and rest easy.

    Exactly! Everything else is either impractical or tantamount to snake oil.
  • upa123upa123 Registered Users Posts: 17
    Re: Modified vs Pure Sine Wave

    I am another convert to the church of PSW, unfortunately it took the death of at least 3 wall wart power supplies and a furnace fan motor before I realized what was going on. The MSW also drove my furnace circuit board nuts, as it would randomly turn itself off and on without any input from the thermostat.
  • BB.BB. Super Moderators, Administrators Posts: 32,800 admin
    Re: Modified vs Pure Sine Wave

    A couple of FAQs from our host:

    All About Inverters
    Choosing an Inverter - Home Power Magazine

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