Inverters - true or modified sine wave?

SystemSystem Posts: 2,511 admin
It seems from my research that modified sine wave inverters tend to cost a lot less, and they are more energy efficient in converting DC to AC. That sounds good.

The downside is always fuzzy -- "some things might not work right", with few examples given. There are also lots of anecdotal reports of electronic failings being blamed on modified sine wave inverters - but it also could just be people looking for reasons to explain why stuff broke.

The AC loads we have tend to be two laptops, a second LCD monitor, LED Christmas lights, a blender (frozen drinks!), various rechargers for tools or toys, and perhaps in the new trailer we will have a microwave to fire up on occasion. We also may ditch the automotive AV system and stick in a Sony "home theater in a box" for surround sound.

I do wonder if the AV gear might suffer from the MSW... But with the rest, is there really any downside?

What are the real advantages of going with a sine wave inverter?

And does the quality of the modified sine wave inverter make a difference? Are there some models or brands better than others?

- Chris // www.technomadia.com

Comments

  • mike95490mike95490 Solar Expert Posts: 9,361 ✭✭✭✭✭
    Re: Inverters - true or modified sine wave?
    It seems from my research that modified sine wave inverters tend to cost a lot less, and they are more energy efficient in converting DC to AC. That sounds good.

    Till you connect some coil driven appliance (wall wart with iron core transformer) and then the coil draws 20% extra power from the inverter, which is why, sometimes, things fry. If you are using switch mode power supplies (light weight wall warts or power line bricks), they simply rectify the AC, and run it thru a 400KHz transformer, which is very small, light, and efficient. Most things with an iron core, won't like mod-sine inverters.
    Some rechargers for power tools work fine, and some die nearly instantly. I know the older Makita chargers work fine on mod-sine, we used them for days in the heat, building camps in the desert.
    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 ,

  • System2System2 Posts: 6,290 admin
    Re: Inverters - true or modified sine wave?

    In general, induction motors draw an extra 20% power, and run hotter. If only run for short time, before they get hot, probably not a big problem except for the extra power consumption. Longer running motors, such as fridge / freezer compressors will have a greatly shortened life. The windings tend to vibrate excessively as well in motors, with the possibility of wearing through their thin insulation.
    One other problem is with "capacitor run" motors, which are in better quality items from breadmakers to fans and high efficiency fridge/ freezers etc. On normal pure sinewave power, the capacitors modify and control the currents through certain of the motor windings. However, when run on MSW, the nature of capacitors cause them to "pass" excessive currents, because of the sharp edges and spikes in the MSW supply. This results in excessive buzzing, poor performance and overheating. It is this same characteristic of capacitors that results in the burning out of some electronic items, ranging from breadmakers to some chargers and many other items. The excessive currents "passed" by the capacitors in some power supply designs, (when operated on MSW) result in overheating that burns out components on the circuit boards. In these cases, you MAY detect a hot or burning smell before the item fails, but most times, the smell comes after the fact. How do you know if your item will survive on MSW? Trial and error. Throw the dice and take your chances.
    In general, CFL lights work fine on MSW, as do most items with "universal, brush type" motors, such as skillsaws, electric drills, angle grinders and hedge trimmers, as these motors traditionally will operate on anything you feed them, AC, DC, or pulsed. The exceptions may be those with electronic controls, although the variable speed controls on drills and jigsaws tend to work fine.
    In general, you will find that battery chargers for cordless items, if they don't burn out, will not properly charge the battery. Probably because of the substantially lower peak voltage from MSW inverters. Yes, the "average" voltage is close to that of pure sine, but the "peak" voltage is much lower.
    Microwaves tend to hum loudly, basically sound sick, and have much lower heating power. Again, the electronics in the clock / timer / controls, depending on the design of their power supply may burn out in short order. Roll the dice to find out.
    This post isn't BS. I've been there, done that and experienced it all.
    Hope this helps.
    Wayne
  • nigtomdawnigtomdaw Solar Expert Posts: 705 ✭✭
    Re: Inverters - true or modified sine wave?

    Looking at your website and your full time off grid lifestyle at the moment its a no brainer go Pure Sinewave. If you dont by the time you realise you should have you will have spent the difference in new replacement electrical equipment anyway. Even laptop batteries dont like MSW because they never get fully charged on MSW at least the two I used never would show at 100% charged and both these laptops batteries failed prematurely.

    MSW has its place and price like everything else but not in a 24/7 off grid likestyle that you have chosen IMHO
  • Solar GuppySolar Guppy Solar Expert Posts: 1,973 ✭✭✭
    Re: Inverters - true or modified sine wave?
    It seems from my research that modified sine wave inverters tend to cost a lot less, and they are more energy efficient in converting DC to AC. - Chris // www.technomadia.com


    They cost less but I have yet to find one that is more efficient.

    The Xantrex XW series is better than 95% for pure sinewave ... I have never seen a Modsine with that type of efficiency.
  • System2System2 Posts: 6,290 admin
    Re: Inverters - true or modified sine wave?

    Really, other than price, the only thing many MSW inverters have going for them is usually a lower idle power draw. That said, many of the newer ones don't seem all that great. As to older ones, I have several Statpower 250 watt MSW units with, believe it or not, an idle current draw of just 20ma, but it is electrically (RFI) one noisy son-of-a-gun, and can only be used for compatible loads. I use it during the short dark days of winter, on 24/7 for CFL's etc, but come Spring, on comes the 6 watt idle, Puresine 300, 24/7 instead of the Statpower.
    Wayne
  • mike95490mike95490 Solar Expert Posts: 9,361 ✭✭✭✭✭
    Re: Inverters - true or modified sine wave?

    For life in your trailer, I'd strongly suggest the Morningstar SureSine, 300watt cont, 600w 5 min surge, High efficiency. Very new design, no bad reports about it.
    http://www.morningstarcorp.com/products/SureSine/index.shtml
    $300 and a 2 year warranty to boot!

    And keep your old inverter to use with the bigger loads
    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 ,

  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Inverters - true or modified sine wave?
    mike90045 wrote: »
    For life in your trailer, I'd strongly suggest the Morningstar SureSine, 300watt cont, 600w 5 min surge, High efficiency. Very new design, no bad reports about it.
    http://www.morningstarcorp.com/products/SureSine/index.shtml
    $300 and a 2 year warranty to boot!

    And keep your old inverter to use with the bigger loads

    Ditto,

    I have been using one for about a year now. I love it. It does induce some Rf into the AM radio band however. (Not that I listen to AM much). The other nice thing is that unlike most small inverters, you can wire it to a grounded neutral, in a house wiring situation. Most small inverters will fry if you try that.

    Icarus
  • System2System2 Posts: 6,290 admin
    Re: Inverters - true or modified sine wave?
    mike90045 wrote: »
    For life in your trailer, I'd strongly suggest the Morningstar SureSine, 300watt cont, 600w 5 min surge, High efficiency. Very new design, no bad reports about it.
    http://www.morningstarcorp.com/products/SureSine/index.shtml
    $300 and a 2 year warranty to boot!

    That is a nice little inverter. I like that it manages to do without a cooling fan.

    But - I do want an inverter with an integrated transfer switch to pass through AC when I am connected to shore power. I do not want to deal with the complexity of only having certain inverter-powered outlets.

    Any recommendations or opinions on something like the PureSine 2.0 or the inverter / chargers from Magnum?

    - Chris // www.technomadia.com
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Inverters - true or modified sine wave?

    Spend the extra money for a true sine. It will be better in the long run.



    OT: I also have a diesel Jeep. Love it except for the EGR problems.
  • System2System2 Posts: 6,290 admin
    Re: Inverters - true or modified sine wave?

    I love my 2 Puresine 300's. Very impressed with them.
    As to switching to shore power, a simple relay, with it's coil powered from the line from shore, could easily be wired to automatically switch the loads from inverter to shore, whenever shore power presents itself to the relay coil.
    When the shore power vanishes for any reason, the relay snaps the loads back to inverter.
    Re microwave, if you intend to run that, you will meed a big (at the very least 1500 watt) pure sine inverter. Consider the value of running the microwave vs the extra costs for inverter, as well as the much larger idle current of that larger inverter, if you decide to use it to power small loads. Or have 2 inverters. A small one on 24/7 for lights etc and the big one only on to run the micro.
    Wayne
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Inverters - true or modified sine wave?
    That is a nice little inverter. I like that it manages to do without a cooling fan.

    But - I do want an inverter with an integrated transfer switch to pass through AC when I am connected to shore power. I do not want to deal with the complexity of only having certain inverter-powered outlets.

    Any recommendations or opinions on something like the PureSine 2.0 or the inverter / chargers from Magnum?

    - Chris // www.technomadia.com


    Iota makes a very nice automatic transfer switch: http://store.solar-electric.com/ioitauactrsw.html

    This is what I use to transfer between generator (shore) power and battery inverter power. I have one outlet wired in the house that is live only when the generator is running. This is for the Xantrex battery charger. If I had to do it a again, I would wire one additional outlet to run power tools off the generator. One of quirks of the relay is that if the generator voltage drops, it switches back to the inverter. The starting load of a large saw will drop the voltage momentarily so that it will revert back to the inverter, so plugging in on the generator side helps with the problem.

    It is a very simple matter to wire in the transfer switch to feed from either source, then through the breaker panel to the branch circuits. With the exception of the above problem, the system works flawlessly and seamlessly.

    Icarus
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