What is the difference between the two?

VanDeusen
VanDeusen Solar Expert Posts: 129 ✭✭✭✭✭
Can someone tell me what is the actual difference between PUR SINE WAVE and MODIFIED SINE WAVE and which do you prefer? I have a 5000 watt modified sine that I have been using to power my house (90% off grid) and do notice that my 50" plasma tv has a wine in it that my 32" or 27" doesnt. I was told that is because its a modified and was also told that I didnt really need 5000 watts so If I went with a PURE sine then I can get one that is half as big (2500 watt) and that the pure is equavilent to the 5000 modified so I am asking here what do you think?



Also, does the pure draw LESS then the modified when its idle?

Thank you

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: What is the difference between the two?

    From NAWS Inverter FAQ's:

    All About Inverters
    Choosing an inverter for water pumping

    From times past--I guess TSW inverters were less efficient than MSW. Now-a-days--I am not so sure.

    If your loads are motors, they will consume upwards of 20% or so more energy (and dissipate it as heat--i.e., motors will run hot) on MSW inverters.

    Some 80% of devices out there will run OK on MSW (if a bit less efficient). And some 20% of devices out there will fail or have a significantly shorter life (sometimes measured in hours).

    Small AC Wall Wart Transformers and DC power converters tend run very hot on MSW inverters.

    Also, the MSW wave form has lower "peak voltage"--some florescent light fixtures may not start as well on MSW.

    And many devices will have a 120 Hz "buzz" because of the MSW waveform.

    MSW inverters, typically cannot have their output neutral lead grounded (if inverter neutral grounded and battery bank grounded--creates a dead short through the inverter). Typical TSW inverters can have ground referenced neutrals. (as always, see manual for installation instructions/warnings).

    In the end, except for price, TSW are a much better choice. Given that they are many times more expensive than MSW--it is a hard call sometimes.

    Sometimes, the option is to get a small TSW for electronics and a big / cheap MSW for non-critical larger gear.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: What is the difference between the two?

    Modified Sinewave (more accurate name would be modified squarewave) is made of just three voltage levels. The levels are -155 v, 0 v, and +155 v. (for 120vac output).

    The three levels are roughly invoked for 1/3 of AC cycle. The r.m.s. voltage of the waveform equals 120vac. They produce a lot of high frequency noise due to the abrupt voltage transitions.

    A 5 kW MSW inverter that runs on 12 vdc is a bit of a joke as it would require about 500 amps from 12v battery at full rated power. Generally, 12v inverters should be limited to 1500 watts and below. 3kW and below for 24vdc inverters.

    True sinewave inverters use a high frequency pulse width modulated squarewave that is then filtered with an L-C output filter to produce a sinewave. Its peak voltage is 170 volts just like a normal 120vac r.m.s. grid voltage.

    True sinewave inverter have higher no load current drain from battery due to the high frequency chopping of their output MOSFET's and output filter. Typical is 30 to 50 watts depending on inverter power rating. MSW no load current is low amounting to only a few watts.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: What is the difference between the two?

    RCinFla is correct,

    I went and took a quick look at Magnum's inverters (because they offer similar models in both MSW and TSW inverters) and the TSW has ~2.5 +/- more "fixed/tare" losses (at zero watt load) vs the MSW. Less than 12 watts for MSW vs 25-30 watts for a TSW 2k-3k watt inverter.

    In the end, look at your needs (load wise, day/night/optional/must have/etc.) and what will best power them.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • VanDeusen
    VanDeusen Solar Expert Posts: 129 ✭✭✭✭✭
    Re: What is the difference between the two?

    I do know many people tell me that 5k is too much so yesterday I switched it to my emergency backup inverter that is a msw 2500/5000 peak and was surprised that it wouldnt even run the washing machine which the 5000 does nicely.

    AT ONE TIME I can run the following:

    fridge (running of course)
    washing machine (washing a load)
    and my computer and as many lights as I want to run.

    I DO have AC but I have that on the electric companies service as I discovered that my 110 ac will run for about 4 hours before bringing the batteries lower then I want. (I only have 4 6v 395 amphr) running at 12v so tech. have 2 12v batteries. YES, I know that I am about 14 batteries short and am working on it as $$ allows but I wouldnt be able to use half of that above on a 2500 inverter. So, it seems that for my 4 floor household the 5000 watt inverter is the way to go.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: What is the difference between the two?

    If you want to operate that many loads at one time--Yes, you may need the 5KW inverter.

    However, you can have other issues too--Low battery voltage (too small of battery bank) / voltage drop from harness wiring... Although, your 5KW inverter worked (?)--So it would seem that those should not be issues.

    The other issue may be that motors can draw about 20% more power from a MSW inverter--So, some of your loads may be drawing more Watts (or Volt*Amps) than you expected too.

    If I recall correctly--we (or at least I) were concerned about your home's overall power consumption was pretty large for an off-grid system. It is pretty easy (and cheap) to get large inverters--Large capacity battery banks and solar arrays are, on the other-hand, quite expensive and can be difficult to wire.

    -Bill

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: What is the difference between the two?
    VanDeusen wrote: »
    I do know many people tell me that 5k is too much so yesterday I switched it to my emergency backup inverter that is a msw 2500/5000 peak and was surprised that it wouldnt even run the washing machine which the 5000 does nicely.

    I'm not surprised. It has nothing to do with the Wattage and everything to do with the waveform. Washing machines have a (usually) 1/3 HP AC induction motor - the very type of device that does not function well on MSW (Modified Sine Wave, Modified Square Wave, Multiple Square Wave - whatever it is we decide to call it). A refrigerator's 1/4 HP version of the same motor probably would run, as it is less demanding and a 'small frame' type which are not as adversely affected by MSW. How should I explain it? The MSW waveform does not create the right shape electromagnetic field in the motor? Power Factor incompatibility? Apparent low Voltage to the device? However you want to look at it, it's a no-go.
    AT ONE TIME I can run the following:

    fridge (running of course)
    washing machine (washing a load)
    and my computer and as many lights as I want to run.

    I DO have AC but I have that on the electric companies service as I discovered that my 110 ac will run for about 4 hours before bringing the batteries lower then I want. (I only have 4 6v 395 amphr) running at 12v so tech. have 2 12v batteries. YES, I know that I am about 14 batteries short and am working on it as $$ allows but I wouldnt be able to use half of that above on a 2500 inverter. So, it seems that for my 4 floor household the 5000 watt inverter is the way to go.

    I can do all that (and more) with my 3.6 W Outback sine wave inverter and 320 Amp/hrs of batteries. Another problem you may encounter is with your 12 V system trying to supply such Wattage: the current levels are high and the DC Voltage drop could be too much; the inverter may shut down as a result. A 12V system runs from 10.5V to 14.4V (or perhaps a bit higher). The more load, the lower the Voltage goes until it hits that shut-down point. This is why it is recommended that for heavy loads you go up in Voltage. One of the reasons anyway.
  • VanDeusen
    VanDeusen Solar Expert Posts: 129 ✭✭✭✭✭
    Re: What is the difference between the two?

    well with the current system it seams like my only problem is the fact that I dont have enough batteries OR panels. Like I said earlier, I can run everything fine, at night I have to use a battery charger to help out but even a 40amp xantrex only needs to be ran at about 20% power. When I wake up in the morning it tells me the batteries are fully charged.

    Considering the utilities to this house run 700 per month and with the setup I have now (minus air conditioning) my new utility bill is 30-50 I say that I am on the right track.

    It sems that IF (IF) I had more batteries I could illiminate the need for the battery charger. I do know that with MORE batteries= more panels. and that is what I am working on.

    The other day we had a storm come thru and it knocked out the transformer and the town was in the dark.. OH wait I WASNT IN THE DARK...LOL And that was like a turn on for me.. HA HA I thought as I watched tv. In fact, just to be hateful.... I turnhed on ALL the lights on ALL 4 floors at to say NA NA NA NA NA I have power and you dont....LOL Yes, that was probablyt rude of me but just couldnt help myself.

    I think that with 4 more panels and 4 more batteries I could probably turn off the utility company all the way except for the fact of air.

    Which brings to mind has anyone seen those solar powered AC'S? what do you think of them?
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: What is the difference between the two?
    VanDeusen wrote: »
    well with the current system it seams like my only problem is the fact that I dont have enough batteries OR panels. Like I said earlier, I can run everything fine, at night I have to use a battery charger to help out but even a 40amp xantrex only needs to be ran at about 20% power. When I wake up in the morning it tells me the batteries are fully charged. .........


    So, are you using grid to charge the batteries now, or just solar ? I'm concerned that you may have too much battery, and not enough solar (which is why you have to charge with 8A (20% of a 40A charger) to keep up at night.
    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 ,

  • VanDeusen
    VanDeusen Solar Expert Posts: 129 ✭✭✭✭✭
    Re: What is the difference between the two?
    mike90045 wrote: »
    So, are you using grid to charge the batteries now, or just solar ? I'm concerned that you may have too much battery, and not enough solar (which is why you have to charge with 8A (20% of a 40A charger) to keep up at night.

    the system is off grid. Solar in the day, Grid at nite (xantrex) I DO still have electricity here and I have the air cond. and the xantrex hooked up. I think i dont have enough batteries. So I use the xantrex at nite to help out the system so the volts dont drop too much. Without it by morning the batteries will be at 11.8v and I try to keep it above 12.0v so that I dont cycle the batteries. If I removed a battery (that would be 2-6v batteries) I think it would drop even faster.

    Correct on the not enough panels. I do need more so in the meantime I use the xantrex as the batteries (which you have to buy 2 at a time) cost me 500 each time and money is scarce.