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CAPKELLY

Inverter Type

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I need to replace my Magnum inverter. It is a modified sine wave inverter  2000 W . What are the pros & cons of upgrading to a more expensive model type of the sine wave type?

In other words should I stick with modified sine inverter or go for a pure sine wave inverter?  I have all the usual rv electronics, tvs, computer, cell phone chargers, microwave convection oven.

 

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The price gap between a good MSW and Pure Sine Wave inverter has diminished quite a bit.

Particularly with the move to more sophisticated electronics, were I replacing one today, I would go with Pure Sine Wave.

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Thanks . So what is the difference of a msw - modified sine wave vs a sine wave inverter?  I was also thinking in the future of replacing refrigerator with a residential refrig. .does this make a difference which type inverter  I go with? Thanks for your help.

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Some residential refrigerators will run on MSW, many will not.  With the huge price difference years ago, there was a reason for MSW.  Today, I personally would strongly recommend a PSW inverter. 

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Inverter sine waves, Modified and Pure Link.

The red wave is pure and the Blue square cornered one is the modified version.

I cannot just attach images anymore because I have used up my allotted data.

So I hope this link clears up and or helps clear up the difference. 

https://www.google.com/imgres?imgurl=x-raw-image:///96c24e4d3934a383394786da90ae80669200dfdece0264b503cf3cb99cb22a57&imgrefurl=http://www.xantrex.com/documents/tech-doctor/universal/tech1-universal.pdf&h=230&w=225&tbnid=g6M0OU1OwpY5QM:&tbnh=160&tbnw=156&docid=c2v9GYxDH6kcmM&usg=__wb0eXU7_ykMSHHZnD10T3SXzJA8=&sa=X&sqi=2&ved=0ahUKEwjtksmikYnMAhWG1h4KHTX9AEkQ9QEIIDAA

Rich.

 

 

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Capkelly, I called GE before we purchased our residential fridge, they were no help in telling me if it would run on MSW or not. I called Xantrex for specs on the Inverter in our coach, they were a huge help. I was told there are different output quality levels of an MSW inverter also. Xantrex also explained that modern electronics do not like MSW, with that being said they advised me to either replace the MSW with PSW or select a more basic refrigerator without all of the electronics and gadgets. To keep my costs down we selected a energy efficient fridge with noting more than a knob inside to select for colder or warmer. I was told to compare the compressor sound when on shore power to inverter, if it louder while on inverter it will not last as long and the unit does not like the MSW inverter. I got lucky no sound difference (that I can tell) and works prefect. When the current invertor does wear out I will replace it with a PSW.

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As seen in the pictures that Rich linked to, the MSW "modified sine wave", changes the direct current to alternating current in a square looking pattern, noting the abrupt edge of the square wave, then levels out at the positive voltage for the correct interval that is necessary for 60 cycles per second, about 5 milliseconds, then abruptly goes down to the negative side of 120 volts for the same time period, then back up. Transistors are used to make this transition from positive to negative etc. When a generator produces electricity, the steady turning of the stator across the fields of the generator produces a curved pattern at the top of the pattern "positive", and again at the bottom "negative", and on and on for sixty times a second. PSW "pure sine wave" inverters use a much more complex series of transistors to imitate the same pattern as the generator. This makes them more costly to produce and also more complex while running. Most appliances of course will like the PSW more than the MSW. The PSW is more heat sensitive than MSW meaning that PSW actually requires more ventilation. With all this in mind, if I am using a MSW, and everything that is being powered to it is ok, then I would look for a fridge that runs ok on MSW. If in need of replacing the inverter anyway, I would certainly at todays prices, go to a PSW. But anything that is going to be used on an inverter, before purchase, look at the spec tag for the lowest amperage stated there, for heat, and battery longevity.

Kay

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CAPKELLY

I recently replaced my Freedom modified sine wave with a Magnum Pure sine wave and the best price I found was with RV Solar Electric (.com) from Doug.

The price includes the control unit which in my case was pure plug and play. The communication cable ends were the same and the holes for the control unit inside matched up perfectly.

 

Bill

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Capkelly, you are correct. I have gotten better information from here than any RV dealer/tech line I have ever reached out to so far. Its scary but most only want to hire what saves them money rather than what is the best person to handle their customers, which in the end makes them loose customers. Unfortunately the bean counters don't see it and don't care. Corporate today never sees the big picture only what's in front of them. 

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I was at an RV electrical seminar recently and the presenter said that a pure sine wave inverter is not pure, but rather has several more square wave steps to more closely approximate a pure sine wave.  Is that correct?

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24 minutes ago, dorgene said:

I was at an RV electrical seminar recently and the presenter said that a pure sine wave inverter is not pure, but rather has several more square wave steps to more closely approximate a pure sine wave.  Is that correct?

Yes, no way to completely electronically change dc to ac in its purest form, but as the cost and efficiency of transistors have improved, the PSW has improved to look more like a true generator sine wave. 

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On 4/9/2016 at 8:16 AM, CAPKELLY said:

I need to replace my Magnum inverter. It is a modified sine wave inverter  2000 W . What are the pros & cons of upgrading to a more expensive model type of the sine wave type?

In other words should I stick with modified sine inverter or go for a pure sine wave inverter?  I have all the usual rv electronics, tvs, computer, cell phone chargers, microwave convection oven.

 

I would upgrade to a pure sine sine wave. It is a much cleaner output, some electronics do not like the modified sine wave.

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I haven't done much research on the subject but in the early stages of PSW design, the efficiencies were somewhat lower which explains why some mfg want lot's of ventilation.  Heat is a killer in electronics.  Today's units may be significantly more efficient but I would look at that parameter as it will affect how long your batteries will last before requiring a recharge.  If doing a fridge changeout to residential, check with manufacture if they have tested using inverter source.  Also, some inverters may not be happy with certain brands of fridge.  Just like some marriages not compatible : >)

Bob in TX

BSEE/MSEE

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Bob, with more and more equipment and appliances going to microprocessor control systems, the need for a cleaner sine wave power is increasing and the newer SW inverters are getting better efficiency wise.

The difference in efficiency between modified and the newer sine wave units are now about 5% of each other. Not a real big issue when trying to compare battery life between the systems.

Rich.   

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