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Old 18-10-2010, 20:12   #1
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Pure Sine Wave, or Not ?

Having Googled pure and not so pure sine wave inverter characteristics I'm still no wiser.

Some pages give the impression that variable speed power tools will not be happy with anything but a pure sine wave power supply. I can imagine why that would be the case but then other "experts" make it sound like it depends on the tools and we'd probably be fine with an approximate sine wave supply.

Should we just plunk down the money for the pure sine wave inverter or is that likely to be a waste of money ?

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Old 18-10-2010, 20:23   #2
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Are you going to use variable speed line-powered (not battery) power tools at variable speeds? I suspect that it's true. There's your answer...

Of course I'd skip the whole power tool and line voltage boondoggle all together. 20,000 miles and haven't missed them yet.
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Old 18-10-2010, 21:45   #3
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Pure Sine Wave vs Modified Inversion

(From the above thread)

"I went pure sine. Main reasons: not a lot of price difference (at least for the Magnums I had narrowed it down to), PSW are less prone to annoying humming through electronics than MSW, and wanted to avoid having to upgrade later if/when our usage changes."

Seven months later and no issues with my Magnum pure sine wave charger/inverter. Highly recommended, esp. considering its price compared to Victron!
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Old 20-10-2010, 11:00   #4
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I might also add that if you use "A/C bricks" (those SMPS (Switch Mode Power Supplies) that come with laptops and about all portable electronics) they tend to run hotter with MSW (Modified Sine Wave).
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Old 20-10-2010, 11:35   #5
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Most appliances with a brain either protest or go on strike when introduced to modified wave.

I bought pure for peace of mind
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Old 20-10-2010, 12:42   #6
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I use the cheapest modified sine wave... the waves are square as bricks... and I have absolutly no problems at all. But I use a battery operated (variable speed) drill

Unless you are powering your own pacemaker then save the $2,000 and spend it on buying me beer.
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Old 20-10-2010, 13:16   #7
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The REAL reason to buy the sine wave inverter/charger

It makes no economic sense for cruising applications to buy only an inverter or only a charger, one should buy an inverter/charger/transfer switch all in one package, such as the Magnum product previously mentioned.

The REAL reason to get the sine unit is that it will be a harmonic-corrected switch-mode technology that extracts energy from the total sine wave when in the charger mode. To you this translates to being able to utilize a full 30 A from a 30A shore breaker when chaging heavily. Non harmonically "corrected" (used to be referred to as pfc, power-factor -corrected) chargers, like the usual MSW units greatly distort the input current waveform causing breaker heating with large amounts of apparent power. This can make a large difference when using small gen-sets to power the boat (and charger to charge batteries.

With the new switch-mode technology you get the best of all worlds.
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Old 20-10-2010, 14:40   #8
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I have been charging camera batteries and running my computer on a crappy little MSW inverter for years without a glitch. I know my computer should crash and my batteries should be fried but ignorance is bliss! That said, when when shopping for a bigger inverter for power tools I went with the Xantrex SW1000 because the things have gotten so much cheaper recently. I think I paid $237 including shipping.
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Old 20-10-2010, 14:51   #9
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When I was in nuclear power the reactor rods were controlled with a DC supplied current that was changed to a modified block sine wave. The reactor never melted down.....................wait what's that cloud over there rising into the sky!
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Old 20-10-2010, 15:17   #10
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Buy a pure. This issue has been beaten to death before. You will be much happier, so will everything running on it. The money you save buying a modified wont pay for the headache.
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Old 20-10-2010, 16:49   #11
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If you could see what your local grid is supplying, you wouldn't worry half so much about this.
57 to 63 Hz and 112 to 125 Vac.
Most modern equipment can deal with this, IMHO
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Old 20-10-2010, 17:03   #12
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A few years ago my "brick" type hand-held VHF stopped working immediately when plugged into a cheap modified sine unit. Would it have failed anyway? Don't know but it's the only time I've seen a "brick" type supply fail, in entire my life of 56 years. Just one data point. Now I only use pure sine inverters.

Why would they sell them for more if they weren't better?
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Old 20-10-2010, 18:14   #13
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Having owned both, and seen the MSW (modified sine wave) version gag on certain power products, I've gone to the pure sine and had no problems. Although I can't prove it, I think the noise generated is a bit less.
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Old 20-10-2010, 18:39   #14
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Quote:
Originally Posted by capt_douglas View Post
Having owned both, and seen the MSW (modified sine wave) version gag on certain power products, I've gone to the pure sine and had no problems. Although I can't prove it, I think the noise generated is a bit less.
All of my appliances make an audible buzzing sound on my MSW Heart (now Xantrex?) inverter. No equipment failures, but my laptops do run hotter at their power bricks, and my TV has gotten a little bit of that magnetic 'rainbow' effect which I can't attribute to anything else. Not saying for certain that's what did it, but it's all I can come up with.
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Old 20-10-2010, 20:13   #15
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The TV has a rainbow effect. Say you are not still watching an old fashioned TV?

You get the rainbow effect by changing the heading of the boat with regard to the earth's magnetic field AND perhaps your TV's degauss feature is busted. Sometimes inverters cannot supply the surge of power needed by a large tube degauss (Its that classic 'clunk' when a dinosaur TV is first turned on). Buy a LCD/LED TV....
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