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Old 04-05-2011, 19:35   #16
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Re: True (Pure) Sine Inverter vs Modified Sine Inverter

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Originally Posted by David M View Post
It's actually a modified square wave. Why would anyone want to modify a sine wave to something less useful?
Because the electronics required to generate a modified sine wave, probably more correctly called a stepped inverting square wave, from a DC source are way cheaper that the electronics to generate a nice smooth sine wave. The number of steps simulating the sine wave depends on the vendor. The really cheap ones only have one. Nobody wants to actually modify a sine wave, the want to generate a wave close enough to a sine wave in a way that will run some AC electrical devices. What's close enough for some devices is not close enough for some others.
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Old 05-05-2011, 00:04   #17
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Re: True (Pure) Sine Inverter vs Modified Sine Inverter

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Because the electronics required to generate a modified sine wave, probably more correctly called a stepped inverting square wave, from a DC source are way cheaper that the electronics to generate a nice smooth sine wave. The number of steps simulating the sine wave depends on the vendor. The really cheap ones only have one. Nobody wants to actually modify a sine wave, the want to generate a wave close enough to a sine wave in a way that will run some AC electrical devices. What's close enough for some devices is not close enough for some others.
Bill, I think he was having a laugh!

BTW, if you can find one, the old APS UPS units have pure sine wave inverters in them. They are often tossed when their batteries die.

Of course you need to be very confident in your electrical skills to mess about with it.
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Old 05-05-2011, 03:53   #18
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Re: True (Pure) Sin Inverter vs Modified Sin Inverter

I would go for a pure sine wave.
Inverters tend to be more efficient at close to their maximum output , so go for a unit as small as you can get away with. Try to run as much as possible from 12v. On my boat the only thing that the inverter is used for is the stick mixer for the kitchen. Occasionally I use it for charging drill or camera batteries, but I can charge these from 12v, but it’s a bit more hassle.

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Originally Posted by Intentional Drifter View Post
For example, common inverter loads look like (assuming 12 volt bank converted to 120 volt AC):

• Blow dryers (a 1200 watt blow dryer run on the inverter uses 100 amps! Use it for 15 minutes and you have burned over 25 Amp/hours from the battery bank.)
• Microwave (at 1000 watts, it uses 83 amps through the inverter, or 21 Amp/hours for 15 minutes.)
• Ice maker (uses 23 amps through the inverter, so running it for 4 hours on the inverter will consume 100 Amp/hours from the battery bank.)
• Salon TV (at 100 watts, uses 8.3 amps through the inverter, or 25 Amp/hours to watch for three hours)
• PC (at 65 watts, uses 5.4 amps through the inverter, or 17 Amp/hours for that 3 hour movie)

Oink! Oink! Lots of common appliances are real energy hogs.

ID
The Peukert's Formula will mean that the effective draw from the batteries will be much larger than these figures suggest(although they are mathematically correct). Almost 50% more at 100 amps than these numbers show.

Here is a calculator for the effect.
Notes on Batteries
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Old 05-05-2011, 07:16   #19
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Re: True (Pure) Sine Inverter vs Modified Sine Inverter

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Originally Posted by David M View Post
It's actually a modified square wave. Why would anyone want to modify a sine wave to something less useful?

YEAH! I wonder!! Why....??

LOL
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Old 05-05-2011, 07:19   #20
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Re: True (Pure) Sin Inverter vs Modified Sin Inverter

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Originally Posted by noelex 77 View Post
.........

The Peukert's Formula will mean that the effective draw from the batteries will be much larger than these figures suggest(although they are mathematically correct). Almost 50% more at 100 amps than these numbers show.

Here is a calculator for the effect.
Notes on Batteries
Thanks for the link..
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