Can a True Sine Wave DC inverter .....

Umm, how else would a washing maschine, a lathe, a tile saw and so forth be able to run in an off-grid solar home? I mean the good stuff, not the cheap stuff with brush motors.

Hint: Solar inverters are essentially tru sine devices as well.

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Regards, Joerg

http://www.analogconsultants.com/

OK, I didn't think of that.

Thanks

Sorry, the discussion of the Modified Sine wave inverter is what I wanted to ask about.

Can a Modified Sine wave inverter run an AC motor correctly ?

Google searching has said both ways, Yes and No.

Thanks again

hamilton

It depends. I guess you've heard that one before :-)

AC motors do not particularly like power with such high harmonic content. You are essentially feeding them a glorified alternating square wave. For example, the fans in our wood stove run on modified sine but slower than normal. Probably also with less efficiency which in the canse of a big pump could matter, and possibly cause motor damage if it's loaded pretty good.

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Regards, Joerg

http://www.analogconsultants.com/

.

I have operated a clothes washing machine. with a 1750 watt xantrex modified sine wave inverter.

Good as long as you have lots of battery power. If the batteries are not

100 percent, may not/will not start the motor during spin cycle.

Thanks

My goal is to run an air conditioning unit in my friends cabin in the mountains of Colorado.

Last year it was just too hot.

He has a generator, but at night it was too loud.

Getting the generator to charge the battery during the day and using batteries at night would make the whole trip easier.

Yes, I do like my creature comforts.

hamilton

I set up a Harbor Freight 1500 or 2000 watt inverter with a 12V battery = as a=20 backup for a friend's sump pump. It seemed to start and run fine. It was = a=20 lot better than what she had before, which was not much more than an=20 aquarium pump that was supposed to kick in when power was lost. I tested = the=20 regular sump pump with 5 gallons of water and it drained it in a minute = or=20 so. Probably would take a couple hours on the little "toy" pump.

Paul=20

It depends on both the inverter performance characteristics and the motor, of course.

Probably sort of like old car audio specs. Yeah, it LOOKS like a pure sine wave on a scope... UNLOADED.

The key is what the waveform looks like throughout its entire load window. If it can remain sinusoidal through that, the claim of "True sine wave" can be thought of as accurate. Very likely that some makers make the claim, but do not deliver at the upper end of their rated loading spectrum.

At some point in your life, you should just spend the money and get a good true sine wave inverter. The well known engineer Dianna Ross said "Ain't nothing like the real thing baby." I have a true sine for portable use and as my UPS.

Note you need to worry about VA rather than watts.

Not relevant to your case, but if you expect to run anything sensitive to EMI, I'd suggest getting a true sine with all the emissions ratings. That said, it is claimed the units that have no rating are fine, i.e. the manufacturer didn't want to pay for the certification testing.

You might want to check out Don Rowe.

They have commercial grade units for not much more than the schlock.

Their cables are a decent price, and made out of very flexible welding wire. Some inverters will spec that you use a fuse, which they sell as well.

you want to run air con at night?

get a ceiling fan, open some windows.

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If the air is dry during high temp periods consider an evaporative cooler. _Major_ reduction in power consumption. After we installed one I never want to miss it again.

Now that's where solar really would make sense.

Nah, real men don't need that. Clear some rocks and stones, plop down a horse blanket, take a few swigs out of the whiskey bottle, lay down, doze off :-)

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Regards, Joerg

http://www.analogconsultants.com/

Well, how many batteries will you have? If you are talking about one

12 V battery, it will run that AC for about 5 minutes!

Jon

Yes, that is something I need to understand better.

real men don't need a horse blanket!

Jamie

Well, yeah, but you have to take it off for the night anyhow and put it somewhere. Reduces the chance to find a rattlesnake in there the next morning.

--
Regards, Joerg

http://www.analogconsultants.com/

This sounds unlikely to work. Just look at the battery capacity and the draw of the AC.

I got a few Odyssey AGM that were used in eval for a battery based APU.

Given that they were abused a bit (hit with 100 amps), they couldn't go in the final product. [I'd hate to have to pay list for these AGMs.] Anyway, you are pretty much limiting to about 100AHr per battery. For the high power task you are looking at, you would probably want an inverter than does 24v or 48v input, or you will be having to swap batteries often.

You may want to do an internet search on "battery apu" since your task is well beyond the typical inverter task. Most of the battery APUs are for trucks, but there is an increasing military use of the technology.

Honestly, if he can afford it, I'd be tempted to just buy a quiet generator -- there are some out there specifically designed to be verrryyy quiet (e.g.,

Somewhat less expensively, perhaps you can build a large box for the generator with plenty of muffling (and ducted air intake/exhausts). It can do wonders as well if you can get it a bit away from the cabin proper...

I am stuck with the generator that is available.

That's why I am looking for a simpler (i.e. cheaper) solution then buying a new generator.

Thanks everyone for your insights in the project (problem).

hamilton

Good point about the inverter generators. I looked into this before going with the AGM solution. If the batteries weren't the right price, the inverter generator would be the cheaper solution, though my scheme is for camping and I hate messing with gas cans.

Incidentally, some suggest the Yahama version of these inverter generators is a better deal than Honda. All but their bottom of the line models have cast iron lined cylinder sleeves. [Check to be sure since I haven't look at this in a while.] Yamaha even has models that run on gasoline and LPG.