Pure Sine Wave, or Not ?

[marshmat]

If you have to ask whether you should be getting a mod-sine or a true-sine, you should probably be looking for a true-sine inverter.

However, there are always a few engineers in the crowd who happen to be cheapskates. They'll recognize that a low pass filter circuit using a few very cheap passive components is all that's needed to turn the mod-sine into a reasonable approximation of a true sine wave. Since this involves designing and building your own 120 V circuitry, it won't have certain safety approvals that insurers like to see, and is definitely Not For Amateur Use.

[NotQuiteLost]

Originally Posted by daddle

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....

Oh yeah, it's an oldie. Little, puny emerson 21" TV/DVD combo (bought back when such things cost a few hundred bucks). I've got a 61" RPTV that I'm trying to figure out how I can fit into the boat. I've got two ideas, but both require varying levels of remodel to achieve.

Other than that, there's this absolutely GORGEOUS, perfect Panasonic plasma that's $1k on Amazon. I'm really drooling, being a videophile/video game freak. There are five places I could put that one in my salon.

[mikereed100]

Originally Posted by NotQuiteLost

there's this absolutely GORGEOUS, perfect Panasonic plasma that's $1k on Amazon. I'm really drooling, being a videophile/video game freak. There are five places I could put that one in my salon.

Sounds like you will need 5 of them!

[capn_billl]

Originally Posted by Blue Stocking

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

I dont know where you are at, but not true in the USA. Power is strictly regulated at 60 hertz created by a grid massive generators that spin at precisely controlled speeds it is impossible for the frequency to vary and would cause catastrophic failure of the power grid if it did. It is literally accurate enough to run a clock, and most AC plug in clocks merely use a small synchronous motor with a 60 to 1 reducing gear to keep the time, and will only lose a few seconds a year. Voltage is a lot less critical and depends on the impedance ratio between the final transformer and the load, but is usually 117-119 Volts RMS except in remote areas or places and times the local service is under peak loads. Noise is miniscule due to miles of inductive filtering. The transformer on the input of most devices filters the rest. Modified sine waves are more like modified square waves. So you lose a significant portion (18-30%) of the power to noise. Only a few cheap low powered devices work with it. Motors work but consume more power and may not be able to start. Non computing devices will probably work, but cpu's can be confused by even small amounts of noise on incoming power. My personal experience; I tried several brands of MSW inverters before chucking them all in the trash and buying a pure sine wave inverter, (Xantrex 1KW). I have had no trouble ever since. It even runs the fridge smoothly and quietly, while simultaneously running the computer and the TV/DVD. The MSW 2.5KW would choke if I even ran 2 of the three and the fridge sounded like is was going to come apart and the compressor ran very hot and often stalled popping the breaker. And the TV had wavy lines, etc...Buy what you want, but good luck selling the used MSW inverter after you are tired of dealing with it.

[denverd0n]

Originally Posted by capn_billl

Voltage is a lot less critical and depends on the impedance ratio between the final transformer and the load, but is usually 117-119 Volts RMS except in remote areas or places and times the local service is under peak loads.

You must mean "remote" places like Raleigh, NC; Denver, CO; and Tampa, FL. I've lived in all of these places, and have measured plug voltage in all of them. And in all of them the voltage fluctuated regularly and constantly between 110-120 volts. Sometimes spending hours at a time in the 110-115 range. At less frequent times the voltage (in all of these places) would dip below 110 or go above 120. The worst was Raleigh, NC where I saw voltages as low as 105, or as high as 125, that lasted for more than a half an hour.

[AnchorageGuy]

We have run modified sine wave inverters for many, many years with no ill affects to tools, electronics, computers or anything else, but that is just our experience. Having said that, a pure or true sine wave inverter will give you power matching what you get off the power grid when plugged in. The price difference between the two is so small now that it makes sense to just go with the true sine wave. Some digital electronics and digital readouts on appliances are not happy with a modified sine wave but they will work. Some rechargeable batteries and battery chargers should not be used on modified sine wave inverters. Chuck