Power Inverter

"Modified sine wave" means 'square', or worse. Some electronic gear will be wrecked by the power spikes that some of these produce. Somw gear won't run on them at all.
Personally, pure sine wave only, for my money.

Cheers,
Peter

I agree with Peter. The term "Modified Sine Wave" should never have been coined. It is actually Modified Square Wave and does not approximate to a sine wave at all. It merely has approximately the same peak and RMS characteristics as an equivalent sine wave (same as mains power) but that does not mean it will satisfactorily supply appliances that require sine wave power. Unless you know your appliances' requirements then you use one at your peril.

There may be good reason why Oldbaz (above) uses one with success on his 3-way fridges. These fridges have only a heater element to be powered and this will work satisfactorily on modified sine wave, or even on square wave for that matter. The fact that his fridges work better than when on 12 volt simply reveals that the inverter is supplying more power in that mode, not that modified sine wave is better all-round power.

Like most things electrical, there is a lot more to it than the simplistic reasoning that some people employ.

Navara, try Googling "modified sine wave" and you will find many responses that may overwhelm you, but most will warn you of the perils of square and modified sine wave inverters. Unless you are certain that "Modified Sine Wave" will suit your purposes then spend a bit more and purchase a Sine Wave inverter. It could be good insurance.

The same comments as above apply to portable generators in regard to selecting their output waveform.

Just how close to pure sign wave is your pure sign wave inverter, is the question.
Pure sine wave and modified sine wave inverter outputs are both modified sine waves.
But one is closer to pure sine wave than the other.

Regards Dennis

Hi Dennis,

Well I doubt that any inverter marketed as "Pure Sine Wave" is anywhere near "pure" but possibly most on the market today are near enough for practical purposes. I just wish they were marketed as simply "Sine Wave" rather than "Pure".

I have had the oscilloscope on mine and it is not too bad. Changes a bit with varying loads but no nasty spikes or harmonics. Looked a bit like a sine wave with shoulder pads! The load type (inductive, capacitive or resistive) also affects the waveform but not markedly. Suits my purposes.

I have no supporting evidence, but knowing the necessary strategies required to produce an approximated sine waveform, I would expect that the waveform "quality" would be somewhat linked to the purchase price. In other words, you probably get what you pay for. That also goes for the load devices powered by the inverter......... the more rudimentary switch-mode power supplies are likely to be less tolerant of the quality of the waveform supplying them. No proof, just a hunch, but there is bound to be exceptions and I have seen some!

And yes, I agree.......... "one is closer to pure sine wave than the other".

Yep the quoted “pure sine wave” ones are close enough for what we want, though I don’t have one.
I have a “modified one” that has run the following without killing them, a laptop’s power supply, an electrical drill, a small TV, a mobile telephone battery charger and NiMh battery charger.
I would try it on other equipment but it is only a 300 watt unit.
I would plug anything into it, as a test, if the gear I was trialling was under warranty.
DON’T TRY THIS AT HOME it’s not a recommendation – I don’t want people complaining that their gear went up in smoke on my say so.
Regards Dennis

Forgot to mention - The supplier of my satellite disk agreed that it wouldn't hurt his decoder box (after I told him I'd tried it).
Regards Dennis

Good advice Mainey.

I went the inverter path on the advice of my BIL, an electrician, who predicted improved performance of my 3 ways on 240v, & he was correct. Your assertion
that over 300w requires a second battery is not accurate. I have only the cranking battery & this is more than adequate to power the inverter & all other
devices while driving. Stationary power is supplied by a Honda 20i genny or gas
or mains 240v. The solar option is expensive, & so is the extra battery under the
bonnet. My system is more flexible, gives power day or night, utilises existing 240
appliances & tools, & cost a fraction of an equivalent 12v system....oldbaz.