I bought a 1000W pure sine wave inverter off ebay for $230. So far it appears to work quite well. From what I can test with a multimeter it appears to be true to the figures quoted (standby currrent 0.6 amps, low voltage alarm at 11V). But without a scope, is there a way to check if it is really a pure sine wave unit?
Cheers, Michael
"Mickel"
** Get an *AC* plug pack that can deliver say 6 volts at 1 amp and plug it into the inverter.Connect the 6 volt output to a decent hi-fi speaker and listen to the sound.
A pure sine wave should be very deep and clean sounding.
..... Phil
**The term "pure sine wave" is a very rubbery one. The standard 240 Volt mains supply can be termed pure sine wave, since it has respectably low levels of distortion. To get any better than that, you will need to invest a couple of grand into a mains 'reconstructing' device. PS Audio and others make such devices. At HUGE cost. 230 Bucks is unlikely to buy you a device with less than around 10% THD.
Ask yourself why you need 'pure' sinewave. If the inverter is to be used for general purpose power for things like motors, lights, maybe a PC power supply source, it does not matter at all.
If you power some critical piece of equipment that relies on low harmonics in the supply line, like some transformer coupled low noise power supply, then it may not work very well.
I plugged an electric fan into a "modified sinewave" inverter, and not only did the motor produce a buzzing noise, but it was clear from the smell that the motor was overheating.
Sylvia.
To be expected. You used a "modified sinewave" inverter. the rec was for a "pure sinewave" inverter.
The approximate types are stages are a) crap wave, looks all most like squarewave b) "modified sinewave" has less steps than you have fingers and is over priced crap,
c) "unspecified", has far more steps than fingers. d) pure sinewave, aka should be smooth sine wave output.
Yes. I read Adrian's comment as indicating that it doesn't matter what form the wave takes for things like motors, etc., and that any inverter would do. My experience shows that that's certainly not the case for motors.
Maybe his intent was that it doesn't matter if the wave diverges a bit from a sinewave for the cases he identified. That's probably true.
Equipment that can't tolerate a moderate degree of harmonic distortion is likely to be more trouble that it's worth.
Sylvia.
In fact usually IS a simple square wave.
I real misnomer, what should be called a "modified square wave"! Is usually one positive and one negative step with an off period in between so that both the peak voltage as well as avearge voltage are now similar to those of a sine wave. Waveshape remains roughly square.
Unspecified can obviously be *anything* but most likely same as a)
Should be a LOT closer than a) or b). Simply check the full load THD specs if it's actually critical.
MrT.
Not in my experience. YMMV.
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