Florida Shooters Network

A modified sine wave is usually unfiltered and noisy...I’ve seen the outputs of these inverter types on oscilloscopes. Some are so bad as to meet technical specs for sawtooth waveforms.
Never heard of PWM-type RF inverters but PWM (pulse-width modulated) motors are usually driven by a servo controller with feedback loops. They usually use 3-phase inputs that precisely regulate RPMs. The ones I have experience working with are 3-phase, 400Hz azimuth drive motors for radar antenna assemblies. Very expensive.
As stated in the previous post, inverters with a “clean” sine wave usually work best for supplying AC motors and other sensitive electrical components such as refrigeration compressors.
Most modern commercial electronic devices incorporate filters on the front end of their inputs that protect the downstream components/circuitry from “dirty” AC source power.

I always thought the modified sine wave was just a multi-stepped waveform.

Dave, you could be right on that. I’ve never worked with that type.
This is the older style function generator we have at work:

There are newer models out there but the one we have still works, so we keep on using it.

BerettaRacer wrote: ↑Fri Jan 04, 2019 1:02 pm 3000W @ 12V is a serious 250 Amps!! Your alternator is maybe putting out 100 A for short duration, more like 50 A continuous. You start pulling 250 A on a regular basis and your going to have some equipment, as in battery, alternator & wiring doing some complaining, and failures! System is just not designed to more that kind of amps on regular basis.

Might want to check that math again. 3000 watt DC to AC innverter will put out 25 peak amps and 16 continous. Depending on the inverter it will draw about 5% more amphs from the source but thats about it. At a reasonable draw a 800 amp battery will run one long enough for a hurricane to pass and you can get your generator hooked up. I've kind of done this, several times over the last 25 years.

Thanks for all of the info.

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TACC wrote:Thanks for all of the info.

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Dave P wrote: ↑Sat Jan 05, 2019 8:26 am I always thought the modified sine wave was just a multi-stepped waveform.

"Modified Sine Wave" is a marketing label, not a technical description. It means whatever the marketeer wants it to mean, but you don't get to find out exactly what the marketeer wanted it to mean unless you get him called to the witness stand in a civil suit over false advertising.

lilwoody wrote: ↑Sun Jan 06, 2019 6:33 pm

BerettaRacer wrote: ↑Fri Jan 04, 2019 1:02 pm 3000W @ 12V is a serious 250 Amps!! Your alternator is maybe putting out 100 A for short duration, more like 50 A continuous. You start pulling 250 A on a regular basis and your going to have some equipment, as in battery, alternator & wiring doing some complaining, and failures! System is just not designed to more that kind of amps on regular basis.

Might want to check that math again. 3000 watt DC to AC innverter will put out 25 peak amps and 16 continous. Depending on the inverter it will draw about 5% more amphs from the source but thats about it. At a reasonable draw a 800 amp battery will run one long enough for a hurricane to pass and you can get your generator hooked up. I've kind of done this, several times over the last 25 years.

Sorry, your wrong. Might want to check that math again. Look at the post below yours.
3000W output divided by 12V = 250A input

Here's a link to a inverter calculator to those that don't understand ohms law.

https://www.batterystuff.com/kb/tools/a ... erter.html

Also the cold crank amp rating and the amp hour ratings are two different animals.
Most 8D batteries are only rated at 250 amp hours. Once you reach low 12's, high 11 volt ratings on battery draw downs, inverters shut down.

Buy a suitcase gen set. Gas is cheap.