MSW Interter

[Pete Masterson]

Most electronics covert 120 vac to 5 (or so) vdc current. The problem is less a matter of the electronics as it is the ability of the power supply to deal with the conversion.

The exception is electronics that have small electric motors -- for example a computer printer. Most work very poorly, if at all, with modified sine wave inverters.

I've used Uninterruptible Power Supplies with my multitude of computers for years. These are, essentially a small 12 vdc battery and an inverter. The inverters are all modified sine wave type. Even though I have UPS with sufficient power to handle a laser printer, no laser printer I've tried has ever worked with the UPS.

True analog sine wave power is a smooth cycle of the AC power. A graph of the wave shows simple curved lines. The power "swings" from side to side in a smooth transition.

A square wave (as displayed on an oscilloscope), digitally created, AC power is "instantaneously" switched in the alternating flow of AC. Electric motors simply won't run with this kind of power and many appliances that do run, might vibrate or buzz. Lights will work, but might buzz or even flicker (at 60 cycles per second). Square wave digital power is rarely used.

Modified sine wave inverters perform the switching in 3 or 4 steps making a blocky, stair-step wave on an oscilloscope. Most appliances can deal with this well enough. Most electric motors will run, though inefficiently, generating more heat (and drawing more electricity than normal).

"True" sine wave inverters aren't that different from modified sine wave, but the steps are 'chopped up' more finely -- in dozens or even hundreds of steps -- to more closely match the analog AC wave form. While there is a bumpiness to the wave, the steps are so small that they are treated almost the same as the analog wave form. For example, electric motors will operate efficiently with littledetectibledifference from a "real" analog sine wave AC power as received from a central power station or generator.

Pete Masterson

'95 Blue Bird Wanderlodge WBDA 42

El Sobrante CA

"aeonix1@mac.com"

Photos:

http://picasaweb.google.com/Bluebirdzoom/PeteMasterson#

On May 11, 2009, at 2:25 PM, freewill2008 wrote:

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Lots of times a modified square wave inverter will run electronics fine, but it depends on the particular device being powered so its not always predictable.

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