The reason they call it a modified sine wave is that it is a square wave with the same peak and RMS voltages as a sine wave. Since the RMS value of a (bipolar) square wave is equal to its peak value, it has to include parts at zero or a lower voltage. Some inverters use additional voltage steps to more closely approximate a sine wave but I think they are less common now that true sine outputs have become more economical.
I do not know why Don Lancaster's Magic Sinewave idea is not used more widely. Does it have patent issues? Maybe it is not economical compared to a true sine output. In the past I have used the predicable sine average responding and RMS values of a square wave to calibrate its peak-to-peak value for use as a calibration source. This is useful for calibrating analog oscilloscopes if you have an uncalibrated source but a good sine average responding or RMS (or both for a sanity check) AC voltmeter. On Mon, 25 Jul 2016 10:29:02 -0700, you wrote: >Hi Chris: > >The APC RS1500 uses what they call modified sine wave, but I call modified >square wave, i.e. it's a square wave with a >couple of parts that are at zero volts. >Don Lancaster promoted "Magic Sinewaves" where a pulse modulated waveform >drives an H-bridge. The leading and trailing >edges are determined using the idea of FFT so that all the harmonics up to >some number (typically 9 to thirty something) >are zero. There were also 3-phase versions. But he no longer sells any >hardware. > >PS I'm looking for a source of 3-phase 400 Hz 115 VAC to power a North Finding >Gryo. >http://www.prc68.com/I/WildARK2.html _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
