🚀 go-pugleaf

In article <1992Sep14.210900.1@acad2.alaska.edu> aslt@acad2.alaska.edu writes:

>Many inverters use square waveforms rather than sinusiodal waveforms. 
>Intuitively, though, it seems that significantly less energy will be 
>transferred from the primary to the secondary of the transformer using 
>square waves (input changes at discrete places in the waveform) than 
>would be transferred using sinusoidal waveforms (input continuously changing)
>What am I missing?

	First, a square wave is simply a lot of different frequencies
all lumped together; the efficiency of the transformer would have
to be less at high frequencies for the square wave drive to
have some disadvantage over the sine-wave drive.  Some sources of
energy loss ARE worse at high frequency (eddy current losses
in the transformer iron) while some are improved (saturation
losses).

	More to the point, the DRIVING  circuit is typically running
off a DC source, and can operate with nearly zero loss ONLY when
switching (which produces... square waves).  There are some tricks
to generating sinusoids, but they require extra inductors or many
taps on the transformer, and are not employed casually (nor cheaply).


>Along the same lines, presumably the outputs of inverters are square waves
>rather than sinusoids (I'm speculating, I don't know).  It seems you could 
>do some serious damage to the motors in some devices, drills, margarita 
>blenders, refrigerators, freezers, and such.  Any comments?

	Probably not; the series inductance in a motor results in
the higher frequency components of the square wave being...ignored.
If you fed an AC motor with DC, it'd damage it.  Feeding it with
too high a frequency, you'd simply lose torque (and the motor would
not draw current).  The worst case would be if it made the motor
respond acoustically (instead of a comforting hum, your refrigerator
would make an annoying BUZZZZZZ).

	John Whitmore