Re: Voltage Converter
- From: Nobody <nobody@xxxxxxxxxxx>
- Date: Wed, 31 Oct 2007 03:19:17 +0000
On Tue, 30 Oct 2007 19:03:30 -0800, Robert Baer wrote:
A diode does not "double" the wattage.
In this case, a diode would "halve" the average wattage by giving you
"half" of the cycles.
Now, let's do a little Gedankenexperiment-- what would the power
dissipation of a "100W 120V" heater be if operated on 240VAC?
Best regards,
Spehro Pefhany
Well, if one had a square wave source, when the diode conducts, one
has 240V during that time, for P=E*E/R or four times the power then; the
other half of the time one has zero power; heating power is double as
claimed.
For a rectified/half sine wave, i do not know what the "RMS" would
be, but i would think it would be less than 240V.
The shape of the waveform doesn't matter, so long as the positive and
negative halves are symmetric.
If you apply 240V RMS to a 100W, 120V RMS resistive load, you get 400W. If
you halve the duty cycle with a diode, you get 200W.
Whether a square wave, sine wave, triangle wave, etc, halving the duty
cycle halves the power and thus reduces the RMS voltage by sqrt(2).
.
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