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Re: NST power rating -- another perspective



Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net> 



 > Original poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br>
 >
 > To see that the general expression doesn't work, try to compute the
 > power when Vsec(s)=V/s, a step function (or DC), and L=0:
 > PL=(V/s)^2*RL/(R+RL)^2
 > The inverse Laplace transform of this is a ramp, not a constant as it
 > should be.
 > Note that to obtain the correct value making s=jw you have to consider
 > Vsec as a constant, a phasor, not the Laplace transform of Vsec(s)
 > when s=jw. A product of Laplace transforms is a convolution in time,
 > not a product. Power is a nonlinear function of the voltage, and can't
 > be calculated directly from these transforms, although, as you observed,
 > some simple tricks give the correct answers.
 >
 > Antonio Carlos M. de Queiroz


The more I think about what you say, the more I think that my thinking may
only be correct at a constant frequency.  This is how I use these
transforms.

Gerry R.
Ft Collins, CO