On Mon, 14 Apr 2008 16:54:47 GMT
Cecil Moore wrote:

Roger Sparks wrote:
While it can be argued that the ideal voltage source would
have zero internal resistance, that argument does not address
the fact that power flowing in the reverse direction (into the
source, against the source supplied voltage) delivers power
into the source.

I thought I had already addressed that topic when I added the
one-wavelength of transmission line to the example in between
the source and source resistance.


I thought the addition of a one wavelength transmission line did not address the issue, and only added more reflections. We still need a reason to assume that a voltage source should *not* absorb power.

But here's an example that may allow better tracking
of the energy flow. Let's modify my Part 1, Fig. 1-1
to add a 50 ohm circulator and load to the ground
leg of the source. Everything else remains the same.

Gnd--1---2---Vs---Rs-----45 deg 50 ohm----------RL
\ /
3
|
50 ohms
|
GND

How much power is dissipated in the circulator
resistor?

How much power does the source have to supply to
maintain 50 watts of forward power on the transmission
line?

Does this example answer your questions?
--
73, Cecil http://www.w5dxp.com

No, I'm sorry but no. I offered the examples of two real sources that will absorb power when the returning voltage exceeds the output voltage (a battery and a generator turned into a motor). I think that we must allow our voltage source to have that same real property.

I do understand that when we allow the source to receive power, then we need to address source impedance. If we assign a single impedance, then we expect reflections from the source. The simple solution that I propose is to add a source property of absorbing all reflections. This can be accomplished in the real world by making the transmission so long that reflections never return from the source over any reasonable time, or by making the tranmission line sufficiently lossy to absorb reflections. Your example uses the first method.

Does the idea of source receiving power run counter to what you were planning to write in Parts 2 and 3? I am trying to understand why you have such great reluctance to accept that the source could receive power for part of a cycle, especially when it could easily bring the instantaneous power and energy calculations into balance.
--
73, Roger, W7WKB