Efficiency and maximum power transfer
The maximum power theorem gives conditions where power in the load, is
equal to internal power in the generator. Not always a good idea. A
50HZ generator capable of Megawatts of power would dissiapate 1/2 in
the generator and 1/2 in our houses if they designed them to conform
to the MPT. The 50HZ generators would melt. Utilities design their
Generators to have nearly 0.0 ohms internal impedance.
Good question.
Gary N4AST
Whay you write is perfectly true.
To maximize efficiency, the ratio between load resistance and generator
resistance must be as high as possible. That is the reason why the internal
resistance of the Megawatts generator you took as an example is always made
extremely low (very little power is so dissipated within the generator).
Those generators however do not operate in the maximum power transfer condition
(generator resistance = load resistance). As a matter of fact one cannot
decrease the load resistance below a certain threshold because of the generator
power delivery limitations.
In other words the generator can deliver the maximun power it is able to
deliver, but not under maximum power transfer conditions. Never mind, what is
important is that efficiency is good!
73
Tony I0JX - Rome, Italy
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