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Efficiency and maximum power transfer
On Jun 7, 7:14Â*pm, Owen Duffy wrote:
wrote : On Jun 7, 12:43�am, Owen Duffy wrote: wrote innews:73353273-a079-499c-89df-c11975b37c78@z66g200 0hsc.googlegroups.com: ... The maximum power theorem gives conditions where power in the load, is equal to internal power in the generator. �Not always a good ide a. �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. Actually, the AC power distribution system from alternator down has a manged substantial equivalent source impedance. The source impedance serves to limit fault currents, which reduces the demands on protection devices. Sure, the network is not operated under Jacobi MPT conditions, but neither does it have near zero source impedance. Owen Not really sure I agree. Â*A multi-megawatt 60HZ generator by necessity has near zero source impedance. Â*The ones I am familar with require forced air cooling on their output buses. Â*If you are pumping out Mega- watts, then any non -zero source impedance results in serious heat. I^2R. Gary N4AST Gary, you use the terms impedance and resistant as if they were equivalent. Alternators have a designed value of leakage reactance, and they also have resistance. The combination make the equivalent source impedance, and it is sufficient to limit fault current to something typically in the range of 20 to 50 times the rated output current. Transmission lines and transformers in the transmission and distribution networks are usually designed in the same way. It is not zero, and it is not purely resistive. Most supply authorities would not allow you to connect a capacitive load (a leading PF load), so another concept, conjugate matching (in the Jacobit MPT sense) is also not practiced. Understanding the electricity network does not really give an insight into a typical ham radio transmitter, they do not share the same design objectives. Owen- Hide quoted text - - Show quoted text - We are obviously talking about two different things, that as you say have little to do with a Ham Radio transmitter. Gary N4AST |
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