wrote in
:

....
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.

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

On Jun 7, 12:43�am, Owen Duffy wrote:
wrote :

...

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.

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. A multi-megawatt 60HZ generator by necessity
has near zero source impedance. The ones I am familar with require
forced air cooling on their output buses. If you are pumping out Mega-
watts, then any non -zero source impedance results in serious heat.
I^2R.
Gary N4AST

wrote in
:

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. A multi-megawatt 60HZ generator by necessity
has near zero source impedance. The ones I am familar with require
forced air cooling on their output buses. 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

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

Owen Duffy wrote:
"Most supply authorities would not allow you to connect a capacitive
load (a leading PF load),-----."

Incorrect. Overexcited synchronous machines are commonly used to correct
the power factor causing reduced line current and lower power loss on
the a-c power transmission line.

Best regards, Richard Harrison, KB5WZI

(Richard Harrison) wrote in
:

Owen Duffy wrote:
"Most supply authorities would not allow you to connect a capacitive
load (a leading PF load),-----."

Incorrect. Overexcited synchronous machines are commonly used to
correct the power factor causing reduced line current and lower power
loss on the a-c power transmission line.

In this part of the world, connection of an overall leading PF load
usually requires approval of the supply authority. Most electricians
would be aware of the restriction.

The reason being is that it can cause an increase in supply voltage
beyond spec in the local area.

Yes, large factories for example may use static or rotary power factor
correction to improve their PF for tariff reaons, but if an installation
reaches an overall leading PF it usually breaches rules in this part of
the world, and commonly permission is required to attach individual
'devices' with capability for leading PF. Some tariffs are based on
maximum demand, and often maximum apparent power (ie VA), not maxiumum
real power (ie W), hence the economic interest in PF correction.

Today, active static power factor correction that can dynamically track
a varying load at varying PF is a lot more attractive than rotating
machines.


Owen