AC mains input impedance

"Scott Ronald"

** Why not just measure it ??

Use say a kettle that draws a known current - 12 or 15 amps.

Monitor the AC voltage on a DMM when it is connected.

Use ohm law.

...... Phil

North American AC mains? Or does this vary

It is dependant upon the load you are using. It is the voltage drop/load Current.

Usually you will see the UL required mains impedance on the device label. This is the maximum Impedance require for proper operation.

Cheers

"Martin Riddle" "Scott Ronald"

** Nonsense.

Line Z is a parameter or the ACsupply and hence is independent of the load.

** Good, basic link.

** Huh ??

On what planet is the usual ?

....... Phil

Do you mean the line's behavior at 60Hz, or are you trying to use it for power line communication or something?

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Scott Ronald wrote in news:3Enyj.31278$pM4.13791 @pd7urf1no:

Totally idiodic!

What possible reason is there to even ask such a stupid question?!?

For anything you can possibly hook up to it, it is essentially zero....

"me the ego tripper "

** It ain't stupid at all - f****it. ** Not one bit true.

....... Phil

"Phil Allison" wrote in news:62vhg3F23nou8U1 @mid.individual.net:

ok, what reason?

how not?

do more than gas. (that is what I'm doing here (no cooping a squat on my territory))...

"me the ego tripper "

** Many reasons exist to know the impedance of power source.

If YOU cannot imagine even one - it is because

YOU are a TERMINAL FUCKWIT .

** It ain't zero.

It has a significant effect on the PSUs of many high current draw devices.

..... Phil

"Phil Allison" wrote in news: snipped-for-privacy@mid.individual.net:

You are a total assbag. There is no reason to care about the impedance of mains source. You use best/worse case voltage in any design.

No, see above, assbag.

Do you mean the impedance of the mains source, when driven as a load?

This varies widely over frequency, and is heavily dependent on location and service class.

This is an RF study of a typical household:

Power line modem proposals like CENELEC SC205A make good reading.

At the power frequency, impedances are characterized by loading effects and may be in the tens of milliohms.

RL

There's a measurement technique suggested by Kwasniok, Bui, Kozlowski and Stuchly in the IEEE Transactions on EMC Vol35 #1 Feb'93.

RL

It is not. Every conductor has a capacitance and inductance. Because of the vast distances of the mains grid, the inductance has a significant influence. The mains is not only used to supply power, but also to remote control stuff like lantarns and metering devices (over here there is a day and night tarif). And there are all kinds of standard to transport data over mains. My guess is the OP wants to build or use a device that transports data over the mains.

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If it\'s being measured, then the premise is that when the
measurement is completed the impedance will be known.  If not by
some one then by some thing... 

Better worded would have read: "Yes.  Any large commercial user of
energy does because the power company charges them for volt-ampere
hours and the power factor correction machinery needs to know the
line impedance so it can bring the power factor to unity with the
load connected to the mains."

Suppose that someone wanted to generate 3kW on the power line the equation to calculate this power would be

{[(VgeneratorPeak - VlinePeak)/sqrt(2)]^2}/LineImpedence = 3kW

Is this correct?

If the impedence is high then the generator peak voltage must also be high. Unless you had a way to change your generator peak voltage you cannot reliably generate 3kW, since you are at the mercy of the local line impedence.

Scott

Don't seem to be able to get a link posted through the mail server.

Google for an article by Montoya on Power Line Communications. Theres a nice graph showing impedance ranges measured above 1KHz..

If you are talking about pumping power into the mains, there are a growing number of standards that cover this kind of grid linked interface. Google some terms.

Weak-Grid, micro-grid, nanogrid, distributed generators, grid interconnections standard, grid-conected inverter.

The instances where client a would be expected to produce exactly

3.00KW into a distribution node are infinitessimal. Thats not how it works. The 'generator' has a reference frequency and phase, with acceptible distortion limits.

Running voltage sources in parallel requires compensation, if only the crudest of sharing chokes. If the load on the two sources is nonlinear, it's not the responsibility of just one of those sources to compensate, it's a shared responsibility. Under those cicumstances, your generator should probably be configured to act as a sinusoidal current source, locked to the grid frequency, as there's no way your own impedance will match the capability of the larger utility.

RL

The impedance at our service entrance was measured as 1/10 ohm.

The way to avoid the problem you are anticipating is to sell power to the grid from a current source rather than a voltage source.

Selling from a voltage source whose waveshape is a good sinusoid can also lead to too high distortion of the current supplied to the grid because of the grid's own distortion.

That's a reasonable figure.

Assume a 15 kVA, 240V single phase transformer with a 2.5% impedance. That comes to 96 milliOhms impedance. Throw in a little more for the service drop and you get in the neighborhood of 0.1.

On the other end, residential service equipment is rated for a fault duty of 10,000 A. That gives you an impedance of about 24 milliOhms.

grid's

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