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Impedance at HV

T

Tim Esser

Jan 1, 1970
0
Can someone please explain, given a fixed impedance load (say 600
ohms), how raising the voltage of the source to several hundred volts
affects matching efficiency?

IOW, in gerneral, as the voltage of an applied AC signal increases
does impedance matching become progressively less of a concern? If so,
why?

I am looking at the 1KHz to 1MHz bandwidth.

Tim Esser
 
P

Phil Allison

Jan 1, 1970
0
"Tim Esser"
Can someone please explain, given a fixed impedance load (say 600
ohms), how raising the voltage of the source to several hundred volts
affects matching efficiency?


** What makes you imagine it has any effect on efficiency ?

IOW, in gerneral, as the voltage of an applied AC signal increases
does impedance matching become progressively less of a concern?


** Impedance matching ( equal source and load ) is rarely ever a concern -
as it is so wasteful of power.

Your mysterious Q is impossible to answer unless you supply the context
where this idea has arisen.



....... Phil
 
Can someone please explain, given a fixed impedance load (say 600
ohms), how raising the voltage of the source to several hundred volts
affects matching efficiency?

Impedance matching ensures that the maximum amount of power is
deliverd to the load for a given output impedance. This property is
not a function of voltage. However, in circuits involving transfer of
large amounts of power, the major concern is power dissipation at the
source, and impedance matching is usually not important. Impedance
matching in the frequency range you're interested in would be a
concern only if reflections (ringing) at the load are a problem.
 
R

Robert Baer

Jan 1, 1970
0
Tim said:
Can someone please explain, given a fixed impedance load (say 600
ohms), how raising the voltage of the source to several hundred volts
affects matching efficiency?

IOW, in gerneral, as the voltage of an applied AC signal increases
does impedance matching become progressively less of a concern? If so,
why?

I am looking at the 1KHz to 1MHz bandwidth.

Tim Esser
Since you are implying a linear load, impedance matching has nothing
to do with signal level.
 
N

Nemo

Jan 1, 1970
0
Can someone please explain, given a fixed impedance load (say 600
ohms), how raising the voltage of the source to several hundred volts
affects matching efficiency?

The usual concern with raised voltages is that the things you apply them
to may not be rated at eg 600V, and the insulators in the coax, or
whatever you're using, break down (ie sparks, etc).

There is a (DC) ohmmeter colloquially called a "Megger" used to measure
resistance in mains-powered circuits. It does this at several hundred
volts, to test the insulation. Ie it is a micro-ammeter fed by a high
voltage supply. It is remarkable how many objects you think of as
insulators turn out to have significant conduction due to dirt on their
surface, etc at these voltages.
IOW, in gerneral, as the voltage of an applied AC signal increases
does impedance matching become progressively less of a concern? If so,
why?

I can't answer the question as I don't know, but as mentioned above I'd
be significantly concerned about components, cables etc blowing up when
subjected to more then their rated voltage. Apart from mains electricity
- where obviously you use a much lower impedance than 600 ohms - I don't
know where you'd use high voltage AC, except possibly when discussing an
ariel where the voltage along it can get quite high due to standing
waves.
 
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