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Parasitic capacitance in inductors

J

John Larkin

Jan 1, 1970
0
You are turning it into a distributed component, Bowick is mainly
concerned with lumped elements.

If Bowick thinks that the distributed capacitance of a coil is caused
by its resistance, then he is a lumped element.

John
 
P

pat dot lawler att verizon dott nneett

Jan 1, 1970
0
The actual quote from Bowick's book (at page 15) is:
"Real-World Inductors
"As we have discovered in preverous section of this chaptre, there is
not perfect component and inductors are certainly no exception. As a
matter of fact, of the components we have discussed, the inductor is
probably the component most prone to very drastic changes over
frequency.... As previously dicussed, whenever we bring two conductors
into close proximity but separated by a dielectric and place a voltage
differential between the two, we form a capactitor. Thus if any wire
resistance at all exists, a voltage drop (even though very minute)
will occcur between the widings, and small capacitors will be formed.
This effect is called distributed capacitance."

So this explanation is definitely wrong, then?

How about 'impedance', instead of resistance?

"Thus if any wire _impedance_ at all exists, a voltage drop (even
though very minute) will occur between the windings, ..."
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that John Larkin <jjlarkin@highlandSNIP
techTHISnologyPLEASE.com> wrote (in <99qprvk57tsoii6ird674g4o5l7k0neo0j@
4ax.com>) about 'Parasitic capacitance in inductors', on Thu, 20 Nov
2003:
If Bowick thinks that the distributed capacitance of a coil is caused by
its resistance, then he is a lumped element.

He doesn't say that. What he effectively says is that even at
arbitrarily low frequencies the resistance of each turn produces a
voltage across the inter-turn capacitance. This is true, but it is far
from the whole story, which is what I commented initially.
 
B

Ben Bradley

Jan 1, 1970
0
In sci.electronics.design, pat dot lawler att verizon dott nneett
wrote:
How about 'impedance', instead of resistance?

"Thus if any wire _impedance_ at all exists,

And since its an inductor conducting an AC current, such impedance
DOES exist (or more correctly it always exists, the inductive
reactance part is greater than zero for ac and is zero for DC).
a voltage drop (even
though very minute) will occur between the windings, ..."

For an alternating current, inductance is an impedance (a general
term) or a reactance (a more specific term) - there will be a voltage
drop between adjacent windings, even if the resistance is zero. In
practical inductors, at the usual frequencies of interest, the
inductive reactance accounts for much more of the voltage difference
between windings than does the resistance.
 
P

Paul Burridge

Jan 1, 1970
0
It's cool that the prop velocity of an electrical signal traveling
down a bare wire is just coincidentally equal to the velocity of an EM
wave in free space. That's why a wire makes a good antenna.

It's not though, is it? The propagation velocity in wire is somewhat
slower than that in air. That's why one has to multiply it by the
'free space correction factor' - something in the region of 97% of
light speed, IIRC.
 
P

Paul Burridge

Jan 1, 1970
0
You are turning it into a distributed component, Bowick is mainly
concerned with lumped elements.

Bowick actually refers to this parasitic capacitance between turns as
"distributed". I'm still waiting for the Panel to come to a definitive
conclusion as to whether Bowick's explantation, which I have
reproduced here verbatim, is accurate or not. Is the quote given from
his book correct or not?
 
P

Paul Burridge

Jan 1, 1970
0
For given dimensions and number of turns on a single-layer solenoid
calculate all characteristics of interest, including stray capacitance and
self-resonant frequency.

Make yourselves familiar with the magnitudes involved.

Download self-contained program SOLNOID3 in a few seconds and run
immediately.

And well worth it, I'm sure. Reg, do you have any programs in your
remarkable collection that tackle the problems of maximising radiated
power of (far from) non-ideal antennas for clandestine operation?
 
J

John Popelish

Jan 1, 1970
0
Paul said:
Bowick actually refers to this parasitic capacitance between turns as
"distributed". I'm still waiting for the Panel to come to a definitive
conclusion as to whether Bowick's explantation, which I have
reproduced here verbatim, is accurate or not. Is the quote given from
his book correct or not?

It is not close enough to right to be useful.
 
R

Reg Edwards

Jan 1, 1970
0
do you have any programs in your
remarkable collection that tackle the problems of maximising radiated
power of (far from) non-ideal antennas for clandestine operation?

========================

You don't need a program. Just turn up the wick.

========================
"I expect history will be kind to me, since I intend to write it."
========================

Winny was disappointed, eh?

Reg, G4FGQ ;o)
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Paul Burridge
[email protected]>) about 'Parasitic capacitance in inductors', on Fri, 21 Nov
2003:
Bowick actually refers to this parasitic capacitance between turns as
"distributed". I'm still waiting for the Panel to come to a definitive
conclusion as to whether Bowick's explantation, which I have reproduced
here verbatim, is accurate or not. Is the quote given from his book
correct or not?

I repeat that it's true, but it's not the WHOLE truth. The per-turn
resistance DOES create a voltage across the inter-turn capacitance, but
in the frequency range where the per-turn inductive reactance is
comparable with or far exceeds the per-turn resistance, the voltage due
to the inductive reactance also appears across the inter-turn
capacitance.

The inter-turn capacitance is there whether there is any current in the
inductor or not. So where the voltage across it comes from is a question
quite separate from that about the existence of the capacitance.
 
F

Fred Bloggs

Jan 1, 1970
0
Paul said:
Bowick actually refers to this parasitic capacitance between turns as
"distributed". I'm still waiting for the Panel to come to a definitive
conclusion as to whether Bowick's explantation, which I have
reproduced here verbatim, is accurate or not. Is the quote given from
his book correct or not?

We're not talking about that kind of "distributed." The distributed
component I'm talking about dimensionally spans a significant fraction
of a wavelength of the operating frequency.
 
P

Paul Burridge

Jan 1, 1970
0
========================

You don't need a program. Just turn up the wick.

Yeah, but then the final trannie goes 'pop' due to the appalling
mismatch caused by a (necessarily) folded-up ariel.
 
R

Rich Grise

Jan 1, 1970
0
The resistance doesn't have anyhting to do with the capacitance,
except when they're interacting. The capacitance is because
there are two conductors separated by an insulator. It just
sits there, so to speak. :)

Cheers!
Rich
 
P

Paul Burridge

Jan 1, 1970
0
The resistance doesn't have anyhting to do with the capacitance,
except when they're interacting. The capacitance is because
there are two conductors separated by an insulator. It just
sits there, so to speak. :)

So are you saying there doesn't need to be any potential difference to
arise between the turns for there to be an inter-turn capacitance?
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Paul Burridge
[email protected]>) about 'Parasitic capacitance in inductors', on Wed, 26 Nov
2003:
So are you saying there doesn't need to be any potential difference to
arise between the turns for there to be an inter-turn capacitance?

Indeed. An uncharged capacitor doesn't cease to exist.
 
P

Paul Burridge

Jan 1, 1970
0
I read in sci.electronics.design that Paul Burridge
[email protected]>) about 'Parasitic capacitance in inductors', on Wed, 26 Nov
2003:

Indeed. An uncharged capacitor doesn't cease to exist.

I think that's a metaphysical question that more properly belongs to
the realm of philosophy, John. :)
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Paul Burridge
[email protected]>) about 'Parasitic capacitance in inductors', on Thu, 27 Nov
2003:
I think that's a metaphysical question that more properly belongs to
the realm of philosophy, John. :)
I checked before making such a controversial statement. I short-
circuited some of the capacitors in my stock, and they didn't disappear.
 
P

Paul Burridge

Jan 1, 1970
0
I read in sci.electronics.design that Paul Burridge
[email protected]>) about 'Parasitic capacitance in inductors', on Thu, 27 Nov
2003:
I checked before making such a controversial statement. I short-
circuited some of the capacitors in my stock, and they didn't disappear.

Ah, but shorted them at what frequency?
;->
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Paul Burridge
[email protected]>) about 'Parasitic capacitance in inductors', on Thu, 27 Nov
2003:
Ah, but shorted them at what frequency?
;->
About one every 20 seconds, I think.
 
P

Paul Burridge

Jan 1, 1970
0
I read in sci.electronics.design that Paul Burridge
[email protected]>) about 'Parasitic capacitance in inductors', on Thu, 27 Nov
2003:
About one every 20 seconds, I think.

Very good. :) It obviously took you a while to think that one up.
 
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