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Amt of current to saturate ferrite rod

P

Paul Nelson

Is it technically possible to saturate a garden variety ferrite rod
(10mm dia. x 120mm long) with a single layer winding?

This assumes applied DC.

Paul Nelson
 
M

mike

Paul said:
Is it technically possible to saturate a garden variety ferrite rod
(10mm dia. x 120mm long) with a single layer winding?

This assumes applied DC.

Paul Nelson
Yes, to the degree that you can "saturate" any material.
Isn't saturation an asymptotic property that can't be fully achieved
this side of infinity?
So, depends on your definition of saturation.
 
T

Tim Williams

At least for moderate length rods (roughly 6 mm dia. x 30 mm long, often
seen in computer SMPSs), the change in inductivity is about half, so
you'll hardly notice it. The change is just as sharp as any ferrite
inductor though.

At an aspect ratio like that, you'll probably see more gradual saturation,
as the center becomes saturated first and the whole thing progressively
becomes an air-cored inductor.

Depending on what you're doing, rods often aren't wound all the way to the
end, because inductivity drops -- SWAG, fringing sucks down maybe half the
field out past 80% from the center. You occasionally also see multilayer
windings, which are great if the wire is thin, but only up to a winding
height about equal to the diameter. Think of the fields of a bar magnet,
they loop around pretty well from the ends, but any space within those
arcs is prime real estate for coil winding purposes.

Tim
 
S

Sjouke Burry

[email protected] (Paul Nelson) wrote in @news.tpg.com.au:
Is it technically possible to saturate a garden variety ferrite rod
(10mm dia. x 120mm long) with a single layer winding?

This assumes applied DC.

Paul Nelson

Yes.
 
A

admformeto

Paul Nelson said:
Is it technically possible to saturate a garden variety ferrite rod
(10mm dia. x 120mm long) with a single layer winding?

This assumes applied DC.

Paul Nelson

If you just want static saturation then use neodymium magnet.
The electromagnetic saturation will consume some power to the point that the
winding will start decapitating some heat so to avoid that multi layering
with thicker wire must be used.

Mathew Orman

http://www.faster-than-light.us/
 
J

John S

Is it technically possible to saturate a garden variety ferrite rod
(10mm dia. x 120mm long) with a single layer winding?

This assumes applied DC.

Paul Nelson

As others have pointed out, yes.

Also, as others have pointed out, how will you define saturation?

Addressing your subject line:

1 amp. (assumes 100 oersteds) (955 turns of wire over the 120mm)
or
10 amps. (assumes 100 oersteds) (95 turns of wire over the 120mm)
or
etc.

Of course, the 100 oersteds is probably overkill for what you're asking,
but who can tell at this point?
 
R

Ralph Barone

John S said:
As others have pointed out, yes.

Also, as others have pointed out, how will you define saturation?

Addressing your subject line:

1 amp. (assumes 100 oersteds) (955 turns of wire over the 120mm)
or
10 amps. (assumes 100 oersteds) (95 turns of wire over the 120mm)
or
etc.

Of course, the 100 oersteds is probably overkill for what you're asking,
but who can tell at this point?

And if you need more current, use an edgewound ribbon conductor. I agree,
the question is vague.
 
L

legg

[email protected] (Paul Nelson) wrote in @news.tpg.com.au:

Is it technically possible to saturate a garden variety ferrite rod
(10mm dia. x 120mm long) with a single layer winding?

This assumes applied DC.

Paul Nelson

You might apply the formula:

B = 4 x pi x 10^-7 x N x I / le

B = saturation flux density in Teslas ( ferrite ~ 0.3)
N = number of turns
I = DC current in Amps
Le = magnatic path length in Meters
- ( length of air path between rod ends)

As the ferrite saturates, le doubles, before B can continue to climb.

In practical situations, you'd be more concerned with temperature rise
in the copper. Because of the long gap, inductance and Q values are
pretty low, until you hit RF frequencies, but are better than
air-cored structures of comparable size.

RL

again server issues. every post is a frigging test....
 
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