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permanent magnets as coil cores

V

vinhkan

Jan 1, 1970
0
I recently came across an inductive charger that uses permanent
magnets as cores for the coils. What benefit does using a permanent
magnet have. Could someone direct me to some information on this
subject.
 
N

nospam

Jan 1, 1970
0
vinhkan said:
I recently came across an inductive charger that uses permanent
magnets as cores for the coils. What benefit does using a permanent
magnet have. Could someone direct me to some information on this
subject.

Causing the two coils to align themselves would seem to be an obvious
benefit.

--
 
V

vinhkan

Jan 1, 1970
0
Pre-biasing the operating point on the B-H curve ??

...Jim Thompson


Ok, that's right. I didn't think of that. Just never seen it before.
 
V

vinhkan

Jan 1, 1970
0
... so the remanence field strength is of opposite polarity and
approximately equal magnitude to the field from the DC and low-frequency
content of the current in the winding, increasing the margin against loss of
incremental permeability and saturation of the core?

Chris
Hmmm, interesting.
 
T

Tim Williams

Jan 1, 1970
0
Those things are in, yeah every single monitor I've taken apart. Always
something there that clings to your pliers when you desolder it. :)

In particular, I think they're usually wound from Litz wire, and found in
the horizontal deflection circuits. I seem to recall one was used in an
Apple monitor as a flyback supply for something, switched by an IRF640. I
don't remember if that was supplying power to the FBT, that's usually
supplied by the power supply itself...

Tim
 
L

legg

Jan 1, 1970
0
I recently came across an inductive charger that uses permanent
magnets as cores for the coils. What benefit does using a permanent
magnet have. Could someone direct me to some information on this
subject.

You may be mistaken. It is more likely that a small section of a core
is pre-biased, as the materials used for PM tend to be poor candidates
for efficient HF AC flux imposition.

Some polymer composite material and is used in LF motorc - which is
where magnetized material finds more frequent use.

Hitachi used to sell pre-biased E-core magnetics under the 'Hicoil',
'Hicoil-L' and 'Hiformer' trade marks, for applications below 100W and
40KHz. An EDN article from July 19, '78. It's not the kind of product
feature that would be easily recognized.

If your device is a non-contact inductively coupled charger, which the
term 'inductive charger' suggests, the presence of permanent magnets
may have nothing to do with efficient power conversion, and more to do
with maintaining coupler surface contact and orientation in the
charging station.

RL
 
R

Rich Grise

Jan 1, 1970
0
I recently came across an inductive charger that uses permanent
magnets as cores for the coils. What benefit does using a permanent
magnet have. Could someone direct me to some information on this
subject.

Guitar pickups are like that, because the string isn't magnetized,
so the coil just senses the changes in the flux when the string
vibrates. But I don't know how it would contribute to a "charger";
albeit you haven't really defined the term "charger" in this
context.

Good Luck!
Rich
 
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