On Apr 20, 7:39=A0am, default <edmoneyfromlanailstu...@[EMAIL PROTECTED]
>
wrote:
> On 19 Apr., 22:31, "hrhofm...@[EMAIL PROTECTED]
" <hrhofm...@[EMAIL PROTECTED]
> wrote:
>
>
>
>
>
> > On Apr 19, 11:07=A0am, default
<edmoneyfromlanailstu...@[EMAIL PROTECTED]
>
> > wrote:
>
> > > On 19 Apr., 04:32, "hrhofm...@[EMAIL PROTECTED]
" <hrhofm...@[EMAIL PROTECTED]
> wrote:
>
> > > > On Apr 18, 3:09=A0am, default
<edmoneyfromlanailstu...@[EMAIL PROTECTED]
>
> > > > wrote:
>
> > > > > I am writting at my diploma thesis with an EMC theme.
>
> > > > > If got a power fan (13V / 6A) witch produces conducted
emissions, =
so I
> > > > > have to reduce them to achieve CISPR25.
> > > > > Up to 40MHz I found an easy solving with LC lowpass filter, but
ov=
er
> > > > > 50MHz I am out of the CISPR25 limit.
>
> > > > > Does anybody have experiences in EMC design in high frequency
band=
s,
> > > > > doesn't have?
>
> > > > > I think about solving it like the motherboard producers do, they
> > > > > design there signals like little inductors and so one.
> > > > > But I didn't find any guidlines to do this like them.
>
> > > > Are you saying that the lowpass filter is not blocking the high-
> > > > frequency noise components above 45 MHz, but is blocking the
mid-ran=
ge
> > > > frequency components below 45 MHz, and so you need a more
effective
> > > > filter against the really high-frequency noise from 45 MHz and
> > > > higher? =A0
>
> > > yes that's my problem, downsides 45MHz it's okay
>
> > > Some ferrite beads on the power leads along with shunt
>
> > > > capacitance between the leads and between each lead on a good
solid
> > > > ground should form an effective high-frequency filter. =A0But lead
> > > > lengths are critical at these frequencies, beware of any leads
longe=
r
> > > > than 1 inch, these look as much like inductors as real inductors.
>
> > > i tried two X-C's form plus load to case of the fan and one from gnd
> > > to case, it works fine but the ****blem is that i can't do it.
> > > according to the opnion of my boss, because maybe there are new fans
> > > designed in future that doesn't have a metallic case.
>
> > > > How many dB are you over the limits, 10, 100???
>
> > > the worst case level is about 65MHz with 56dB=B5V and the spec is
abou=
t
> > > 30dB=B5V, i am circa 26dB=B5V above the debit level- Hide quoted
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>
> > > - Show quoted text -
>
> > If the new fans of the future have plastic cases, they will have to do
> > a better job inside the case of stopping the noise.. =A0Have you tried
> > any ferrite beads on the conductors on the fan side of the capacitors
> > to act as high impedances to the higher frequency noises?- Zitierten
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t ausblenden -
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> > - Zitierten Text anzeigen -
>
> did you mean like this?:
>
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> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)- Hide
quoted =
text -
>
> - Show quoted text -
Sorry - can't understand your drawing. Will sketch something up and
scan it. Have you tried reading any of the standard text books on
EMC???
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