Then why would a 10 A surge change their characteristics?
Unless it cracks it?
- Robert -
-----Original Message-----
From: Robert Wilson <[email protected]>
To: Robert Macy <[email protected]>; [email protected]
<[email protected]>
List-Post: [email protected]
Date: Thursday, June 06, 2002 8:51 AM
Subject: RE: ferrite transient voltage/current response
Soft Ferrites cannot be permanently magnetized. This is precisely why
they are used as beads and cores.
Bob Wilson
TIR Systems Ltd.
Vancouver.
-----Original Message-----
From: Robert Macy [mailto:[email protected]]
Sent: June 5, 2002 11:20 PM
To: [email protected]; [email protected]
Cc: [email protected]
Subject: Re: ferrite transient voltage/current response
He may have magnetized it. Degaussing with one of those Radio Shack
thingies would probably brought it back. Can he try it again?
- Robert -
Robert A. Macy, PE [email protected]
408 286 3985 fx 408 297 9121
AJM International Electronics Consultants
619 North First St, San Jose, CA 95112
-----Original Message-----
From: [email protected] <[email protected]>
To: [email protected] <[email protected]>
Cc: [email protected] <[email protected]>
List-Post: [email protected]
Date: Wednesday, June 05, 2002 2:52 PM
Subject: RE: ferrite transient voltage/current response
>
>
>
>While I was at Agilent in Spokane, one of the engineers or technicians
claimed
>that he had changed the RF characteristics of a 6-hole ferrite bead
(wound
with
>2 1/2 turns) used on a power supply trace to a noisy assembly. The
normal
>current was about 1 amp, but he accidently shorted the power supply
voltage
>after the inductor. This caused a current spike as the power supply
filter
>capacitor discharged (and then the supply current limited at about 10
amps).
>After this, there was a problem with RF leakage from the assembly.
Replacing the
>inductor fixed the problem. Apparently the effect was repeatable.
>
>I didn't observe this personally, so I can't guarantee it.
>
>Don Borowski
>Schweitzer Engineering Labs
>
>
>Sorry that I wasn't clear; I typically try to keep my questions general
so
> not to get too detailed about the specific application. And
thanks to
Bob,
> Chris and Mike who have responded ... putting it into Chris's
words
... I
> was just trying to find out if ferrites had ratings to prevent
them
from
> "j
> ust plain blowing the ferrite to smithereens". Also, I was
looking
for a
> shortcut if someone else had faced this question rather than
reading
> through all of the vendor web sites.
>
> I understand and have used ferrites quite often for typical EMI
>suppression; the ferrites typically being rated for the application
>currents, voltages, etc. In this case, the program is trying to
protect a
>power supply input from the DO-160 waveform 5B pin injected lightning
pulse
>of 300 volts open circuit & 300A short circuit. If the Gas Discharge
Tube
>is located past (closer to the supply which was done for packaging
>limitations) than the "T" EMI filter, a question was raised as to
whether
>the ferrite properties would be altered by the lightning pulse. Most
of
>the standard literature on the use of ferrites does not address these
types
>of transients.
>
>
>Susan Beard
>
>
>
>
>
>
>
>"Robert Wilson" <[email protected]>@majordomo.ieee.org on
06/04/2002
>02:16:48 PM
>
>Please respond to "Robert Wilson" <[email protected]>
>
>Sent by: [email protected]
>
>
>To: <[email protected]>, <[email protected]>
>cc:
>
>Subject: RE: ferrite transient voltage/current response
>
>
>
>Your question is not all that clear. It appears to imply that
transients
>have an affect on the ferrite beads, but it is the other way around
>(maybe that is what you meant). But in general, small ferrite beads
have
>little effect, except at very high frequencies (hundreds of MHz),
unless
>they are no longer "beads" (i.e. they are very large).
>
>Have a look at the various magnetics vendors data sheets and app notes.
>
>Magnetics Inc: www.mag-inc.com
>Fair-Rite Inc: www.fair-rite.com (whoever came up with THAT name should
>be shot!
>Steward Inc: www.steward.com
>Ferroxcube: www.ferroxcube.com
>Epcos (was Siemens): www.epcos.com
>
>
>Bob Wilson
>TIR Systems Ltd.
>Vancouver.
>
>-----Original Message-----
>From: [email protected] [mailto:[email protected]]
>Sent: June 4, 2002 8:57 AM
>To: [email protected]
>Subject: ferrite transient voltage/current response
>
>
>Could someone point me to some good App Note information on the
response
>of
>and affect on ferrite beads to transient voltage & current waveforms?
>The
>waveforms are based on the indirect lightning pulses specified in
>Section
>22 of DO-160.
>
>Thanks in advance,
>Susan Beard
>
>
>This e-mail may contain SEL confidential information. The opinions
expressed
>are not necessarily those of SEL. Any unauthorized disclosure,
distribution or
>other use is prohibited. If you received this e-mail in error, please
notify
>the sender, permanently delete it, and destroy any printout. Thank
you.
>
>
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