The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: "Christopher R. Carlen"
Subject: Re: Core gapping techniques and general SMPS magnetics stuff
Date: Mon, 16 Dec 2002 11:09:55 -0800
Organization: Sandia National Laboratories, Albuquerque, NM USA
NNTP-Posting-Date: Mon, 16 Dec 2002 18:08:38 +0000 (UTC)
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.1) Gecko/20020826
X-Accept-Language: en-us, en
Harry Dellamano wrote:
> Hey Chris,
> Kiss off the clips and the center gap. Use tape, as mentended in this
> thread, to wrap the cores together for testing and pre production. This
> allows you to fine tune the gap with spacers on all three legs. One gap
> size fits all with ungapped cores with spaces. Why buy specially gapped
> cores? In production the decision is made weather to use clips or epoxy the
> gapped cores together.
> Remember that in flyback topology the magnetics is an inductor and if it
> has a secondary it is a coupled inductor, never a transformer therefore the
> secondary current does not cancel primary current because they never flow at
> the same time. The primary will saturate as a function of the L*I product.
> The gap is introduced to reduce the inductance so that the current can be
> increased to meet your L*I product needs which is equal to volt seconds
> across the primary winding. You will calculate L and I by circuit
> requirements and then control it by varying turns and gap to meet your L*I
> requirement. L=K*N^2 so it is a intuitive process to get an optimum design
> It turns out that spreading the gap across three legs instead of (x2) on
> the center leg, that the AC resistance of the winding is greatly reduced and
> the inductor is more efficient. 95% of the time the external fringing flux
> will not cause EMI to the rest of the system. If it does, rotate thre core
> or use the external shield as pointed out elsewhere in the thread.
Thanks for the info!
> good luck and don't let the smoke out
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup