From: "Christopher R. Carlen"
Subject: Re: 87% All that vector calculus paid off
Date: Tue, 24 Dec 2002 10:25:51 -0800
Organization: Sandia National Laboratories, Albuquerque, NM USA
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NNTP-Posting-Date: Tue, 24 Dec 2002 17:24:23 +0000 (UTC)
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Tony Williams wrote:
> It looks like 157mT B-pk is too high and causing the u-effective to
> roll off.
>> Maybe tonight I can check the current with a 1 ohm resistor,
> Look out for a slight upward curl at the end of the current ramp.
Didn't get to do it yet, but I know what to look for.
> It would also be interesting to see if the efficiency improves if the
> 2.7uS ON-time is reduced.
> An even wilder WAG; If you have 32 turns of (say) 0.8mm wire, then
> your I^2*R losses in the winding will be less than 200mW (if I've
> done the calcs right).
Ok, I didn't calculate this yet, I just put on a wire that "looked"
thick enough, and which I happened to have laying around.
> I don't have data on the core material, but would suspect that the
> core loss (swinging over 157mT @ 150000 times/sec) would be somewhat
> greater than 200mW.
Yeah, the core loss from my estimation based on ferroxcube's 3C90
graphs, is about (350+-50)kW/m^3
I also have some 3C94 cores, which will almost halve that. I'll have to
> It looks like there is margin there to swap some of the core loss for
> I^2*R loss, and so get a better energy transfer efficiency from the
> inductor. ie, increase the gap.
> We are just entering the realms of optimising a polarised
> inductor.... eg, Hannah curves.
Yes, I am thinking that I'll have to increase the gap to make it work
with a lower input voltage anyway. The gap is already quite large
I will also be curious to compare the behavior of a center gapped core
with a inner/outer legs gapped core.
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA