Inductor DC current rateing peak current
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From: Hammy on 6 Jul 2010 08:21 I'm looking for a 390uH inductor for a Boost PFC choke 250W output power. After spending some time browsing data sheets,I'm confused why only the DC current rating is shown. There is never any graph for current vs inductance or inductance vs frequency or max peak current to avoid saturation or graphs for core loss. From looking at a data sheet on a Bourns vertical mount Toroid 560uH @1kHz They specify at rated DC current an inductance drop from the original 560uH to 314.18uH. My PFC choke specifications at 65kHz are 4.9Apk and 3Arms would the 2321 560uH 3.6A one here be a possible candidate? http://www.bourns.com/data/global/pdfs/2300_series.pdf I could use a coilcraft part I have but its bigger then I would like to use part C1062-BL http://www.coilcraft.com/pdfs/c1061.pdf Note the detailed specs compared to 99% of the other inductor datasheets.
From: Bill Sloman on 6 Jul 2010 08:45 On Jul 6, 2:21 pm, Hammy <s...(a)spam.com> wrote: > I'm looking for a 390uH inductor for a Boost PFC choke 250W output > power. > > After spending some time browsing data sheets,I'm confused why only > the DC current rating is shown. There is never any graph for current > vs inductance or inductance vs frequency or max peak current to avoid > saturation or graphs for core loss. Inductance versus frequency is to some extent documented by the self- resonance frequency of the inductor, which is usually given. You can convert it to a parallel capacitance. The Bourns parts are wound with a single layer of widely separated turns of wire, for which the parallel capacitance usually comes out as of the order of 1pF, which would put the lowest self-resonant frequency around 5MHz and the highest closer to 50MHz It could be that the losses due to induced currents in the core would kill any such resonance, but pre-wound inductors are pretty much always designed such that the self-resonance is tolerably sharp, so that the inter-winding capacitance sets your upper frequency limit. Commercial pre-wound indusctors are generally designed so that they don't saturate below the DC current rating at the maximum rated working temperature - which is usually set by the Curie temperature of the core material. > From looking at a data sheet on a Bourns vertical mount Toroid 560uH > @1kHz They specify at rated DC current an inductance drop from the > original 560uH to 314.18uH. > > My PFC choke specifications at 65kHz are 4.9Apk and 3Arms would the > 2321 560uH 3.6A one here be a possible candidate? > > http://www.bourns.com/data/global/pdfs/2300_series.pdf > > I could use a coilcraft part I have but its bigger then I would like > to use part C1062-BL > > http://www.coilcraft.com/pdfs/c1061.pdf > > Note the detailed specs compared to 99% of the other inductor > datasheets. -- Bill Sloman, Nijmegen
From: Hammy on 6 Jul 2010 09:04 Bill Sloman wrote >Inductance versus frequency is to some extent documented by the self- >resonance frequency of the inductor, which is usually given. You can >convert it to a parallel capacitance. SRF is not given in the 1 page data sheet. >The Bourns parts are wound with a single layer of widely separated >turns of wire, for which the parallel capacitance usually comes out as >of the order of 1pF, which would put the lowest self-resonant >frequency around 5MHz and the highest closer to 50MHz > >It could be that the losses due to induced currents in the core would >kill any such resonance, but pre-wound inductors are pretty much >always designed such that the self-resonance is tolerably sharp, so >that the inter-winding capacitance sets your upper frequency limit. > >Commercial pre-wound indusctors are generally designed so that they >don't saturate below the DC current rating at the maximum rated >working temperature - which is usually set by the Curie temperature of >the core material. I would hope it wouldnt satuarate below the DC limit or else the spec would be useless.From what I recall any rateing DC or RMS current is set by copper losses peak current is set by core material and size.A massed produced inductor isnt going to use oversized cooper if the core cant handle the energy. They show a 43% drop in inductance at rated current. The core material is'nt stated but I'm guessing it is'nt ferrite.
From: Tim Williams on 6 Jul 2010 09:45 "Hammy" <spam(a)spam.com> wrote in message news:1s96365pokujmv0pquuj6be8odohb539hu(a)4ax.com... > They show a 43% drop in inductance at rated current. The core material > is'nt stated but I'm guessing it is'nt ferrite. If they have a color photo, you can guess the material type. http://www.micrometals.com/materials_index.html Mix 26 and 52 are quite popular, and fairly lossy (e.g., a typical DCM boost supply will have very little "dead time" ringing using these, whereas a ferrite core, with much lower losses, will ring significantly). Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: Hammy on 6 Jul 2010 13:04
On Tue, 6 Jul 2010 08:45:46 -0500, "Tim Williams" <tmoranwms(a)charter.net> wrote: >"Hammy" <spam(a)spam.com> wrote in message news:1s96365pokujmv0pquuj6be8odohb539hu(a)4ax.com... >> They show a 43% drop in inductance at rated current. The core material >> is'nt stated but I'm guessing it is'nt ferrite. > >If they have a color photo, you can guess the material type. >http://www.micrometals.com/materials_index.html >Mix 26 and 52 are quite popular, and fairly lossy (e.g., a typical DCM boost supply will have very little "dead time" ringing using these, whereas a ferrite core, with much lower losses, will ring significantly). > >Tim Well yes I guess I could , but should you really have too? They are trying to sell a product so they should be providing the information without someone having to jump through a bunch of hoops. You would figure they would have more detailed specs on their site but after browsing through the site and their catalogues they don't. If I wanted to build 5k a year what do you have to do email some clown in sales and ask for specifications that should already be included in the data sheet. I'm not just talking about the one inductor I posted about but the majority of inductor data sheets,if they can even be called that only state a dc current rating and maybe Q and srf. I'm just going to use the coilcraft part at least I know what I can expect. Its for a NCP1654 "CCM" boost converter. |