On May 5, 11:28=A0pm, "Phil Allison" <phi...@tpg.com.au> wrote:> <dagmargoodb...@yahoo.com> > > If you had a sample, the insulation rating of the wire would be a good > starting point for the upper limit... > > ** That assumes the ends of the coil are adjacent. > > Normally, the voltage between adjacent turns is divided by the number of > turns, for a single layer coil. > > Real tests need to be done on a real example - =A0cos insulation to the > ferrite may be the first to fail.I was assuming, as worst case, a conductive core. -- Cheers, James Arthur
Inductor Voltage Rating?
Started by ●May 5, 2013
Reply by ●May 6, 20132013-05-06
Reply by ●May 6, 20132013-05-06
On May 6, 4:16=A0pm, John Larkin <jlar...@highlandtechnology.com> wrote:> On Sun, 5 May 2013 19:46:01 -0700 (PDT), dagmargoodb...@yahoo.com > wrote: > > >On May 5, 8:57=A0pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote: > >> I have to make low power SMPS operable up to several hundred volts. Fo=r> >> obvious reasons, it would be good to use off the shelf SMT inductors. > >> In datasheets, they always specify inductor max. current, however they > >> don't say anything about max. voltage. > > >> Any advice or relevant experience? > > >> Vladimir Vassilevsky > >> DSP and Mixed Signal Designswww.abvolt.com > > >If you had a sample, the insulation rating of the wire would be a good > >starting point for the upper limit... > > Just remembered that a while back I tested a twisted pair of #40 > magnet wire for breakdown. This was at about 1200 volts DC, as I > recall. > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/WireArc.jpgNeat. Bzzzttt phffft!. I'd have some concern about a.c. HV vs. d.c.--a.c. exercises the dielectric. I'd expect high e-fields to accelerate wear. -- Cheers, James
Reply by ●May 7, 20132013-05-07
mike <ham789@netzero.net> wrote:> On 5/5/2013 8:28 PM, Phil Allison wrote: >> <dagmargoodboat@yahoo.com> >> >> If you had a sample, the insulation rating of the wire would be a good >> starting point for the upper limit... >> >> ** That assumes the ends of the coil are adjacent. >> >> Normally, the voltage between adjacent turns is divided by the number of >> turns, for a single layer coil. >> >> Real tests need to be done on a real example - cos insulation to the >> ferrite may be the first to fail. >> >> >> .... Phil >> >> >> > Tests good, but you're missing the point...SPECS BETTER! > > Shoot-From-The-Hip designers are a nightmare.> Back in the day, there was a whole building full of engineers > who did nothing but verify components met their specs.Western Electric?
Reply by ●May 7, 20132013-05-07
On Monday, May 6, 2013 2:57:27 AM UTC+2, Vladimir Vassilevsky wrote:> I have to make low power SMPS operable up to several hundred volts. For > > obvious reasons, it would be good to use off the shelf SMT inductors. > > In datasheets, they always specify inductor max. current, however they > > don't say anything about max. voltage. > > > Any advice or relevant experience? >I have used the Bourns SDR0805 for a 15V buck converter with 400VDC input. Upon request, the manufactor has stated that the inductor is good for 600VDC http://www.bourns.com/pdfs/SDR0805.pdf AFAIR, at these voltages you need to be carefull that you will not get corona discharge effects, but at least we didn't see any during the testing. Cheers Klaus
Reply by ●May 7, 20132013-05-07
Klaus Kragelund wrote:> On Monday, May 6, 2013 2:57:27 AM UTC+2, Vladimir Vassilevsky wrote: >> I have to make low power SMPS operable up to several hundred volts. >> For >> >> obvious reasons, it would be good to use off the shelf SMT >> inductors. >> >> In datasheets, they always specify inductor max. current, however >> they >> >> don't say anything about max. voltage. >> >> >> Any advice or relevant experience? >> > > I have used the Bourns SDR0805 for a 15V buck converter with 400VDC > input. Upon request, the manufactor has stated that the inductor is > good for 600VDC >That is the correct way to do it with such high voltages. Ask the manufacturer for a statement, preferably in writing. Anything else would IMHO be irresponsible when doing a product design.> http://www.bourns.com/pdfs/SDR0805.pdf > > AFAIR, at these voltages you need to be carefull that you will not > get corona discharge effects, but at least we didn't see any during > the testing. >It can become a concern if used in other climate zones. Sometimes coating or potting can help. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●May 7, 20132013-05-07
Robert Baer wrote:> Vladimir Vassilevsky wrote: >> >> I have to make low power SMPS operable up to several hundred volts. For >> obvious reasons, it would be good to use off the shelf SMT inductors. >> In datasheets, they always specify inductor max. current, however they >> don't say anything about max. voltage. >> >> Any advice or relevant experience? >> >> Vladimir Vassilevsky >> DSP and Mixed Signal Designs >> www.abvolt.com > Any inductor can have a voltage rating; that depends on the wire > insulation (lacquer, beldasol, etc) and should be less that the volts > per turn mitigated by how many turns from one wire to physically next wire. > At high frequencies, it is prolly reduced a lot. >As a teenager I found that out the hard way with an RF power amp design, tubes. BIG tubes. Used it at higher frequencies, worked, yeehaw! Then ... tzzt ... pop .. pop-pop ... PHSSSST ... *PHOOOF* ... plate current meter briefly pegged ... thwock .. all lights out. It had tripped the mains breaker. After disecting it turned out that the plate choke had completely clumped and welded together, leaving spatters all around it. An amperage smell wafted through the house. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●May 7, 20132013-05-07
On Sun, 05 May 2013 19:57:27 -0500, Vladimir Vassilevsky <nospam@nowhere.com> wrote:> >I have to make low power SMPS operable up to several hundred volts. For >obvious reasons, it would be good to use off the shelf SMT inductors. >In datasheets, they always specify inductor max. current, however they >don't say anything about max. voltage. > >Any advice or relevant experience? > >Vladimir Vassilevsky >DSP and Mixed Signal Designs >www.abvolt.comAt higher voltages you'll find that core loss becomes a more serious factor in rise, as you're tempted to minimize turns and allow increased ripple current. Inductors can be used in series, if off-the-shelf parts look a little fragile, construction-wise. Deconstruct a few and eyeball internal layer and winding/core stress, if in doubt. RL
Reply by ●May 8, 20132013-05-08
On May 7, 6:56=A0pm, legg <l...@nospam.magma.ca> wrote:> On Sun, 05 May 2013 19:57:27 -0500, Vladimir Vassilevsky > > <nos...@nowhere.com> wrote: > > >I have to make low power SMPS operable up to several hundred volts. For > >obvious reasons, it would be good to use off the shelf SMT inductors. > >In datasheets, they always specify inductor max. current, however they > >don't say anything about max. voltage. > > >Any advice or relevant experience? > > >Vladimir Vassilevsky > >DSP and Mixed Signal Designs > >www.abvolt.com > > At higher voltages you'll find that core loss becomes a more serious > factor in rise, as you're tempted to minimize turns and allow > increased ripple current. > > Inductors can be used in series, if off-the-shelf parts look a little > fragile, construction-wise. > > Deconstruct a few and eyeball internal layer and winding/core stress, > if in doubt. > > RLBe aware when using heat dissipating devices in series that a lot of that heat is intended to leave via the end terminations. Which means the end attached to another will not be losing heat as fast as you thought. Two in series we used to dreate a bit something like to 70% of what you can do with one. And for three in series, well the center one is going to get the hottest. To mitigate a bit, we'd use oversized metal pours around the connections. Helped a bit.
Reply by ●May 12, 20132013-05-12
On Sun, 05 May 2013 19:57:27 -0500, Vladimir Vassilevsky <nospam@nowhere.com> wrote:> >I have to make low power SMPS operable up to several hundred volts. For=20 >obvious reasons, it would be good to use off the shelf SMT inductors. >In datasheets, they always specify inductor max. current, however they=20 >don't say anything about max. voltage. > >Any advice or relevant experience? > >Vladimir Vassilevsky >DSP and Mixed Signal Designs >www.abvolt.comNot so much as experience, but some relatively sound advice. Wire insulation withstand comes in voltage ratings, like low voltage 50 V or less, 300 V or less, 600 V or less, 1000 V or less. Select for insulation voltage rating to suit your needs. =20 See NFPA 70 "National Electrical Code" and=20 ANSI/IEEE C2 "National Electrical Safety Code". It also comes in temperature grades which are related to the hottest part of the winding. That location varies a bit due to winding dimensions and core losses with attendant core temperature rise. See: http://en.wikipedia.org/wiki/Insulation_system ?-)
Reply by ●May 12, 20132013-05-12
