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Inductor Voltage Rating?

Started by Vladimir Vassilevsky May 5, 2013
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
On May 5, 5:57=A0pm, 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
First I'd make sure the pads are far enough apart to stand off whatever voltage you expect to create (+ safety factor of three or so). Then, have you looked here: http://www.digikey.com/product-search/en/transformers/switching-converter-s= mps-transformers/787670 Mark L. Fergerson
On Sun, 05 May 2013 19:57:27 -0500, 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?
Yes. If you're going to ask the the electronics equivalent of a question that would earn you a "Stupident" title change from some guy named Vladimir Vassilevsky on comp.dsp -- change your ways. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
"Vladimir Vassilevsky"
> > 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?
** Why not get a few likely candidates and test them to destruction ? Then you will know the absolute max and can de-rate from there. Eg: place the DUT in series with a high voltage ceramic cap and drive the combo at resonance with a sine wave from an amplifier - should be easy enough to get a few hundred volts RMS across the inductor. .... Phil
On Sun, 05 May 2013 21:04:21 -0500, Tim Wescott
<tim@seemywebsite.please> wrote:

>On Sun, 05 May 2013 19:57:27 -0500, 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? > >Yes. If you're going to ask the the electronics equivalent of a question >that would earn you a "Stupident" title change from some guy named >Vladimir Vassilevsky on comp.dsp -- change your ways.
>:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
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. 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 Designswww.abvolt.com
If you had a sample, the insulation rating of the wire would be a good starting point for the upper limit... -- Cheers, James Arthur
On 5/5/2013 7:05 PM, Phil Allison wrote:
> "Vladimir Vassilevsky" >> >> 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? > > > ** Why not get a few likely candidates and test them to destruction ? > > Then you will know the absolute max and can de-rate from there. > > Eg: place the DUT in series with a high voltage ceramic cap and drive the > combo at resonance with a sine wave from an amplifier - should be easy > enough to get a few hundred volts RMS across the inductor. > > > > .... Phil > >
I call that the "diode" method. Good for weeding out devices that definitely won't work...but says nothing about those that pass, out of the next batch...and the batch two years from now after the vendor quits making 'em. Certainly better than nothing, but nowhere near as helpful as contacting the vendors. Having a clear goal, like "several hundred volts" helps a lot. Several people really hate this method. The purchasing agent who has to source the thing. The safety compliance agent who's looking at something potentially unsafe with no specification. The manufacturing manager waiting for you to get the line back up. The guy in Field Returns who has to fix 'em. Your successor saddled with your comfort with risk taking. But, at least, you had fun smoking some.
<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



"mike"
 Phil Allison wrote:

>> ** Why not get a few likely candidates and test them to destruction ? >> >> Then you will know the absolute max and can de-rate from there. >> >> Eg: place the DUT in series with a high voltage ceramic cap and drive the >> combo at resonance with a sine wave from an amplifier - should be easy >> enough to get a few hundred volts RMS across the inductor. >> >> >> > I call that the "diode" method. Good for weeding out devices that > definitely won't work...but says nothing about those that pass, > out of the next batch...and the batch two years from now after > the vendor quits making 'em.
** My idea is to test *every example* at several times the max expected peak voltage - assuming this gives you a high pass rate.
> Certainly better than nothing, but nowhere near as helpful as contacting > the vendors.
** When using an un-speced parameter - one is on ones own. ... Phil
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. Hard to do when they don't have a spec. They would not let us do unspecified things that seemed to over-stress the technology...unless we didn't tell 'em. My engineers were trained to create reliable stuff. YMMV