• Re: No voltage rating for inductors

    From jlarkin@highlandsniptechnology.com@21:1/5 to All on Sat Mar 5 15:59:03 2022
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    Of course, applying any significant DC voltage across an inductor is
    unlikely to have a good outcome, but one can certainly put a significant >voltage across one for a short period, and it would be nice to know what
    the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are
    close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's
    rare. The dual-winding guys, like DRQ127, are probably bifalar and
    have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good.

    Class D amp?



    --

    I yam what I yam - Popeye

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Sylvia Else@21:1/5 to All on Sun Mar 6 10:23:29 2022
    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    Of course, applying any significant DC voltage across an inductor is
    unlikely to have a good outcome, but one can certainly put a significant voltage across one for a short period, and it would be nice to know what
    the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are
    close together.

    Sylvia.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Sylvia Else@21:1/5 to jlarkin@highlandsniptechnology.com on Sun Mar 6 12:21:09 2022
    On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    Of course, applying any significant DC voltage across an inductor is
    unlikely to have a good outcome, but one can certainly put a significant
    voltage across one for a short period, and it would be nice to know what
    the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are
    close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's
    rare. The dual-winding guys, like DRQ127, are probably bifalar and
    have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good.

    Class D amp?




    No. I was pondering why LED light fittings need to have a large
    electrolytic capacitor with its limited life.

    I have a couple of small LEDs illuminating an otherwise frequently pitch
    black corridor. They're powered through a transformer, bridge rectifier
    and current limiter, with no capacitors at all. They obviously flicker
    at 100Hz, but it's not visible.

    So then I was thinking that one could use a buck converter directly off
    the rectified, but not filtered, mains, hence the voltage requirement.

    This has not moved past musings at this point, but I was looking at the
    voltage specs for inductors, hence my comment.

    Sylvia.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Anthony William Sloman@21:1/5 to Sylvia Else on Sat Mar 5 17:22:22 2022
    On Sunday, March 6, 2022 at 10:23:41 AM UTC+11, Sylvia Else wrote:
    I've looked at a number of data sheets, and they never seem to give a voltage rating.

    Of course, applying any significant DC voltage across an inductor is unlikely to have a good outcome, but one can certainly put a significant voltage across one for a short period, and it would be nice to know what
    the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are
    close together.

    Wound parts are mostly wound with double-enamelled copper wire, which is good to about 500V.
    Everybody is supposed to know this, which is why it won't get into the part data sheet.

    It is in the wire data sheets, but if you've never designed or wound a transformer (or choke/inductor) you may not know. None of the the obvious text books I've got to hand say anything about it, which is a bit odd. When I was graduate student I got to
    know a guy from Croatia (Ales Strojnik) who spent a year designing and building a 600 kV scanning electron microscope for the Melbourne Physics department, and I may have picked up some stuff from him.

    https://en.wikipedia.org/wiki/Ale%C5%A1_Strojnik

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Anthony William Sloman@21:1/5 to Sylvia Else on Sat Mar 5 17:30:56 2022
    On Sunday, March 6, 2022 at 12:21:21 PM UTC+11, Sylvia Else wrote:
    On 06-Mar-22 10:59 am, jla...@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <syl...@email.invalid> wrote:

    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    Of course, applying any significant DC voltage across an inductor is
    unlikely to have a good outcome, but one can certainly put a significant >> voltage across one for a short period, and it would be nice to know what >> the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are
    close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's
    rare. The dual-winding guys, like DRQ127, are probably bifalar and
    have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good.

    Class D amp?



    No. I was pondering why LED light fittings need to have a large
    electrolytic capacitor with its limited life.

    I have a couple of small LEDs illuminating an otherwise frequently pitch black corridor. They're powered through a transformer, bridge rectifier
    and current limiter, with no capacitors at all. They obviously flicker
    at 100Hz, but it's not visible.

    So then I was thinking that one could use a buck converter directly off
    the rectified, but not filtered, mains, hence the voltage requirement.

    This has not moved past musings at this point, but I was looking at the voltage specs for inductors, hence my comment.

    The problem with unfiltered mains is nearby lightning strikes, which can produce kilovolt spikes.

    It is known that every last local area network ever invented got blown up during the prototype stage by a nearby lighting strike, and even the famous Intel/DEC/Xerox Park Ethernet Standard had to be modified after it was first published to put in proper
    lightning protection.

    Transzorbs and spark-gaps can cope, if you are aware of the problem at the design stage.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jlarkin@highlandsniptechnology.com@21:1/5 to All on Sat Mar 5 19:12:34 2022
    On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    Of course, applying any significant DC voltage across an inductor is
    unlikely to have a good outcome, but one can certainly put a significant >>> voltage across one for a short period, and it would be nice to know what >>> the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and
    everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are
    close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's
    rare. The dual-winding guys, like DRQ127, are probably bifalar and
    have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good.

    Class D amp?




    No. I was pondering why LED light fittings need to have a large
    electrolytic capacitor with its limited life.

    I have a couple of small LEDs illuminating an otherwise frequently pitch >black corridor. They're powered through a transformer, bridge rectifier
    and current limiter, with no capacitors at all. They obviously flicker
    at 100Hz, but it's not visible.

    So then I was thinking that one could use a buck converter directly off
    the rectified, but not filtered, mains, hence the voltage requirement.

    This has not moved past musings at this point, but I was looking at the >voltage specs for inductors, hence my comment.

    Sylvia.

    Lots of LED bulbs have a bridge and a linear IC current limiter but no
    cap. A capless switcher is an interesting idea. The LED could run at
    constant current at a very high duty cycle.

    An inductor like you showed would be fine at hundreds of volts. Test
    one to breakdown!





    --

    I yam what I yam - Popeye

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to All on Sun Mar 6 12:25:43 2022
    On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    Of course, applying any significant DC voltage across an inductor is
    unlikely to have a good outcome, but one can certainly put a significant >>> voltage across one for a short period, and it would be nice to know what >>> the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and
    everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are
    close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's
    rare. The dual-winding guys, like DRQ127, are probably bifalar and
    have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good.

    Class D amp?




    No. I was pondering why LED light fittings need to have a large
    electrolytic capacitor with its limited life.

    I have a couple of small LEDs illuminating an otherwise frequently pitch >black corridor. They're powered through a transformer, bridge rectifier
    and current limiter, with no capacitors at all. They obviously flicker
    at 100Hz, but it's not visible.

    So then I was thinking that one could use a buck converter directly off
    the rectified, but not filtered, mains, hence the voltage requirement.

    This has not moved past musings at this point, but I was looking at the >voltage specs for inductors, hence my comment.

    Sylvia.

    Low voltage LED lighting and hardware is not mains-rated for safety.

    Their safe use is achieved through the isolation transformer, tested
    at the time of assembly to 3x book isolation ratings. The secondary
    circuit is SELV (Safe Extra Low Voltage).

    Led lamps that sub for incandescent bulbs in mains hardware are
    constructed with sufficient insulation between the electronics
    and the end user, to achieve safe use.

    Hardware running at SELV is subjected only to simple flammability
    and material/environmental regs.

    Mains inductors are invariably core-loss or VT limited, below their
    current ratings or corona susceptibility.

    If you crunch some numbers, you'll see why direct buck conversion
    off the mains, at low power, is not easily practised.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From whit3rd@21:1/5 to bill....@ieee.org on Sun Mar 6 13:51:41 2022
    On Saturday, March 5, 2022 at 5:22:29 PM UTC-8, bill....@ieee.org wrote:
    On Sunday, March 6, 2022 at 10:23:41 AM UTC+11, Sylvia Else wrote:
    I've looked at a number of data sheets, and they never seem to give a voltage rating.

    Wound parts are mostly wound with double-enamelled copper wire, which is good to about 500V.
    Everybody is supposed to know this, which is why it won't get into the part data sheet.

    Since the enamel insulation separates adjacent windings, it isn't the device rating at all; if
    there's 100 turns, at 1 kV, the adjacent turns have at least 10 volts across each two-layers,
    but possibly no more than that. The insulating former (for small power xformers) between
    windings and core is probably good for kilovolts. Spaghetti around the wires, and tape
    between layers, all add to the voltage-breakdown tolerance, as does pie-winding...

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Rich S@21:1/5 to All on Sun Mar 6 15:05:03 2022
    On Sunday, March 6, 2022 at 9:51:48 PM UTC, whit3rd wrote:
    On Saturday, March 5, 2022 at 5:22:29 PM UTC-8, bill....@ieee.org wrote:
    On Sunday, March 6, 2022 at 10:23:41 AM UTC+11, Sylvia Else wrote:
    I've looked at a number of data sheets, and they never seem to give a voltage rating.

    It seems Coilcraft anticipated your question Sylvia: www.coilcraft.com/getmedia/393e18e1-adbc-45b6-bbe7-5923255e72fc/doc712_Inductor_Voltage_Ratings.pdf

    "Working Voltage Ratings Applied to Inductors"
    "Why Voltage Ratings Are Not Specified on Inductor Data Sheets"

    However I accept someone could have a design that requires
    knowing the wire's dielectric breakdown
    (tested per IEC 60851-5:2008 test 13, documented per IEC 317-0-1, clause 13 ) The wire maker might declare this, but I suppose only in
    special cases would the inductor maker do so.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Allison@21:1/5 to Sylvia Else on Sun Mar 6 15:38:21 2022
    Sylvia Else wrote:
    ===============

    Thanks for the link - I read it all.

    I'd have thought the same issues would arise in the context of mains transformer primaries, though the consequences of failure may be more predictable.


    ** Mains transformers are rated for particular mains supply voltages and frequency.
    Some allowance is made for typical spike voltages but to be safe it it wise to add a 250VAC rated cap cap and/or transient suppressor ( ie Varistor) across that winding.

    The is no similar way for a maker to rate an inductor, as the possible applications are endless.
    Up to the user to figure that out.


    ...... Phil

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Sylvia Else@21:1/5 to Rich S on Mon Mar 7 10:25:54 2022
    On 07-Mar-22 10:05 am, Rich S wrote:
    On Sunday, March 6, 2022 at 9:51:48 PM UTC, whit3rd wrote:
    On Saturday, March 5, 2022 at 5:22:29 PM UTC-8, bill....@ieee.org wrote:
    On Sunday, March 6, 2022 at 10:23:41 AM UTC+11, Sylvia Else wrote:
    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    It seems Coilcraft anticipated your question Sylvia: www.coilcraft.com/getmedia/393e18e1-adbc-45b6-bbe7-5923255e72fc/doc712_Inductor_Voltage_Ratings.pdf

    "Working Voltage Ratings Applied to Inductors"
    "Why Voltage Ratings Are Not Specified on Inductor Data Sheets"

    However I accept someone could have a design that requires
    knowing the wire's dielectric breakdown
    (tested per IEC 60851-5:2008 test 13, documented per IEC 317-0-1, clause 13 )
    The wire maker might declare this, but I suppose only in
    special cases would the inductor maker do so.


    Thanks for the link - I read it all.

    I'd have thought the same issues would arise in the context of mains transformer primaries, though the consequences of failure may be more predictable.

    Sylvia.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Sylvia Else@21:1/5 to jlarkin@highlandsniptechnology.com on Mon Mar 7 19:03:14 2022
    On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    Of course, applying any significant DC voltage across an inductor is
    unlikely to have a good outcome, but one can certainly put a significant >>>> voltage across one for a short period, and it would be nice to know what >>>> the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and
    everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are >>>> close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's
    rare. The dual-winding guys, like DRQ127, are probably bifalar and
    have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good.

    Class D amp?




    No. I was pondering why LED light fittings need to have a large
    electrolytic capacitor with its limited life.

    I have a couple of small LEDs illuminating an otherwise frequently pitch
    black corridor. They're powered through a transformer, bridge rectifier
    and current limiter, with no capacitors at all. They obviously flicker
    at 100Hz, but it's not visible.

    So then I was thinking that one could use a buck converter directly off
    the rectified, but not filtered, mains, hence the voltage requirement.

    This has not moved past musings at this point, but I was looking at the
    voltage specs for inductors, hence my comment.

    Sylvia.

    Lots of LED bulbs have a bridge and a linear IC current limiter but no
    cap. A capless switcher is an interesting idea. The LED could run at
    constant current at a very high duty cycle.

    An inductor like you showed would be fine at hundreds of volts. Test
    one to breakdown!






    Seems to work in LTSpice at least:

    The switch is a stand-in for a digital isolator.

    Apart from V6 which is the incoming mains supply, the various voltage
    sources would be small amounts of power derived from the rectified
    mains. I haven't simulated the fact that this power would not be
    available for short periods.

    Version 4
    SHEET 1 2324 680
    WIRE 112 -400 -800 -400
    WIRE -640 -352 -672 -352
    WIRE -544 -352 -576 -352
    WIRE -368 -352 -544 -352
    WIRE -160 -352 -368 -352
    WIRE -368 -304 -368 -352
    WIRE -160 -272 -160 -352
    WIRE -416 -240 -432 -240
    WIRE 112 -240 112 -400
    WIRE -544 -224 -544 -352
    WIRE -224 -224 -256 -224
    WIRE -672 -192 -672 -352
    WIRE -368 -192 -368 -224
    WIRE -256 -192 -256 -224
    WIRE -256 -192 -368 -192
    WIRE 960 -192 432 -192
    WIRE -368 -160 -368 -192
    WIRE -160 -160 -160 -176
    WIRE 64 -160 -160 -160
    WIRE -160 -144 -160 -160
    WIRE -256 -96 -256 -192
    WIRE -224 -96 -256 -96
    WIRE 112 -80 112 -144
    WIRE 192 -80 112 -80
    WIRE 640 -80 272 -80
    WIRE 800 -80 800 -96
    WIRE 800 -80 640 -80
    WIRE 1184 -80 800 -80
    WIRE 1216 -80 1184 -80
    WIRE -928 -64 -1024 -64
    WIRE -800 -64 -800 -400
    WIRE -800 -64 -864 -64
    WIRE -160 -32 -160 -48
    WIRE 112 -32 112 -80
    WIRE 112 -32 -160 -32
    WIRE -432 -16 -432 -240
    WIRE 304 -16 -432 -16
    WIRE 640 -16 640 -80
    WIRE 800 -16 800 -80
    WIRE -1024 32 -1024 -64
    WIRE -1008 32 -1024 32
    WIRE -928 32 -1008 32
    WIRE -720 32 -864 32
    WIRE 64 32 -64 32
    WIRE 432 32 432 -192
    WIRE 432 32 64 32
    WIRE -544 48 -544 -160
    WIRE -368 48 -368 -80
    WIRE -368 48 -544 48
    WIRE -160 48 -160 -32
    WIRE -160 48 -368 48
    WIRE -64 48 -64 32
    WIRE 432 48 432 32
    WIRE 960 48 960 -192
    WIRE 384 80 336 80
    WIRE 512 80 512 64
    WIRE 512 80 464 80
    WIRE 928 80 512 80
    WIRE 1120 80 1008 80
    WIRE -1024 96 -1024 32
    WIRE 400 112 384 112
    WIRE 640 112 640 48
    WIRE 640 112 464 112
    WIRE 800 112 800 64
    WIRE 928 112 800 112
    WIRE 368 128 352 128
    WIRE 64 144 64 32
    WIRE 80 144 64 144
    WIRE 304 144 304 -16
    WIRE 304 144 240 144
    WIRE 1216 144 1216 -80
    WIRE 32 160 -64 160
    WIRE 416 160 416 144
    WIRE 432 160 432 144
    WIRE 432 160 416 160
    WIRE 448 160 448 144
    WIRE 448 160 432 160
    WIRE 800 160 800 112
    WIRE 448 176 448 160
    WIRE 944 176 944 144
    WIRE 960 176 960 144
    WIRE 960 176 944 176
    WIRE 976 176 976 144
    WIRE 976 176 960 176
    WIRE -160 192 -160 48
    WIRE -64 192 -64 160
    WIRE 32 192 32 160
    WIRE 80 192 32 192
    WIRE -1024 208 -1024 176
    WIRE -928 208 -1024 208
    WIRE -800 208 -800 -64
    WIRE -800 208 -864 208
    WIRE 960 208 960 176
    WIRE 32 224 32 192
    WIRE 640 224 640 112
    WIRE -1024 240 -1024 208
    WIRE -1024 304 -1024 240
    WIRE -928 304 -1024 304
    WIRE -720 304 -720 32
    WIRE -720 304 -864 304
    WIRE 800 304 800 240
    WIRE 32 320 32 288
    WIRE 640 320 640 304
    WIRE 1616 320 1456 320
    WIRE 1856 320 1616 320
    WIRE 1456 352 1456 320
    WIRE 160 368 160 240
    WIRE 240 368 160 368
    WIRE 336 368 336 80
    WIRE 336 368 304 368
    WIRE 1856 368 1856 320
    WIRE -864 400 -1040 400
    WIRE -640 400 -864 400
    WIRE -1040 432 -1040 400
    WIRE 32 432 32 384
    WIRE 160 432 160 368
    WIRE 160 432 32 432
    WIRE 240 432 160 432
    WIRE 1120 432 1120 80
    WIRE 1120 432 304 432
    WIRE -640 448 -640 400
    WIRE 160 448 160 432
    WIRE 1456 480 1456 432
    WIRE 1616 480 1456 480
    WIRE 1856 480 1856 432
    WIRE 1856 480 1616 480
    WIRE -160 528 -160 256
    WIRE -1040 560 -1040 512
    WIRE -880 560 -1040 560
    WIRE -640 560 -640 512
    WIRE -640 560 -880 560
    WIRE 160 560 160 528
    WIRE 176 560 160 560
    FLAG -64 272 0
    FLAG -64 128 0
    FLAG 512 -16 0
    FLAG 448 176 0
    FLAG 160 96 0
    FLAG -672 -112 0
    FLAG -720 304 0
    FLAG 640 320 0
    FLAG 800 304 0
    FLAG 960 208 0
    FLAG 1216 224 0
    FLAG 160 560 0
    FLAG -160 528 0
    FLAG -416 -288 0
    FLAG -1008 32 V6P
    FLAG -1024 240 V6N
    FLAG -880 560 0
    FLAG 1616 480 0
    FLAG 1184 -80 VO
    FLAG -864 400 PI
    FLAG 1616 320 PO
    SYMBOL Digital\\dflop 160 96 R0
    SYMATTR InstName A1
    SYMATTR SpiceLine ref=2.5 VHigh=5 Td=60E-9
    SYMBOL voltage -64 176 R0
    WINDOW 3 24 96 Invisible 2
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR Value PULSE(0 3 0 1E-8 1E-8 9E-6 1E-5 1000000)
    SYMATTR InstName V1
    SYMBOL voltage -64 32 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V2
    SYMATTR Value 5
    SYMBOL voltage 512 80 R180
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V3
    SYMATTR Value 0.5
    SYMBOL Comparators\\LT1711 432 96 M0
    SYMATTR InstName U1
    SYMBOL nmos 64 -240 R0
    SYMATTR InstName M1
    SYMATTR Value BSC42DN25NS3
    SYMBOL ind 288 -96 R90
    WINDOW 0 5 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName L1
    SYMATTR Value 1m
    SYMATTR SpiceLine Ipk=0.7 Rser=1.65 Rpar=175118 Cpar=0 mfg="Bourns,
    Inc." pn="SRR1210-102M"
    SYMBOL cap -560 -224 R0
    SYMATTR InstName C1
    SYMATTR Value 1E-6
    SYMBOL voltage -672 -208 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V5
    SYMATTR Value 8
    SYMBOL diode -640 -336 R270
    WINDOW 0 32 32 VTop 2
    WINDOW 3 0 32 VBottom 2
    SYMATTR InstName D1
    SYMATTR Value 1N914
    SYMATTR Description Schottky diode
    SYMATTR Type schottky
    SYMBOL sw -368 -320 R0
    SYMATTR InstName S1
    SYMATTR Value ""
    SYMATTR SpiceModel MySwitch
    SYMBOL voltage -1024 80 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 24 124 Left 2
    WINDOW 3 -118 55 Left 2
    SYMATTR SpiceLine Rser=0.1
    SYMATTR InstName V6
    SYMATTR Value SINE(0 340 50 0 0 0 2)
    SYMBOL diode -864 48 M270
    WINDOW 0 32 32 VTop 2
    WINDOW 3 0 32 VBottom 2
    SYMATTR InstName D2
    SYMATTR Value RF101L4S
    SYMBOL diode -928 192 M90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName D3
    SYMATTR Value RF101L4S
    SYMBOL diode -928 -80 M90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName D4
    SYMATTR Value RF101L4S
    SYMBOL diode -864 320 M270
    WINDOW 0 32 32 VTop 2
    WINDOW 3 0 32 VBottom 2
    SYMATTR InstName D5
    SYMATTR Value RF101L4S
    SYMBOL cap 624 -16 R0
    WINDOW 0 22 6 Left 2
    SYMATTR InstName C2
    SYMATTR Value 10E-6
    SYMBOL res 624 208 R0
    SYMATTR InstName R1
    SYMATTR Value 1.5
    SYMBOL res 784 -32 R0
    SYMATTR InstName R2
    SYMATTR Value 97900
    SYMBOL res 784 144 R0
    SYMATTR InstName R3
    SYMATTR Value 2000
    SYMBOL Comparators\\LT1711 960 96 R0
    SYMATTR InstName U2
    SYMBOL diode 304 352 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 16 -58 VTop 2
    SYMATTR InstName D6
    SYMATTR Value 1N4148
    SYMBOL diode 304 416 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName D7
    SYMATTR Value 1N4148
    SYMBOL res 1200 128 R0
    SYMATTR InstName R5
    SYMATTR Value 100
    SYMBOL res 144 432 R0
    SYMATTR InstName R4
    SYMATTR Value 10000
    SYMBOL schottky -144 256 R180
    WINDOW 0 24 64 Left 2
    WINDOW 3 24 0 Left 2
    SYMATTR InstName D8
    SYMATTR Value 1N5817
    SYMATTR Description Diode
    SYMATTR Type diode
    SYMBOL Digital\\inv 96 224 R90
    SYMATTR InstName A2
    SYMATTR SpiceLine VHigh=5 ref=2.5
    SYMBOL diode 16 320 R0
    SYMATTR InstName D9
    SYMATTR Value 1N4148
    SYMBOL pnp -224 -48 M180
    SYMATTR InstName Q1
    SYMATTR Value 2N3906
    SYMBOL npn -224 -272 R0
    SYMATTR InstName Q2
    SYMATTR Value 2N2222
    SYMBOL res -384 -176 R0
    SYMATTR InstName R6
    SYMATTR Value 1000
    SYMBOL bi -1040 512 R180
    WINDOW 0 24 80 Left 2
    WINDOW 3 24 0 Left 2
    SYMATTR InstName B1
    SYMATTR Value I=-(V(V6P) - V(V6N)) * I(V6)
    SYMBOL cap -656 448 R0
    SYMATTR InstName C3
    SYMATTR Value 1
    SYMBOL bi 1456 432 R180
    WINDOW 0 24 80 Left 2
    WINDOW 3 24 0 Left 2
    SYMATTR InstName B2
    SYMATTR Value I=V(VO) * I(R5)
    SYMBOL cap 1840 368 R0
    SYMATTR InstName C4
    SYMATTR Value 1
    TEXT -216 416 Left 2 !.tran 0 25E-3 0 1E-8
    TEXT 168 -288 Left 2 !.model MySwitch SW(Ron=.1 Roff=1Meg Vt=2.5 Vh=0.5 Lser=10n Vser=.6)
    TEXT 1704 504 Left 2 !.ic V(PO)=0
    TEXT -1040 616 Left 2 !.ic V(PI)=0

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to All on Mon Mar 7 09:02:54 2022
    On Mon, 7 Mar 2022 19:03:14 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    I've looked at a number of data sheets, and they never seem to give a >>>>> voltage rating.

    Of course, applying any significant DC voltage across an inductor is >>>>> unlikely to have a good outcome, but one can certainly put a significant >>>>> voltage across one for a short period, and it would be nice to know what >>>>> the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and >>>> everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the >>>>> wire and the core, and between windings at the two ends where they are >>>>> close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's
    rare. The dual-winding guys, like DRQ127, are probably bifalar and
    have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good.

    Class D amp?




    No. I was pondering why LED light fittings need to have a large
    electrolytic capacitor with its limited life.

    I have a couple of small LEDs illuminating an otherwise frequently pitch >>> black corridor. They're powered through a transformer, bridge rectifier
    and current limiter, with no capacitors at all. They obviously flicker
    at 100Hz, but it's not visible.

    So then I was thinking that one could use a buck converter directly off
    the rectified, but not filtered, mains, hence the voltage requirement.

    This has not moved past musings at this point, but I was looking at the
    voltage specs for inductors, hence my comment.

    Sylvia.

    Lots of LED bulbs have a bridge and a linear IC current limiter but no
    cap. A capless switcher is an interesting idea. The LED could run at
    constant current at a very high duty cycle.

    An inductor like you showed would be fine at hundreds of volts. Test
    one to breakdown!






    Seems to work in LTSpice at least:

    The switch is a stand-in for a digital isolator.

    Apart from V6 which is the incoming mains supply, the various voltage
    sources would be small amounts of power derived from the rectified
    mains. I haven't simulated the fact that this power would not be
    available for short periods.

    <snip>

    LTspice IV threw a 'singular matrix node error' here, but only if
    the Philips models for 2N2222 and 2N3906 were used. NSC models
    allowed the simulation to run.

    I'm not sure that you're going to find a 'digital isolator' that's
    designed for PWM - they're usually pretty slow. You might consider
    an integrated gate driver + discrete nmos as a lower-parts-count
    solution.

    If you check the input current, or the current in the freewheeling
    diode (probably not included inside the digital isolator, by the way),
    you'll see diode current spikes occurring when it turns off and the
    switch turns on. The amplitude of these spikes will vary with diode
    type and nmos switching speed (slower speeds are generated if a
    series gate resistor is present on M1).

    These spikes are not simulation artifacts, they are modeling attempts
    to simulate schottky capacitance or rectifier reverse recovery.
    200V schottkeys are rare beasts, but there are fast recovery
    rectifiers offered in the standard LTspice distribution selection
    lists.

    The Bourns data sheet gives a flux density calculation in gauss
    using K * L * dI with a frequency-dependent core loss chart
    specific to the SRR1210 series.

    In a ripple-regulated circuit dI will vary with frequency - in
    the sim it's between 200 and 400mAppk.


    In a regulated circuit, the peak to peak flux swing in the choke is
    determined by Bppk = V * t / ( N * A)
    where
    Bppk = peak to peak flux density (Teslas)
    V = Vout + Vdfreewheel (volts)
    t = Tfreewheel (seconds)
    N = number of turns on the choke
    A = xsectional area of choke

    If you've got a table for the choke's material, you can work
    out core loss (W/m^3 - mW/cm^3) and apply that to the volume
    of the core geometry being used.

    Voltage is present in that equation. For peak or surge, it's
    either saturation or turn/terminal breakdown limited. Some
    core structures, when impressed with low impedance surges,
    will try to turn themselves inside out, in the attempt to
    force changes in the magnetic length/area ratio.

    Lighting ballast design for the domestic market is not the easiest
    road to fame and fortune.

    Considering the efficiencies of LED sources and the dominance
    of standard hardware formats, it turns into a marketing exercise.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to All on Mon Mar 7 09:10:30 2022
    On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    Of course, applying any significant DC voltage across an inductor is
    unlikely to have a good outcome, but one can certainly put a significant >>> voltage across one for a short period, and it would be nice to know what >>> the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and
    everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are
    close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's
    rare. The dual-winding guys, like DRQ127, are probably bifalar and
    have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good.

    Class D amp?




    No. I was pondering why LED light fittings need to have a large
    electrolytic capacitor with its limited life.

    I have a couple of small LEDs illuminating an otherwise frequently pitch >black corridor. They're powered through a transformer, bridge rectifier
    and current limiter, with no capacitors at all. They obviously flicker
    at 100Hz, but it's not visible.

    So then I was thinking that one could use a buck converter directly off
    the rectified, but not filtered, mains, hence the voltage requirement.

    This has not moved past musings at this point, but I was looking at the >voltage specs for inductors, hence my comment.

    Sylvia.

    In any event, new luminaires do tend to try to build into the hardware
    any type of ballasting and safety barrier that may be required for
    direct sale.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From LM@21:1/5 to All on Mon Mar 7 20:31:03 2022
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    Of course, applying any significant DC voltage across an inductor is
    unlikely to have a good outcome, but one can certainly put a significant >voltage across one for a short period, and it would be nice to know what
    the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are
    close together.

    Sylvia.
    Voltage rating can be complicated. For instance, to be CE compliant, Transformer/Coil needs two different insulators between mains (230V
    AC) and low voltage side. And so on. I have noticed that there is
    usually a reason for those rules, but they are not very obvious and
    don't come by accident. And then there is China Export standards.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Walliker@21:1/5 to All on Mon Mar 7 13:07:32 2022
    On Monday, 7 March 2022 at 18:31:20 UTC, LM wrote:

    Voltage rating can be complicated. For instance, to be CE compliant, Transformer/Coil needs two different insulators between mains (230V
    AC) and low voltage side. And so on. I have noticed that there is
    usually a reason for those rules, but they are not very obvious and
    don't come by accident. And then there is China Export standards.

    Two different insulators or one thicker one called "reinforced insulation"
    if its a class 2 (double insulated) product.

    John

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Allison@21:1/5 to All on Mon Mar 7 13:46:26 2022
    LM wrote:
    ------------------

    Voltage rating can be complicated. For instance, to be CE compliant, Transformer/Coil needs two different insulators between mains (230V
    AC) and low voltage side.


    ** Not just " different" but must be ones specified in the relevant standard.

    The enamel coating on copper wire is the first, the second needs to be a non hygroscopic, high softening temp insulator with good stability over decades. Various plastics comply as does fiber sheet and treated cardboard.

    I have noticed that there is usually a reason for those rules, but they are not very obvious and
    don't come by accident.

    ** Correct - they are the result of hard won experience.

    And then there is China Export standards.

    ** The rules there is to do whatever you can get away with.


    ....... Phil

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Lasse Langwadt Christensen@21:1/5 to All on Mon Mar 7 13:56:50 2022
    mandag den 7. marts 2022 kl. 22.46.34 UTC+1 skrev palli...@gmail.com:
    LM wrote:
    ------------------

    Voltage rating can be complicated. For instance, to be CE compliant, Transformer/Coil needs two different insulators between mains (230V
    AC) and low voltage side.

    ** Not just " different" but must be ones specified in the relevant standard.

    The enamel coating on copper wire is the first, the second needs to be a non hygroscopic, high softening temp insulator with good stability over decades. Various plastics comply as does fiber sheet and treated cardboard.
    I have noticed that there is usually a reason for those rules, but they are not very obvious and
    don't come by accident.
    ** Correct - they are the result of hard won experience.
    And then there is China Export standards.
    ** The rules there is to do whatever you can get away with.

    as an example: https://youtu.be/w-p3GXXFfQw?t=688

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Sylvia Else@21:1/5 to legg on Tue Mar 8 09:41:51 2022
    On 08-Mar-22 1:02 am, legg wrote:
    On Mon, 7 Mar 2022 19:03:14 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid> >>>>> wrote:

    I've looked at a number of data sheets, and they never seem to give a >>>>>> voltage rating.

    Of course, applying any significant DC voltage across an inductor is >>>>>> unlikely to have a good outcome, but one can certainly put a significant >>>>>> voltage across one for a short period, and it would be nice to know what >>>>>> the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and >>>>> everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the >>>>>> wire and the core, and between windings at the two ends where they are >>>>>> close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's
    rare. The dual-winding guys, like DRQ127, are probably bifalar and
    have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good. >>>>>
    Class D amp?




    No. I was pondering why LED light fittings need to have a large
    electrolytic capacitor with its limited life.

    I have a couple of small LEDs illuminating an otherwise frequently pitch >>>> black corridor. They're powered through a transformer, bridge rectifier >>>> and current limiter, with no capacitors at all. They obviously flicker >>>> at 100Hz, but it's not visible.

    So then I was thinking that one could use a buck converter directly off >>>> the rectified, but not filtered, mains, hence the voltage requirement. >>>>
    This has not moved past musings at this point, but I was looking at the >>>> voltage specs for inductors, hence my comment.

    Sylvia.

    Lots of LED bulbs have a bridge and a linear IC current limiter but no
    cap. A capless switcher is an interesting idea. The LED could run at
    constant current at a very high duty cycle.

    An inductor like you showed would be fine at hundreds of volts. Test
    one to breakdown!






    Seems to work in LTSpice at least:

    The switch is a stand-in for a digital isolator.

    Apart from V6 which is the incoming mains supply, the various voltage
    sources would be small amounts of power derived from the rectified
    mains. I haven't simulated the fact that this power would not be
    available for short periods.

    <snip>

    LTspice IV threw a 'singular matrix node error' here, but only if
    the Philips models for 2N2222 and 2N3906 were used. NSC models
    allowed the simulation to run.

    I'm not sure that you're going to find a 'digital isolator' that's
    designed for PWM - they're usually pretty slow. You might consider
    an integrated gate driver + discrete nmos as a lower-parts-count
    solution.

    If you check the input current, or the current in the freewheeling
    diode (probably not included inside the digital isolator, by the way),
    you'll see diode current spikes occurring when it turns off and the
    switch turns on. The amplitude of these spikes will vary with diode
    type and nmos switching speed (slower speeds are generated if a
    series gate resistor is present on M1).

    These spikes are not simulation artifacts, they are modeling attempts
    to simulate schottky capacitance or rectifier reverse recovery.
    200V schottkeys are rare beasts, but there are fast recovery
    rectifiers offered in the standard LTspice distribution selection
    lists.

    The Bourns data sheet gives a flux density calculation in gauss
    using K * L * dI with a frequency-dependent core loss chart
    specific to the SRR1210 series.

    In a ripple-regulated circuit dI will vary with frequency - in
    the sim it's between 200 and 400mAppk.


    In a regulated circuit, the peak to peak flux swing in the choke is determined by Bppk = V * t / ( N * A)
    where
    Bppk = peak to peak flux density (Teslas)
    V = Vout + Vdfreewheel (volts)
    t = Tfreewheel (seconds)
    N = number of turns on the choke
    A = xsectional area of choke

    If you've got a table for the choke's material, you can work
    out core loss (W/m^3 - mW/cm^3) and apply that to the volume
    of the core geometry being used.

    Voltage is present in that equation. For peak or surge, it's
    either saturation or turn/terminal breakdown limited. Some
    core structures, when impressed with low impedance surges,
    will try to turn themselves inside out, in the attempt to
    force changes in the magnetic length/area ratio.

    Lighting ballast design for the domestic market is not the easiest
    road to fame and fortune.

    Considering the efficiencies of LED sources and the dominance
    of standard hardware formats, it turns into a marketing exercise.

    RL

    Thanks for taking a look. In the end this was never going to be more
    than an academic exercise. I don't even intend to attempt to build one.
    To be remotely viable commercially, most of the electronics would have
    to be bundled into an IC, and I don't see that happening.

    While eliminating the electrolytic capacitor could benefit the consumer (assuming the high voltages don't produce other reductions in life),
    it's of little interest to manufacturers - even those making the
    hypothetical IC.

    Sylvia.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to All on Mon Mar 7 20:11:59 2022
    On Tue, 8 Mar 2022 09:41:51 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 08-Mar-22 1:02 am, legg wrote:
    On Mon, 7 Mar 2022 19:03:14 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid> >>>>>> wrote:

    I've looked at a number of data sheets, and they never seem to give a >>>>>>> voltage rating.

    Of course, applying any significant DC voltage across an inductor is >>>>>>> unlikely to have a good outcome, but one can certainly put a significant
    voltage across one for a short period, and it would be nice to know what
    the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and >>>>>> everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the >>>>>>> wire and the core, and between windings at the two ends where they are >>>>>>> close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's >>>>>> rare. The dual-winding guys, like DRQ127, are probably bifalar and >>>>>> have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good. >>>>>>
    Class D amp?




    No. I was pondering why LED light fittings need to have a large
    electrolytic capacitor with its limited life.

    I have a couple of small LEDs illuminating an otherwise frequently pitch >>>>> black corridor. They're powered through a transformer, bridge rectifier >>>>> and current limiter, with no capacitors at all. They obviously flicker >>>>> at 100Hz, but it's not visible.

    So then I was thinking that one could use a buck converter directly off >>>>> the rectified, but not filtered, mains, hence the voltage requirement. >>>>>
    This has not moved past musings at this point, but I was looking at the >>>>> voltage specs for inductors, hence my comment.

    Sylvia.

    Lots of LED bulbs have a bridge and a linear IC current limiter but no >>>> cap. A capless switcher is an interesting idea. The LED could run at
    constant current at a very high duty cycle.

    An inductor like you showed would be fine at hundreds of volts. Test
    one to breakdown!






    Seems to work in LTSpice at least:

    The switch is a stand-in for a digital isolator.

    Apart from V6 which is the incoming mains supply, the various voltage
    sources would be small amounts of power derived from the rectified
    mains. I haven't simulated the fact that this power would not be
    available for short periods.

    <snip>

    LTspice IV threw a 'singular matrix node error' here, but only if
    the Philips models for 2N2222 and 2N3906 were used. NSC models
    allowed the simulation to run.

    I'm not sure that you're going to find a 'digital isolator' that's
    designed for PWM - they're usually pretty slow. You might consider
    an integrated gate driver + discrete nmos as a lower-parts-count
    solution.

    If you check the input current, or the current in the freewheeling
    diode (probably not included inside the digital isolator, by the way),
    you'll see diode current spikes occurring when it turns off and the
    switch turns on. The amplitude of these spikes will vary with diode
    type and nmos switching speed (slower speeds are generated if a
    series gate resistor is present on M1).

    These spikes are not simulation artifacts, they are modeling attempts
    to simulate schottky capacitance or rectifier reverse recovery.
    200V schottkeys are rare beasts, but there are fast recovery
    rectifiers offered in the standard LTspice distribution selection
    lists.

    The Bourns data sheet gives a flux density calculation in gauss
    using K * L * dI with a frequency-dependent core loss chart
    specific to the SRR1210 series.

    In a ripple-regulated circuit dI will vary with frequency - in
    the sim it's between 200 and 400mAppk.


    In a regulated circuit, the peak to peak flux swing in the choke is
    determined by Bppk = V * t / ( N * A)
    where
    Bppk = peak to peak flux density (Teslas)
    V = Vout + Vdfreewheel (volts)
    t = Tfreewheel (seconds)
    N = number of turns on the choke
    A = xsectional area of choke

    If you've got a table for the choke's material, you can work
    out core loss (W/m^3 - mW/cm^3) and apply that to the volume
    of the core geometry being used.

    Voltage is present in that equation. For peak or surge, it's
    either saturation or turn/terminal breakdown limited. Some
    core structures, when impressed with low impedance surges,
    will try to turn themselves inside out, in the attempt to
    force changes in the magnetic length/area ratio.

    Lighting ballast design for the domestic market is not the easiest
    road to fame and fortune.

    Considering the efficiencies of LED sources and the dominance
    of standard hardware formats, it turns into a marketing exercise.

    RL

    Thanks for taking a look. In the end this was never going to be more
    than an academic exercise. I don't even intend to attempt to build one.
    To be remotely viable commercially, most of the electronics would have
    to be bundled into an IC, and I don't see that happening.

    While eliminating the electrolytic capacitor could benefit the consumer >(assuming the high voltages don't produce other reductions in life),
    it's of little interest to manufacturers - even those making the
    hypothetical IC.

    Sylvia.

    Well, they wouldn't tell you, if they were, but there ARE application-
    specific ICs showing up in SEA - they just don't crow about it, or
    have any interest in the North American market.

    That flat-topped line current waveform isn't any easier, w/r to
    harmonic distortion on the transformer-coupled grid, than the
    capacitive rectifier peak, but it is 'loss-reduced'. The linear
    LED lamps have a similar profile, when caps are removed.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Larkin@21:1/5 to All on Mon Mar 7 17:20:22 2022
    On Tue, 8 Mar 2022 09:41:51 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 08-Mar-22 1:02 am, legg wrote:
    On Mon, 7 Mar 2022 19:03:14 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid> >>>>>> wrote:

    I've looked at a number of data sheets, and they never seem to give a >>>>>>> voltage rating.

    Of course, applying any significant DC voltage across an inductor is >>>>>>> unlikely to have a good outcome, but one can certainly put a significant
    voltage across one for a short period, and it would be nice to know what
    the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and >>>>>> everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the >>>>>>> wire and the core, and between windings at the two ends where they are >>>>>>> close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's >>>>>> rare. The dual-winding guys, like DRQ127, are probably bifalar and >>>>>> have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good. >>>>>>
    Class D amp?




    No. I was pondering why LED light fittings need to have a large
    electrolytic capacitor with its limited life.

    I have a couple of small LEDs illuminating an otherwise frequently pitch >>>>> black corridor. They're powered through a transformer, bridge rectifier >>>>> and current limiter, with no capacitors at all. They obviously flicker >>>>> at 100Hz, but it's not visible.

    So then I was thinking that one could use a buck converter directly off >>>>> the rectified, but not filtered, mains, hence the voltage requirement. >>>>>
    This has not moved past musings at this point, but I was looking at the >>>>> voltage specs for inductors, hence my comment.

    Sylvia.

    Lots of LED bulbs have a bridge and a linear IC current limiter but no >>>> cap. A capless switcher is an interesting idea. The LED could run at
    constant current at a very high duty cycle.

    An inductor like you showed would be fine at hundreds of volts. Test
    one to breakdown!






    Seems to work in LTSpice at least:

    The switch is a stand-in for a digital isolator.

    Apart from V6 which is the incoming mains supply, the various voltage
    sources would be small amounts of power derived from the rectified
    mains. I haven't simulated the fact that this power would not be
    available for short periods.

    <snip>

    LTspice IV threw a 'singular matrix node error' here, but only if
    the Philips models for 2N2222 and 2N3906 were used. NSC models
    allowed the simulation to run.

    I'm not sure that you're going to find a 'digital isolator' that's
    designed for PWM - they're usually pretty slow. You might consider
    an integrated gate driver + discrete nmos as a lower-parts-count
    solution.

    If you check the input current, or the current in the freewheeling
    diode (probably not included inside the digital isolator, by the way),
    you'll see diode current spikes occurring when it turns off and the
    switch turns on. The amplitude of these spikes will vary with diode
    type and nmos switching speed (slower speeds are generated if a
    series gate resistor is present on M1).

    These spikes are not simulation artifacts, they are modeling attempts
    to simulate schottky capacitance or rectifier reverse recovery.
    200V schottkeys are rare beasts, but there are fast recovery
    rectifiers offered in the standard LTspice distribution selection
    lists.

    The Bourns data sheet gives a flux density calculation in gauss
    using K * L * dI with a frequency-dependent core loss chart
    specific to the SRR1210 series.

    In a ripple-regulated circuit dI will vary with frequency - in
    the sim it's between 200 and 400mAppk.


    In a regulated circuit, the peak to peak flux swing in the choke is
    determined by Bppk = V * t / ( N * A)
    where
    Bppk = peak to peak flux density (Teslas)
    V = Vout + Vdfreewheel (volts)
    t = Tfreewheel (seconds)
    N = number of turns on the choke
    A = xsectional area of choke

    If you've got a table for the choke's material, you can work
    out core loss (W/m^3 - mW/cm^3) and apply that to the volume
    of the core geometry being used.

    Voltage is present in that equation. For peak or surge, it's
    either saturation or turn/terminal breakdown limited. Some
    core structures, when impressed with low impedance surges,
    will try to turn themselves inside out, in the attempt to
    force changes in the magnetic length/area ratio.

    Lighting ballast design for the domestic market is not the easiest
    road to fame and fortune.

    Considering the efficiencies of LED sources and the dominance
    of standard hardware formats, it turns into a marketing exercise.

    RL

    Thanks for taking a look. In the end this was never going to be more
    than an academic exercise. I don't even intend to attempt to build one.
    To be remotely viable commercially, most of the electronics would have
    to be bundled into an IC, and I don't see that happening.

    The real challenge would be to do it with 12 cents worth of discrete
    parts.

    --

    If a man will begin with certainties, he shall end with doubts,
    but if he will be content to begin with doubts he shall end in certainties. Francis Bacon

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Sylvia Else@21:1/5 to legg on Tue Mar 8 13:13:12 2022
    On 08-Mar-22 12:11 pm, legg wrote:
    On Tue, 8 Mar 2022 09:41:51 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 08-Mar-22 1:02 am, legg wrote:
    On Mon, 7 Mar 2022 19:03:14 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid> >>>>> wrote:

    On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid> >>>>>>> wrote:

    I've looked at a number of data sheets, and they never seem to give a >>>>>>>> voltage rating.

    Of course, applying any significant DC voltage across an inductor is >>>>>>>> unlikely to have a good outcome, but one can certainly put a significant
    voltage across one for a short period, and it would be nice to know what
    the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and >>>>>>> everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the >>>>>>>> wire and the core, and between windings at the two ends where they are >>>>>>>> close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's >>>>>>> rare. The dual-winding guys, like DRQ127, are probably bifalar and >>>>>>> have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good. >>>>>>>
    Class D amp?




    No. I was pondering why LED light fittings need to have a large
    electrolytic capacitor with its limited life.

    I have a couple of small LEDs illuminating an otherwise frequently pitch >>>>>> black corridor. They're powered through a transformer, bridge rectifier >>>>>> and current limiter, with no capacitors at all. They obviously flicker >>>>>> at 100Hz, but it's not visible.

    So then I was thinking that one could use a buck converter directly off >>>>>> the rectified, but not filtered, mains, hence the voltage requirement. >>>>>>
    This has not moved past musings at this point, but I was looking at the >>>>>> voltage specs for inductors, hence my comment.

    Sylvia.

    Lots of LED bulbs have a bridge and a linear IC current limiter but no >>>>> cap. A capless switcher is an interesting idea. The LED could run at >>>>> constant current at a very high duty cycle.

    An inductor like you showed would be fine at hundreds of volts. Test >>>>> one to breakdown!






    Seems to work in LTSpice at least:

    The switch is a stand-in for a digital isolator.

    Apart from V6 which is the incoming mains supply, the various voltage
    sources would be small amounts of power derived from the rectified
    mains. I haven't simulated the fact that this power would not be
    available for short periods.

    <snip>

    LTspice IV threw a 'singular matrix node error' here, but only if
    the Philips models for 2N2222 and 2N3906 were used. NSC models
    allowed the simulation to run.

    I'm not sure that you're going to find a 'digital isolator' that's
    designed for PWM - they're usually pretty slow. You might consider
    an integrated gate driver + discrete nmos as a lower-parts-count
    solution.

    If you check the input current, or the current in the freewheeling
    diode (probably not included inside the digital isolator, by the way),
    you'll see diode current spikes occurring when it turns off and the
    switch turns on. The amplitude of these spikes will vary with diode
    type and nmos switching speed (slower speeds are generated if a
    series gate resistor is present on M1).

    These spikes are not simulation artifacts, they are modeling attempts
    to simulate schottky capacitance or rectifier reverse recovery.
    200V schottkeys are rare beasts, but there are fast recovery
    rectifiers offered in the standard LTspice distribution selection
    lists.

    The Bourns data sheet gives a flux density calculation in gauss
    using K * L * dI with a frequency-dependent core loss chart
    specific to the SRR1210 series.

    In a ripple-regulated circuit dI will vary with frequency - in
    the sim it's between 200 and 400mAppk.


    In a regulated circuit, the peak to peak flux swing in the choke is
    determined by Bppk = V * t / ( N * A)
    where
    Bppk = peak to peak flux density (Teslas)
    V = Vout + Vdfreewheel (volts)
    t = Tfreewheel (seconds)
    N = number of turns on the choke
    A = xsectional area of choke

    If you've got a table for the choke's material, you can work
    out core loss (W/m^3 - mW/cm^3) and apply that to the volume
    of the core geometry being used.

    Voltage is present in that equation. For peak or surge, it's
    either saturation or turn/terminal breakdown limited. Some
    core structures, when impressed with low impedance surges,
    will try to turn themselves inside out, in the attempt to
    force changes in the magnetic length/area ratio.

    Lighting ballast design for the domestic market is not the easiest
    road to fame and fortune.

    Considering the efficiencies of LED sources and the dominance
    of standard hardware formats, it turns into a marketing exercise.

    RL

    Thanks for taking a look. In the end this was never going to be more
    than an academic exercise. I don't even intend to attempt to build one.
    To be remotely viable commercially, most of the electronics would have
    to be bundled into an IC, and I don't see that happening.

    While eliminating the electrolytic capacitor could benefit the consumer
    (assuming the high voltages don't produce other reductions in life),
    it's of little interest to manufacturers - even those making the
    hypothetical IC.

    Sylvia.

    Well, they wouldn't tell you, if they were, but there ARE application- specific ICs showing up in SEA - they just don't crow about it, or
    have any interest in the North American market.

    That flat-topped line current waveform isn't any easier, w/r to
    harmonic distortion on the transformer-coupled grid, than the
    capacitive rectifier peak, but it is 'loss-reduced'. The linear
    LED lamps have a similar profile, when caps are removed.

    RL

    My own home is illuminated almost entirely by low voltage lamps.
    Probably someone in the past fell for the notion that low voltage means
    low power consumption.

    I replaced all the previous incandescent low voltage lamps with low
    voltage LEDs with the same fitting. When the caps wear out, which is
    within a few years, they start flashing. Next time it happens, I'll try removing the caps entirely. I'm not that hopeful, but you never know.

    Sylvia.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to legg@nospam.magma.ca on Tue Mar 8 07:52:05 2022
    On a sunny day (Mon, 07 Mar 2022 20:11:59 -0500) it happened legg <legg@nospam.magma.ca> wrote in <uuad2hpo887r2jdban5a8mghujpq5md96t@4ax.com>:

    That flat-topped line current waveform isn't any easier, w/r to
    harmonic distortion on the transformer-coupled grid, than the
    capacitive rectifier peak, but it is 'loss-reduced'. The linear
    LED lamps have a similar profile, when caps are removed.

    RL

    The Chinese LED lamps from ebay I have use a much smaller electrolytic capacitor that you could probably leave out:
    circuit:
    http://panteltje.com/pub/LED_light_circuit_diagram_IMG_6925.JPG

    A look inside :
    http://panteltje.com/pub/LED_light_fix_IMG_6918.JPG
    The current is limited by the 1 uF cap in series with the AC.
    The voltage on the eletrolytics is limited by the LEDs working as zeners.

    simple...
    Some LEDs died
    Transients on the mains commom here.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to jlarkin@highland_atwork_technology. on Tue Mar 8 07:36:19 2022
    On Mon, 07 Mar 2022 17:20:22 -0800, John Larkin <jlarkin@highland_atwork_technology.com> wrote:

    On Tue, 8 Mar 2022 09:41:51 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 08-Mar-22 1:02 am, legg wrote:
    On Mon, 7 Mar 2022 19:03:14 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 06-Mar-22 2:12 pm, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 12:21:09 +1100, Sylvia Else <sylvia@email.invalid> >>>>> wrote:

    On 06-Mar-22 10:59 am, jlarkin@highlandsniptechnology.com wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid> >>>>>>> wrote:

    I've looked at a number of data sheets, and they never seem to give a >>>>>>>> voltage rating.

    Of course, applying any significant DC voltage across an inductor is >>>>>>>> unlikely to have a good outcome, but one can certainly put a significant
    voltage across one for a short period, and it would be nice to know what
    the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    Powdered iron can get lossy if you drive it hard. Then it gets hot and >>>>>>> everything gets worse. KoolMu or Sendust has become affordable.


    The obvious concerns here are breakdown of the insulation between the >>>>>>>> wire and the core, and between windings at the two ends where they are >>>>>>>> close together.

    Sylvia.

    I think a few of the Coilcraft parts have voltage ratings, but it's >>>>>>> rare. The dual-winding guys, like DRQ127, are probably bifalar and >>>>>>> have more ways to arc.

    I usually test them.

    How much voltage were you considering? That toroid looks pretty good. >>>>>>>
    Class D amp?




    No. I was pondering why LED light fittings need to have a large
    electrolytic capacitor with its limited life.

    I have a couple of small LEDs illuminating an otherwise frequently pitch >>>>>> black corridor. They're powered through a transformer, bridge rectifier >>>>>> and current limiter, with no capacitors at all. They obviously flicker >>>>>> at 100Hz, but it's not visible.

    So then I was thinking that one could use a buck converter directly off >>>>>> the rectified, but not filtered, mains, hence the voltage requirement. >>>>>>
    This has not moved past musings at this point, but I was looking at the >>>>>> voltage specs for inductors, hence my comment.

    Sylvia.

    Lots of LED bulbs have a bridge and a linear IC current limiter but no >>>>> cap. A capless switcher is an interesting idea. The LED could run at >>>>> constant current at a very high duty cycle.

    An inductor like you showed would be fine at hundreds of volts. Test >>>>> one to breakdown!






    Seems to work in LTSpice at least:

    The switch is a stand-in for a digital isolator.

    Apart from V6 which is the incoming mains supply, the various voltage
    sources would be small amounts of power derived from the rectified
    mains. I haven't simulated the fact that this power would not be
    available for short periods.

    <snip>

    LTspice IV threw a 'singular matrix node error' here, but only if
    the Philips models for 2N2222 and 2N3906 were used. NSC models
    allowed the simulation to run.

    I'm not sure that you're going to find a 'digital isolator' that's
    designed for PWM - they're usually pretty slow. You might consider
    an integrated gate driver + discrete nmos as a lower-parts-count
    solution.

    If you check the input current, or the current in the freewheeling
    diode (probably not included inside the digital isolator, by the way),
    you'll see diode current spikes occurring when it turns off and the
    switch turns on. The amplitude of these spikes will vary with diode
    type and nmos switching speed (slower speeds are generated if a
    series gate resistor is present on M1).

    These spikes are not simulation artifacts, they are modeling attempts
    to simulate schottky capacitance or rectifier reverse recovery.
    200V schottkeys are rare beasts, but there are fast recovery
    rectifiers offered in the standard LTspice distribution selection
    lists.

    The Bourns data sheet gives a flux density calculation in gauss
    using K * L * dI with a frequency-dependent core loss chart
    specific to the SRR1210 series.

    In a ripple-regulated circuit dI will vary with frequency - in
    the sim it's between 200 and 400mAppk.


    In a regulated circuit, the peak to peak flux swing in the choke is
    determined by Bppk = V * t / ( N * A)
    where
    Bppk = peak to peak flux density (Teslas)
    V = Vout + Vdfreewheel (volts)
    t = Tfreewheel (seconds)
    N = number of turns on the choke
    A = xsectional area of choke

    If you've got a table for the choke's material, you can work
    out core loss (W/m^3 - mW/cm^3) and apply that to the volume
    of the core geometry being used.

    Voltage is present in that equation. For peak or surge, it's
    either saturation or turn/terminal breakdown limited. Some
    core structures, when impressed with low impedance surges,
    will try to turn themselves inside out, in the attempt to
    force changes in the magnetic length/area ratio.

    Lighting ballast design for the domestic market is not the easiest
    road to fame and fortune.

    Considering the efficiencies of LED sources and the dominance
    of standard hardware formats, it turns into a marketing exercise.

    RL

    Thanks for taking a look. In the end this was never going to be more
    than an academic exercise. I don't even intend to attempt to build one.
    To be remotely viable commercially, most of the electronics would have
    to be bundled into an IC, and I don't see that happening.

    The real challenge would be to do it with 12 cents worth of discrete
    parts.

    You might be surprised. I recall being totally demoralized by an
    0.08 transformer quote in 2008. If you stick to the right commodity
    materials, it's a completely different market, or perhaps the
    demoralization was intentional. I'm being paranoid here.

    I visualize being paid to use parts, under corporate, tax or political circumstances, that I'd really rather not consider . . .

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Skittles@21:1/5 to All on Tue Mar 8 09:07:34 2022
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    Of course, applying any significant DC voltage across an inductor is
    unlikely to have a good outcome, but one can certainly put a significant >voltage across one for a short period, and it would be nice to know what
    the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are
    close together.

    Sylvia.


    If your inductor has a decent Q value (low resistance) then the DC
    voltage drop across the inductor is almost zero. Should be no DC
    arcing within the inductor itself.

    Skittles

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Sylvia Else@21:1/5 to Skittles on Wed Mar 9 09:42:44 2022
    On 09-Mar-22 3:07 am, Skittles wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    Of course, applying any significant DC voltage across an inductor is
    unlikely to have a good outcome, but one can certainly put a significant
    voltage across one for a short period, and it would be nice to know what
    the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are
    close together.

    Sylvia.


    If your inductor has a decent Q value (low resistance) then the DC
    voltage drop across the inductor is almost zero. Should be no DC
    arcing within the inductor itself.

    Skittles

    Yes. The issue related to short pulses.

    Sylvia.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Skittles@21:1/5 to All on Tue Mar 8 20:54:50 2022
    On Wed, 9 Mar 2022 09:42:44 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 09-Mar-22 3:07 am, Skittles wrote:
    On Sun, 6 Mar 2022 10:23:29 +1100, Sylvia Else <sylvia@email.invalid>
    wrote:

    I've looked at a number of data sheets, and they never seem to give a
    voltage rating.

    Of course, applying any significant DC voltage across an inductor is
    unlikely to have a good outcome, but one can certainly put a significant >>> voltage across one for a short period, and it would be nice to know what >>> the limits are.

    As a random example

    https://www.farnell.com/datasheets/1870387.pdf

    The obvious concerns here are breakdown of the insulation between the
    wire and the core, and between windings at the two ends where they are
    close together.

    Sylvia.


    If your inductor has a decent Q value (low resistance) then the DC
    voltage drop across the inductor is almost zero. Should be no DC
    arcing within the inductor itself.

    Skittles

    Yes. The issue related to short pulses.

    Sylvia.

    https://www.coilcraft.com/getmedia/393e18e1-adbc-45b6-bbe7-5923255e72fc/doc712_Inductor_Voltage_Ratings.pdf


    https://www.coilcraft.com/getmedia/1ce5c5e9-3266-4dfa-80a3-e085d659785e/doc1520_operating_voltage_ratings_for_inductors.pdf

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)