No voltage rating for inductors...

[Sylvia Else]

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.

 

[server]

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

 

[Sylvia Else]

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.

 

[Anthony William Sloman]

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

 

[Anthony William Sloman]

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

 

[server]

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

 

[legg]

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

 

[whit3rd]

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...

 

[Rich S]

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.

 

[Sylvia Else]

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.

 

[Phil Allison]

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

 

[Sylvia Else]

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
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SYMBOL voltage -64 176 R0
WINDOW 3 24 96 Invisible 2
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SYMATTR Value PULSE(0 3 0 1E-8 1E-8 9E-6 1E-5 1000000)
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SYMATTR Value BSC42DN25NS3
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WINDOW 0 5 56 VBottom 2
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SYMATTR Value RF101L4S
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SYMATTR Value 10E-6
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SYMATTR Value 1.5
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SYMATTR Value 97900
SYMBOL res 784 144 R0
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SYMATTR Value 2000
SYMBOL Comparators\\\\LT1711 960 96 R0
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SYMBOL diode 304 352 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 16 -58 VTop 2
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SYMATTR Value 1N4148
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SYMATTR Value 10000
SYMBOL schottky -144 256 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
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SYMATTR Type diode
SYMBOL Digital\\\\inv 96 224 R90
SYMATTR InstName A2
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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
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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

 

[legg]

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

 

[legg]

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

 

[LM]

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.

 

[John Walliker]

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

 

[Phil Allison]

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

 

[Lasse Langwadt Christensen]

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

 

[Sylvia Else]

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.

 

[legg]

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