Bifilar inductor?

[George Herold]

Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)
My question is; how the heck does that do anything inductive?

George H.

 

[John Larkin]

On Thu, 4 Jan 2018 11:37:19 -0800 (PST), George Herold
<gherold@teachspin.com> wrote:

Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)
My question is; how the heck does that do anything inductive?

George H.

I refuse to watch Squeaky's videos.

A bifilar inductor is really a 1:1 transformer with both windings made
at once from a twisted pair. So it has very low leakage inductance and
lots of inter-winding capacitance.

https://www.digikey.com/product-detail/en/eaton/DRQ127-3R3-R/513-1308-2-ND/667268

These are sometimes sold as transformers, sometimes as dual-winding
inductors. They are inductors in the sense that the winding inductance
is specified, with a tolerance.

I love those DRQ-series gadgets. They are good for all sorts of
things.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[George Herold]

On Thursday, January 4, 2018 at 7:42:34 PM UTC-5, John Larkin wrote:

On Thu, 4 Jan 2018 11:37:19 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)
My question is; how the heck does that do anything inductive?

George H.

I refuse to watch Squeaky's videos.

I understand, he was pulling apart an ovenized x-tal oscilator
someone sent him. Then this bifilar inductor appeared.
Maybe 1.5" of ferrite rod with ~10 turns of paired wire,
maybe 20AWG, not twisted. The schematic drew it as
an inductor on the AC input line to some lamp power supply.

A bifilar inductor is really a 1:1 transformer with both windings made
at once from a twisted pair. So it has very low leakage inductance and
lots of inter-winding capacitance.

OK a 1:1 transformer wired top to bottom..(I don't know the right terms.)
I guess my mind thinks that to first order there is no B-field.
But of course there has to be some...My 2nd model has
a bunch of alternating rings of current.
OK and then a bunch of capacitance....It's a
50/60 Hz 2 pole band pass filter?
That's not right, it doesn't block DC.

https://www.digikey.com/product-detail/en/eaton/DRQ127-3R3-R/513-1308-2-ND/667268

Huh, I never knew of such things. You can make each series or parallel
connection in two ways... (I'll have to read the spec sheet...
I wish I had some good book/app note for transformer/inductor things,
I've used and made them, but unless I'm designing for some
magnetic field, I don't know what I'm doing.

I've read about coax/ toroid transformers in ARRL and such
but never with any deep understanding.

George H.

These are sometimes sold as transformers, sometimes as dual-winding
inductors. They are inductors in the sense that the winding inductance
is specified, with a tolerance.

I love those DRQ-series gadgets. They are good for all sorts of
things.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[whit3rd]

On Thursday, January 4, 2018 at 11:37:24 AM UTC-8, George Herold wrote:

Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)
My question is; how the heck does that do anything inductive?

It's a shorted transmission line. So, there's some delay, during which it
has a characteristic impedance (ohmic) after which it's
a short circuit.

As you suggest, it only has inductive character on the scale size of
the wire separation.

So, the triac (which has a dI/dt limit) will see some nontrivial impedance for
a few nanoseconds (the ferrite makes this a SLOW shorted transmission line).
The turnon transient, then, even if there's a capacitive load, is under control.
Because it's only active for a short time, the losses are insignificant.

 

[Chris]

On Thu, 04 Jan 2018 16:42:23 -0800, John Larkin wrote:

> I refuse to watch Squeaky's videos.

Such a shame he has that *ghastly* Australian accent, the squeakiness of
which only exacerbates grating quality of. It's simply appalling and the
only thing that could make it even worse is if he were a she instead.
For Aussie Sheilas, the best investment in finding a husband would be
elocution lessons.

 

[amdx]

On 1/4/2018 6:42 PM, John Larkin wrote:

On Thu, 4 Jan 2018 11:37:19 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)
My question is; how the heck does that do anything inductive?

George H.

I refuse to watch Squeaky's videos.

A bifilar inductor is really a 1:1 transformer with both windings made
at once from a twisted pair. So it has very low leakage inductance and
lots of inter-winding capacitance.

https://www.digikey.com/product-detail/en/eaton/DRQ127-3R3-R/513-1308-2-ND/667268

These are sometimes sold as transformers, sometimes as dual-winding
inductors. They are inductors in the sense that the winding inductance
is specified, with a tolerance.

I love those DRQ-series gadgets. They are good for all sorts of
things.


Without watching the video, you missed the mark.

Mikek

 

[amdx]

On 1/4/2018 7:43 PM, George Herold wrote:

On Thursday, January 4, 2018 at 7:42:34 PM UTC-5, John Larkin wrote:
On Thu, 4 Jan 2018 11:37:19 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)
My question is; how the heck does that do anything inductive?

George H.

I refuse to watch Squeaky's videos.
I understand, he was pulling apart an ovenized x-tal oscilator
someone sent him.

Why confuse the issue by throwing in a X-tal osc?

The inductor is out of a light dimmer.

Then this bifilar inductor appeared.
Maybe 1.5" of ferrite rod with ~10 turns of paired wire,
maybe 20AWG, not twisted. The schematic drew it as
an inductor on the AC input line to some lamp power supply.

A bifilar inductor is really a 1:1 transformer with both windings made
at once from a twisted pair. So it has very low leakage inductance and
lots of inter-winding capacitance.
OK a 1:1 transformer wired top to bottom..(I don't know the right terms.)
I guess my mind thinks that to first order there is no B-field.
But of course there has to be some...My 2nd model has
a bunch of alternating rings of current.
OK and then a bunch of capacitance....It's a
50/60 Hz 2 pole band pass filter?
That's not right, it doesn't block DC.

https://www.digikey.com/product-detail/en/eaton/DRQ127-3R3-R/513-1308-2-ND/667268
Huh, I never knew of such things. You can make each series or parallel
connection in two ways... (I'll have to read the spec sheet...
I wish I had some good book/app note for transformer/inductor things,
I've used and made them, but unless I'm designing for some
magnetic field, I don't know what I'm doing.

I've read about coax/ toroid transformers in ARRL and such
but never with any deep understanding.

George H.

These are sometimes sold as transformers, sometimes as dual-winding
inductors. They are inductors in the sense that the winding inductance
is specified, with a tolerance.

I love those DRQ-series gadgets. They are good for all sorts of
things.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[amdx]

On 1/5/2018 1:44 PM, Chris wrote:

On Thu, 04 Jan 2018 16:42:23 -0800, John Larkin wrote:

I refuse to watch Squeaky's videos.

Such a shame he has that *ghastly* Australian accent, the squeakiness of
which only exacerbates grating quality of. It's simply appalling and the
only thing that could make it even worse is if he were a she instead.
For Aussie Sheilas, the best investment in finding a husband would be
elocution lessons.

There is really no reason to hate an Australian accent.
I guess you just want something to hate to make yourself feel superior.
I suspect the feeling didn't last long.

Mikek

 

[Winfield Hill]

John Larkin wrote...

George Herold wrote:

Hi all, silly question. Dave's EEVblog was on... there
was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)
My question is; how the heck does that do anything inductive?

I refuse to watch Squeaky's videos.

A bifilar inductor is really a 1:1 transformer with
both windings made at once from a twisted pair. So it
has very low leakage inductance and lots of inter-winding
capacitance.

https://www.digikey.com/product-detail/en/eaton/DRQ127-3R3-R/513-1308-2-ND/667268

These are sometimes sold as transformers, sometimes as
dual-winding inductors. They are inductors in the sense
that the winding inductance is specified, with a tolerance.

I love those DRQ-series gadgets. They are good for all
sorts of things.

One point, they are universally called coupled inductors.
Think of one winding as an inductor, e.g., used in an
inverting dc-dc converter. It'll have -Vo, plus a diode
drop across its coil as it makes a neg output. The
other winding has exactly the same voltage, use it with
a diode to make an identical positive voltage, +Vo.

I like Bourns SRF0703 series, 0.3 x 0.3 inches (half the
size of an DRQ127), only $0.13, inductances from 0.33uH
to 1000uH. One dc-dc converter IC, get bipolar +/-15V,
etc, nice! My MPX-16H high-voltage multiplexer DAQ board
uses TPS64201 with a NTS4173P FET to make a 1W converter.


--
Thanks,
- Win

 

[George Herold]

On Thursday, January 4, 2018 at 9:17:22 PM UTC-5, whit3rd wrote:

On Thursday, January 4, 2018 at 11:37:24 AM UTC-8, George Herold wrote:
Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)
My question is; how the heck does that do anything inductive?

It's a shorted transmission line. So, there's some delay, during which it
has a characteristic impedance (ohmic) after which it's
a short circuit.

As you suggest, it only has inductive character on the scale size of
the wire separation.

So, the triac (which has a dI/dt limit) will see some nontrivial impedance for
a few nanoseconds (the ferrite makes this a SLOW shorted transmission line).
The turnon transient, then, even if there's a capacitive load, is under control.
Because it's only active for a short time, the losses are insignificant.

OK that makes sense, so I think of it as an inrush current limiter?

George H.

 

[Phil Allison]

Chris wrote:

--------------

John Larkin wrote:

I refuse to watch Squeaky's videos.


Such a shame he has that *ghastly* Australian accent, the squeakiness of
which only exacerbates grating quality of.

** Hold on a mo, Australians typically don't have ghastly accents or squeaky voices. David L Jones happens to be a short person, so has a higher pitch to his voice than most. Here is a vid where he has a guest presenter, Doug Ford whom I know well.

https://www.youtube.com/watch?v=ihAG6cMpUlY

Doug is not very tall either, but he is taller than Dave and I am taller than both at 5ft 9 inches.

Doug gives a talk about microphones, devices he dealt with a fair bit once when he worked as electronics designer for Rode Microphones here in Sydney.



..... Phil

 

[Martin Riddle]

On Thu, 4 Jan 2018 17:43:21 -0800 (PST), George Herold
<gherold@teachspin.com> wrote:

On Thursday, January 4, 2018 at 7:42:34 PM UTC-5, John Larkin wrote:
On Thu, 4 Jan 2018 11:37:19 -0800 (PST), George Herold
gherold@teachspin.com> wrote:

Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)
My question is; how the heck does that do anything inductive?

George H.

I refuse to watch Squeaky's videos.
I understand, he was pulling apart an ovenized x-tal oscilator
someone sent him. Then this bifilar inductor appeared.
Maybe 1.5" of ferrite rod with ~10 turns of paired wire,
maybe 20AWG, not twisted. The schematic drew it as
an inductor on the AC input line to some lamp power supply.

A bifilar inductor is really a 1:1 transformer with both windings made
at once from a twisted pair. So it has very low leakage inductance and
lots of inter-winding capacitance.
OK a 1:1 transformer wired top to bottom..(I don't know the right terms.)
I guess my mind thinks that to first order there is no B-field.
But of course there has to be some...My 2nd model has
a bunch of alternating rings of current.
OK and then a bunch of capacitance....It's a
50/60 Hz 2 pole band pass filter?
That's not right, it doesn't block DC.

https://www.digikey.com/product-detail/en/eaton/DRQ127-3R3-R/513-1308-2-ND/667268
Huh, I never knew of such things. You can make each series or parallel
connection in two ways... (I'll have to read the spec sheet...
I wish I had some good book/app note for transformer/inductor things,
I've used and made them, but unless I'm designing for some
magnetic field, I don't know what I'm doing.

The Amidoncorp.com website has a few books on magnetics, for rf.

Cheers

 

[John Larkin]

On 5 Jan 2018 15:57:09 -0800, Winfield Hill <hill@rowland.harvard.edu>
wrote:

John Larkin wrote...
George Herold wrote:

Hi all, silly question. Dave's EEVblog was on... there
was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)
My question is; how the heck does that do anything inductive?

I refuse to watch Squeaky's videos.

A bifilar inductor is really a 1:1 transformer with
both windings made at once from a twisted pair. So it
has very low leakage inductance and lots of inter-winding
capacitance.

https://www.digikey.com/product-detail/en/eaton/DRQ127-3R3-R/513-1308-2-ND/667268

These are sometimes sold as transformers, sometimes as
dual-winding inductors. They are inductors in the sense
that the winding inductance is specified, with a tolerance.

I love those DRQ-series gadgets. They are good for all
sorts of things.

One point, they are universally called coupled inductors.
Think of one winding as an inductor, e.g., used in an
inverting dc-dc converter. It'll have -Vo, plus a diode
drop across its coil as it makes a neg output. The
other winding has exactly the same voltage, use it with
a diode to make an identical positive voltage, +Vo.

I like Bourns SRF0703 series, 0.3 x 0.3 inches (half the
size of an DRQ127), only $0.13, inductances from 0.33uH
to 1000uH. One dc-dc converter IC, get bipolar +/-15V,
etc, nice! My MPX-16H high-voltage multiplexer DAQ board
uses TPS64201 with a NTS4173P FET to make a 1W converter.

I'm using the SRF0703, 100 uH, as a mosfet gate driver.

My whine is that they don't ID pin 1. The only way to orient it is by
the value screened on top. 101 looks a lot like 101 upside-down!

Luckily, it works installed upside down. But it's hard to convince QC
of that.

https://www.dropbox.com/s/gm5syaoe83hrbco/V270_Chan.jpg?raw=1

You can do fun switcher tricks with a dual inductor.

https://www.dropbox.com/s/q8v0jbz23o9ir8z/TPS_Boost.JPG?raw=1

https://www.dropbox.com/s/yu25filnplzdq8o/ALX_DRQ_1.asc?raw=1

https://www.dropbox.com/s/0tlccbgo9gbkwm7/Dual-Winding-Boost.JPG?raw=1

https://www.dropbox.com/s/znu2e37ejl7ph0s/Flybacks.JPG?raw=1


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Winfield Hill]

John Larkin wrote...

Winfield Hill wrote:
John Larkin wrote...

A bifilar inductor is really a 1:1 transformer with
both windings made at once from a twisted pair. So it
has very low leakage inductance and lots of inter-winding
capacitance.

https://www.digikey.com/product-detail/en/eaton/DRQ127-3R3-R/513-1308-2-ND/667268

These are sometimes sold as transformers, sometimes as
dual-winding inductors. They are inductors in the sense
that the winding inductance is specified, with a tolerance.

I love those DRQ-series gadgets. They are good for all
sorts of things.

One point, they are universally called coupled inductors.
Think of one winding as an inductor, e.g., used in an
inverting dc-dc converter. It'll have -Vo, plus a diode
drop across its coil as it makes a neg output. The
other winding has exactly the same voltage, use it with
a diode to make an identical positive voltage, +Vo.

I like Bourns SRF0703 series, 0.3 x 0.3 inches (half the
size of an DRQ127), only $0.13, inductances from 0.33uH
to 1000uH. One dc-dc converter IC, get bipolar +/-15V,
etc, nice! My MPX-16H high-voltage multiplexer DAQ board
uses TPS64201 with a NTS4173P FET to make a 1W converter.

I'm using the SRF0703, 100 uH, as a mosfet gate driver.

https://www.dropbox.com/s/gm5syaoe83hrbco/V270_Chan.jpg?raw=1

Hmm, an interesting circuit. Momentarily shorting out
your source signal? Part of your SSR monitoring scheme?
That USB dpdt switch with enable is a cool part.

I'm surprised at your choice of 100V DPak MOSFET. You
have about 4V gate drive, but that 270mR part wants 10V,
is unhappy below 6V, at 4V it's Ron must be 10x higher!

Looking in my huge MOSFET table, I see a few 100V DPak
parts rated at Vgs = 4.5 or 5V, e.g., FQD13N10L 200mR,
IRLR3410, 125mR, DMN10H100SK3 100mR ...

> You can do fun switcher tricks with a dual inductor.

Coupled inductor, John. Coupled is the word to use.


--
Thanks,
- Win

 

[John Larkin]

On 6 Jan 2018 04:36:04 -0800, Winfield Hill <hill@rowland.harvard.edu>
wrote:

John Larkin wrote...

Winfield Hill wrote:
John Larkin wrote...

A bifilar inductor is really a 1:1 transformer with
both windings made at once from a twisted pair. So it
has very low leakage inductance and lots of inter-winding
capacitance.

https://www.digikey.com/product-detail/en/eaton/DRQ127-3R3-R/513-1308-2-ND/667268

These are sometimes sold as transformers, sometimes as
dual-winding inductors. They are inductors in the sense
that the winding inductance is specified, with a tolerance.

I love those DRQ-series gadgets. They are good for all
sorts of things.

One point, they are universally called coupled inductors.
Think of one winding as an inductor, e.g., used in an
inverting dc-dc converter. It'll have -Vo, plus a diode
drop across its coil as it makes a neg output. The
other winding has exactly the same voltage, use it with
a diode to make an identical positive voltage, +Vo.

I like Bourns SRF0703 series, 0.3 x 0.3 inches (half the
size of an DRQ127), only $0.13, inductances from 0.33uH
to 1000uH. One dc-dc converter IC, get bipolar +/-15V,
etc, nice! My MPX-16H high-voltage multiplexer DAQ board
uses TPS64201 with a NTS4173P FET to make a 1W converter.

I'm using the SRF0703, 100 uH, as a mosfet gate driver.

https://www.dropbox.com/s/gm5syaoe83hrbco/V270_Chan.jpg?raw=1

Hmm, an interesting circuit. Momentarily shorting out
your source signal? Part of your SSR monitoring scheme?
That USB dpdt switch with enable is a cool part.

The current through the 1M sampling resistors is either switched to
the shared test bus, or diverted to ground. If it wasn't grounded,
some current would shoot through the switches of unselected channels.

(An undocumented problem in most cmos analog mux's is this effect,
fets turning on when inputs go wrong-side of the rails.)

USB and digital bus switches are superb analog multiplexers, at a
fraction of the price of official multiplexers.

I'm surprised at your choice of 100V DPak MOSFET. You
have about 4V gate drive, but that 270mR part wants 10V,
is unhappy below 6V, at 4V it's Ron must be 10x higher!

The gate drive will be 10 or 12 volts. It's an open-loop flyback
converter, driven by an open-drain output from a TPIC6595. The drive
duty cycle sets the gate drive voltage. That's been breadboarded.

The 0.33r wirewound resistor absorbs the energy if the user puts a
hard voltage across the SSR, and FPGA code monitors the situation and
shuts down the channel before anything (including connector pins and
PCB traces) blows up. First-article testing will be fun.

https://www.dropbox.com/s/3ek90tq9bz1p99s/V270A_PCB.jpg?raw=1

PCB design review on Monday.

Looking in my huge MOSFET table, I see a few 100V DPak
parts rated at Vgs = 4.5 or 5V, e.g., FQD13N10L 200mR,
IRLR3410, 125mR, DMN10H100SK3 100mR ...

You can do fun switcher tricks with a dual inductor.

Coupled inductor, John. Coupled is the word to use.

I ignore the Word Police.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Winfield Hill]

John Larkin wrote...

Winfield Hill wrote:
John Larkin wrote...

I'm using the SRF0703, 100 uH, as a mosfet gate driver.

https://www.dropbox.com/s/gm5syaoe83hrbco/V270_Chan.jpg?raw=1

Hmm, an interesting circuit. Momentarily shorting out
your source signal? Part of your SSR monitoring scheme?
That USB dpdt switch with enable is a cool part.

The current through the 1M sampling resistors is either
switched to the shared test bus, or diverted to ground.
If it wasn't grounded, some current would shoot through
the switches of unselected channels.

(An undocumented problem in most cmos analog mux's is this
effect, fets turning on when inputs go wrong-side of the rails.)

Interesting, even with 1M series resistance?

USB and digital bus switches are superb analog multiplexers,
at a fraction of the price of official multiplexers.

I'm surprised at your choice of 100V DPak MOSFET. You
have about 4V gate drive, but that 270mR part wants 10V,
is unhappy below 6V, at 4V it's Ron must be 10x higher!

The gate drive will be 10 or 12 volts. ...

The 0.33r wirewound resistor absorbs the energy ...

What size, p/n for the resistor? Your old IRFR120
type with 270mR max will be sharing a significant
part of the load. The DMN10H100SK3 I mentioned
has 80mR max Ron, and is cheaper, about 30 cents.


--
Thanks,
- Win

 

[John Larkin]

On 6 Jan 2018 10:05:09 -0800, Winfield Hill <hill@rowland.harvard.edu>
wrote:

John Larkin wrote...

Winfield Hill wrote:
John Larkin wrote...

I'm using the SRF0703, 100 uH, as a mosfet gate driver.

https://www.dropbox.com/s/gm5syaoe83hrbco/V270_Chan.jpg?raw=1

Hmm, an interesting circuit. Momentarily shorting out
your source signal? Part of your SSR monitoring scheme?
That USB dpdt switch with enable is a cool part.

The current through the 1M sampling resistors is either
switched to the shared test bus, or diverted to ground.
If it wasn't grounded, some current would shoot through
the switches of unselected channels.

(An undocumented problem in most cmos analog mux's is this
effect, fets turning on when inputs go wrong-side of the rails.)

Interesting, even with 1M series resistance?

Yes. Before the ESD diodes turn on, the series fets can turn on when
their sources are driven past the rails. My 70 uA of input current
would shoot through into the other signal pins. This will happen at
any current level. Some analog mux's specifically avoid this effect,
but most don't.

USB and digital bus switches are superb analog multiplexers,
at a fraction of the price of official multiplexers.

I'm surprised at your choice of 100V DPak MOSFET. You
have about 4V gate drive, but that 270mR part wants 10V,
is unhappy below 6V, at 4V it's Ron must be 10x higher!

The gate drive will be 10 or 12 volts. ...

The 0.33r wirewound resistor absorbs the energy ...

What size, p/n for the resistor? Your old IRFR120
type with 270mR max will be sharing a significant
part of the load. The DMN10H100SK3 I mentioned
has 80mR max Ron, and is cheaper, about 30 cents.

I don't think that's the actual fet on the final BOM. That schematic
is one that I have at home, not the final one. I think we're using
some 8 mohm parts in real life. We did spend a lot of time thinking
about protecting the SSRs. I tested several of the so-called
self-protecting fets, and they were various sorts of terrible.

The bottom line is that almost all the fault energy goes into the
resistor, not the fets.


I posted to s.e.d. about my resistor exploding experiments.

https://www.dropbox.com/s/5it6rgc1wxcp8ah/Ex-Resistors.JPG?raw=1

https://www.dropbox.com/s/oz62u59ourty079/Z420_C1.JPG?raw=1


My best choice was a Vishay AC05 axial wirewound, reliable when pulsed
at 15 joules.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[whit3rd]

On Friday, January 5, 2018 at 5:28:28 PM UTC-8, George Herold wrote:

On Thursday, January 4, 2018 at 9:17:22 PM UTC-5, whit3rd wrote:
On Thursday, January 4, 2018 at 11:37:24 AM UTC-8, George Herold wrote:
Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)
My question is; how the heck does that do anything inductive?

It's a shorted transmission line.

OK that makes sense, so I think of it as an inrush current limiter?

Yes, that's the function that it seems to fill. Unlike a bifilar winding on a
core, the transmission-line must be a single layer wound around that
stick of ferrite (a second layer, NOT adjacent to the ferrite, would
not be a continuation of the delay line). That's consistent with the odd
one-layer winding on a stick (and 'inductor' function is less consistent).

It's a neat measurement problem to find a way to test the gizmo
at sufficiently high current to see its 'normal' operating impedance
and delay. You want a step of a few dozen volts and an amp or
so of drive.

 

[Jasen Betts]

On 2018-01-04, George Herold <gherold@teachspin.com> wrote:

Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)

he called it "bifilar" seems more like "hairpin" wound to me.

> My question is; how the heck does that do anything inductive?

You've got near-field interaction of the individual copper wires with
the nearby bits of ferrite. and that's about it.




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This email has not been checked by half-arsed antivirus software

 

[John Larkin]

On Fri, 5 Jan 2018 17:28:23 -0800 (PST), George Herold
<gherold@teachspin.com> wrote:

On Thursday, January 4, 2018 at 9:17:22 PM UTC-5, whit3rd wrote:
On Thursday, January 4, 2018 at 11:37:24 AM UTC-8, George Herold wrote:
Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in)
https://www.eevblog.com/
(hmm latest video I guess, Mailbag #1049)
My question is; how the heck does that do anything inductive?

It's a shorted transmission line. So, there's some delay, during which it
has a characteristic impedance (ohmic) after which it's
a short circuit.

As you suggest, it only has inductive character on the scale size of
the wire separation.

So, the triac (which has a dI/dt limit) will see some nontrivial impedance for
a few nanoseconds (the ferrite makes this a SLOW shorted transmission line).
The turnon transient, then, even if there's a capacitive load, is under control.
Because it's only active for a short time, the losses are insignificant.

OK that makes sense, so I think of it as an inrush current limiter?

George H.

https://www.dropbox.com/s/c40vtp0zmfohmx8/candy2.jpg?raw=1



--

John Larkin Highland Technology, Inc

lunatic fringe electronics