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5 to 10kV rated gate transformers

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  5 to 10kV rated gate transformers Winfield Hill <hill@rowland.harvard.edu> - 2017-05-17 14:33 -0700
    Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-17 15:09 -0700
      Re: 5 to 10kV rated gate transformers Winfield Hill <hill@rowland.harvard.edu> - 2017-05-31 07:39 -0700
    Re: 5 to 10kV rated gate transformers "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-05-18 01:21 -0500
      Re: 5 to 10kV rated gate transformers Winfield Hill <hill@rowland.harvard.edu> - 2017-05-31 07:30 -0700
    Re: 5 to 10kV rated gate transformers oldschool@tubes.com - 2017-05-18 08:34 -0400
      Re: 5 to 10kV rated gate transformers Winfield Hill <hill@rowland.harvard.edu> - 2017-05-18 10:07 -0700
        Re: 5 to 10kV rated gate transformers Klaus Kragelund <klauskvik@hotmail.com> - 2017-05-18 10:53 -0700
          Re: 5 to 10kV rated gate transformers speff <spehro@gmail.com> - 2017-05-18 12:59 -0700
          Re: 5 to 10kV rated gate transformers habib <h.bouazizviallet@free.fr> - 2017-05-31 22:03 +0200
            Re: 5 to 10kV rated gate transformers Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-05-31 13:22 -0700
              Re: 5 to 10kV rated gate transformers habib <h.bouazizviallet@free.fr> - 2017-05-31 23:04 +0200
                Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-31 15:57 -0700
                  Re: 5 to 10kV rated gate transformers Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-06-01 07:47 +0000
                    Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-01 07:13 -0700
                      Re: 5 to 10kV rated gate transformers Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-06-01 14:28 +0000
                        Re: 5 to 10kV rated gate transformers Klaus Kragelund <klauskvik@hotmail.com> - 2017-06-01 07:42 -0700
                          Re: 5 to 10kV rated gate transformers Klaus Kragelund <klauskvik@hotmail.com> - 2017-06-01 07:43 -0700
                            Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-01 08:47 -0700
                              Re: 5 to 10kV rated gate transformers klaus.kragelund@gmail.com - 2017-06-02 01:25 -0700
                                Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-02 07:59 -0700
                                  Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-02 09:21 -0700
                                    Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-02 09:32 -0700
                                      Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-02 10:08 -0700
                                        Re: 5 to 10kV rated gate transformers Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-06-02 10:21 -0700
                                          Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-02 10:46 -0700
                                            Re: 5 to 10kV rated gate transformers Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-06-02 17:54 +0000
                                        Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-02 11:02 -0700
                                          Re: 5 to 10kV rated gate transformers Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-06-02 11:05 -0700
                                          Re: 5 to 10kV rated gate transformers Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-06-02 18:16 +0000
                                          Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-02 11:32 -0700
                                            Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-02 12:15 -0700
                                              Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-02 12:43 -0700
                                  Re: 5 to 10kV rated gate transformers klaus.kragelund@gmail.com - 2017-06-02 10:04 -0700
                                    Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-02 10:54 -0700
                                      Re: 5 to 10kV rated gate transformers "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-06-02 17:35 -0500
                                        Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-02 15:56 -0700
                        Re: 5 to 10kV rated gate transformers upsidedown@downunder.com - 2017-06-01 17:44 +0300
                          Re: 5 to 10kV rated gate transformers Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-06-01 14:57 +0000
                          Re: 5 to 10kV rated gate transformers Winfield Hill <hill@rowland.harvard.edu> - 2017-06-01 08:05 -0700
                        Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-01 08:45 -0700
                          Re: 5 to 10kV rated gate transformers Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-06-01 16:07 +0000
                            Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-02 11:08 -0700
                              Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-02 11:37 -0700
                    Re: 5 to 10kV rated gate transformers Klaus Kragelund <klauskvik@hotmail.com> - 2017-06-01 07:33 -0700
                      Re: 5 to 10kV rated gate transformers Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-06-01 14:56 +0000
          Re: 5 to 10kV rated gate transformers upsidedown@downunder.com - 2017-06-01 12:08 +0300
            Re: 5 to 10kV rated gate transformers habib.bouaziz@gmail.com - 2017-06-01 04:12 -0700
            Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-01 07:15 -0700
        Re: 5 to 10kV rated gate transformers Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-18 20:08 +0000
        Re: 5 to 10kV rated gate transformers upsidedown@downunder.com - 2017-05-19 00:03 +0300
        Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-18 14:12 -0700
    Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-05-31 10:48 -0700
    Re: 5 to 10kV rated gate transformers habib <h.bouazizviallet@free.fr> - 2017-05-31 21:50 +0200
      Re: 5 to 10kV rated gate transformers Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-05-31 12:57 -0700
        Re: 5 to 10kV rated gate transformers habib <h.bouazizviallet@free.fr> - 2017-05-31 22:10 +0200
          Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-01 13:09 -0700
            Re: 5 to 10kV rated gate transformers habib <h.bouazizviallet@free.fr> - 2017-06-01 23:17 +0200
              Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-01 14:35 -0700
                Re: 5 to 10kV rated gate transformers habib.bouaziz@gmail.com - 2017-06-02 07:01 -0700
                  Re: 5 to 10kV rated gate transformers Winfield Hill <hill@rowland.harvard.edu> - 2017-06-02 08:44 -0700
                    Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-02 09:19 -0700
                      Re: 5 to 10kV rated gate transformers Winfield Hill <hill@rowland.harvard.edu> - 2017-06-02 11:18 -0700
                    Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-02 09:28 -0700
                      Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-02 09:35 -0700
                        Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-02 11:16 -0700
                          Re: 5 to 10kV rated gate transformers Winfield Hill <hill@rowland.harvard.edu> - 2017-06-02 14:02 -0700
                            Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-02 14:36 -0700
                            Re: 5 to 10kV rated gate transformers John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-02 16:08 -0700
                    Re: 5 to 10kV rated gate transformers Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-06-02 16:46 +0000
                    Re: 5 to 10kV rated gate transformers habib <h.bouazizviallet@free.fr> - 2017-06-02 23:13 +0200
                      Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-02 14:39 -0700
                        Re: 5 to 10kV rated gate transformers habib <h.bouazizviallet@free.fr> - 2017-06-03 09:47 +0200
                          Re: 5 to 10kV rated gate transformers klaus.kragelund@gmail.com - 2017-06-03 04:28 -0700
                          Re: 5 to 10kV rated gate transformers Jasen Betts <jasen@xnet.co.nz> - 2017-06-07 20:03 +0000
                    Re: 5 to 10kV rated gate transformers Winfield Hill <hill@rowland.harvard.edu> - 2017-06-08 10:12 -0700
                      Re: 5 to 10kV rated gate transformers dagmargoodboat@yahoo.com - 2017-07-13 07:35 -0700
    Re: 5 to 10kV rated gate transformers Terry <respect__privacy@hotmail.com> - 2017-06-02 06:06 -0700
      Re: 5 to 10kV rated gate transformers Joerg <news@analogconsultants.com> - 2017-06-02 09:27 -0700
    Re: 5 to 10kV rated gate transformers bloggs.fredbloggs.fred@gmail.com - 2017-07-13 07:43 -0700

Page 4 of 4 — ← Prev page 1 2 3 [4]

#462681

 habib wrote...
> Joerg wrote...
>>
>> I think Win meant regular transformers although
>> he'll probably be open to PCB versions.

> not on standard transfomer products but they
> can do it on custom spec.

 I wrote earlier that I'm evaluating CM chokes.
 "I settled on a Panasonic ELF-21C023A.  It has
 Lm = 1.7mH, Ll = 40uH and Rcoil = 0.08 ohms. 
 An 100kHz H-bridge running from 24V, with 1N5819
 Schottky bridge rectifier, makes a 24.5V output,
 into 5mA load, 23.6V at 25mA, according to SPICE,
 for +20,-4V SiC drive.  The magnetizing current
 (discharge / charge the bulk cap) is 66mA p-p.
 [not bad]  My next step, play with potting and
 a month-long 2x overvoltage test at 10kV."
 https://www.digikey.com/products/en?keywords=ELF-21C023A

 I'm preparing the potting fixture now.  That
 will make this a custom transformer. :-)  The
 Panasonic transformer looks well suited, with
 thick bobbin insulating plastic, and generous
 room for further insulation through potting.
 Only need to handle 2.5kV to the ferrite core.

 Another parameter, the coil-coil capacitance
 is under 2pF.  Amazing, I had budgeted to 10pF.


-- 
 Thanks,
    - Win

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#462683

On 2017-06-02 08:44, Winfield Hill wrote:
>   habib wrote...
>> Joerg wrote...
>>>
>>> I think Win meant regular transformers although
>>> he'll probably be open to PCB versions.
>
>> not on standard transfomer products but they
>> can do it on custom spec.
>
>   I wrote earlier that I'm evaluating CM chokes.
>   "I settled on a Panasonic ELF-21C023A.  It has
>   Lm = 1.7mH, Ll = 40uH and Rcoil = 0.08 ohms.
>   An 100kHz H-bridge running from 24V, with 1N5819
>   Schottky bridge rectifier, makes a 24.5V output,
>   into 5mA load, 23.6V at 25mA, according to SPICE,
>   for +20,-4V SiC drive.  The magnetizing current
>   (discharge / charge the bulk cap) is 66mA p-p.
>   [not bad]  My next step, play with potting and
>   a month-long 2x overvoltage test at 10kV."


That does not guarantee that miniscule destruction won't be creeping in. 
Meaning the transformer is going to be compromised after that month and 
there is no telling by how much. This is why hipot tests at the end of 
production are usually limited to a minute or less.


>   https://www.digikey.com/products/en?keywords=ELF-21C023A
>

Says "AC 250 Vrms max" which would be the rated maximum working voltage.


>   I'm preparing the potting fixture now.  That
>   will make this a custom transformer. :-)  The
>   Panasonic transformer looks well suited, with
>   thick bobbin insulating plastic, and generous
>   room for further insulation through potting.
>   Only need to handle 2.5kV to the ferrite core.
>

Even if you assume the low end of your spec (5kV) you can't assume that 
the core will always sit at exactly half between the coils. At least not 
for low frequency AC or DC. Creepage, contamination, capacitance 
difference and all that can make this voltage divider lopsided.


>   Another parameter, the coil-coil capacitance
>   is under 2pF.  Amazing, I had budgeted to 10pF.
>

It might all "work" but in a design review for a commercial product this 
would be flagged or at least should be.

-- 
Regards, Joerg

http://www.analogconsultants.com/

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#462725

Joerg wrote...
>
>On 2017-06-02 08:44, Winfield Hill wrote:
>>
>>   a month-long 2x overvoltage test at 10kV."
>
> That does not guarantee that miniscule destruction
> won't be creeping in. Meaning the transformer is
> going to be compromised after that month ...

 Right.  The transformer(s) will be tossed. 
 Any such tests have to be only "design" tests.

>>  Only need to handle 2.5kV to the ferrite core.
>
> Even if you assume the low end of your spec (5kV)
> you can't assume that the core will always sit
> at exactly half between the coils. 

 True.

> It might all "work" but in a design review for
> a commercial product this would be flagged or
> at least should be.

 I totally agree.  I'm just looking for something
 we can use in our lab that doesn't cost too much
 for 140 pieces, and won't be failing all the time.

 I used to have to replace 10kV-rated KiloVolt
 $150 reed relays running at 6kV, every 6 months.
 So I have a healthy respect for those horrible
 gradual potting failures.


-- 
 Thanks,
    - Win

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#462686

On 2 Jun 2017 08:44:20 -0700, Winfield Hill <hill@rowland.harvard.edu>
wrote:

> habib wrote...
>> Joerg wrote...
>>>
>>> I think Win meant regular transformers although
>>> he'll probably be open to PCB versions.
>
>> not on standard transfomer products but they
>> can do it on custom spec.
>
> I wrote earlier that I'm evaluating CM chokes.
> "I settled on a Panasonic ELF-21C023A.  It has
> Lm = 1.7mH, Ll = 40uH and Rcoil = 0.08 ohms. 
> An 100kHz H-bridge running from 24V, with 1N5819
> Schottky bridge rectifier, makes a 24.5V output,
> into 5mA load, 23.6V at 25mA, according to SPICE,
> for +20,-4V SiC drive.  The magnetizing current
> (discharge / charge the bulk cap) is 66mA p-p.
> [not bad]  My next step, play with potting and
> a month-long 2x overvoltage test at 10kV."
> https://www.digikey.com/products/en?keywords=ELF-21C023A

With pads, that will have about 15mm of surface creepage distance; on
your PCB and on the part itself, unless you bring wires out of your
potting or something. Seems labor intensive.

>
> I'm preparing the potting fixture now.  That
> will make this a custom transformer. :-)  The
> Panasonic transformer looks well suited, with
> thick bobbin insulating plastic, and generous
> room for further insulation through potting.
> Only need to handle 2.5kV to the ferrite core.
>
> Another parameter, the coil-coil capacitance
> is under 2pF.  Amazing, I had budgeted to 10pF.

Potting is a sticky, ugly mess. You need to measure, mix, degass,
pour, wait, clean up.

I like the idea of drum cores or pot cores on opposite sides of a PCB,
but nobody else seems interested. Imagine just a couple of cheap
pick-and-place inductors doing the job. 


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#462689

On 2017-06-02 09:28, John Larkin wrote:
> On 2 Jun 2017 08:44:20 -0700, Winfield Hill <hill@rowland.harvard.edu>
> wrote:

[...]


>> I'm preparing the potting fixture now.  That
>> will make this a custom transformer. :-)  The
>> Panasonic transformer looks well suited, with
>> thick bobbin insulating plastic, and generous
>> room for further insulation through potting.
>> Only need to handle 2.5kV to the ferrite core.
>>
>> Another parameter, the coil-coil capacitance
>> is under 2pF.  Amazing, I had budgeted to 10pF.
>
> Potting is a sticky, ugly mess. You need to measure, mix, degass,
> pour, wait, clean up.
>
> I like the idea of drum cores or pot cores on opposite sides of a PCB,
> but nobody else seems interested. Imagine just a couple of cheap
> pick-and-place inductors doing the job.
>

AFAIK you can't buy an open half pot core as a standard part. I'd be all 
ears if you could.

Upright unshielded rod inductors, yes, but their spew around EMI to no 
end. They are like a dirt bike with the muffler sawed off.

-- 
Regards, Joerg

http://www.analogconsultants.com/

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#462724

On Fri, 02 Jun 2017 09:35:55 -0700, Joerg <news@analogconsultants.com>
wrote:

>On 2017-06-02 09:28, John Larkin wrote:
>> On 2 Jun 2017 08:44:20 -0700, Winfield Hill <hill@rowland.harvard.edu>
>> wrote:
>
>[...]
>
>
>>> I'm preparing the potting fixture now.  That
>>> will make this a custom transformer. :-)  The
>>> Panasonic transformer looks well suited, with
>>> thick bobbin insulating plastic, and generous
>>> room for further insulation through potting.
>>> Only need to handle 2.5kV to the ferrite core.
>>>
>>> Another parameter, the coil-coil capacitance
>>> is under 2pF.  Amazing, I had budgeted to 10pF.
>>
>> Potting is a sticky, ugly mess. You need to measure, mix, degass,
>> pour, wait, clean up.
>>
>> I like the idea of drum cores or pot cores on opposite sides of a PCB,
>> but nobody else seems interested. Imagine just a couple of cheap
>> pick-and-place inductors doing the job.
>>
>
>AFAIK you can't buy an open half pot core as a standard part. I'd be all 
>ears if you could.

They come in pairs, and the circuit would need two. Using pot core
halves on opposite sides of the board does require terminating
windings manually, and securing the cores to the board somehow. Some
standard surface-mount inductors would be a lot better for production.


>
>Upright unshielded rod inductors, yes, but their spew around EMI to no 
>end. They are like a dirt bike with the muffler sawed off.

I designed one electric meter for a giant northeast utility. It had to
be read out without line power (this was to go into a country where
the power was erratic) so the readout wand used magnetic coupling for
data and to briefly power up the meter. I used flat rod-type inductors
on both ends, resonated, which gave pretty good coupling when they
were parallel, maybe an inch apart.


-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

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

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#462746

John Larkin wrote...
> Joerg wrote:
>> John Larkin wrote:
>>>
>>> I like the idea of drum cores or pot cores on opposite
>>> sides of a PCB, but nobody else seems interested.
>>> Imagine just a couple of cheap pick-and-place
>>> inductors doing the job.
>>
>> AFAIK you can't buy an open half pot core as a
>> standard part.  I'd be all ears if you could.
>
> They come in pairs, and the circuit would need two.
> Using pot core halves on opposite sides of the board
> does require terminating windings manually, and
> securing the cores to the board somehow. 

 Yes, but interesting idea, I like it.  Epoxy.

> Some standard surface-mount inductors would be
> a lot better for production.
>
>> Upright unshielded rod inductors, yes, but their
>> spew around EMI to no end.  They are like a dirt
>> bike with the muffler sawed off.

 Eww!

> I designed one electric meter for a giant northeast
> utility. It had to be read out without line power
> (this was to go into a country where the power was
> erratic) so the readout wand used magnetic coupling
> for data and to briefly power up the meter. I used
> flat rod-type inductors on both ends, resonated,
> which gave pretty good coupling when they were
> parallel, maybe an inch apart.

 What kind of power-coupling did you get?

 "flat rod-type" what does that mean?  I couldn't
 find available ferrite shapes for the HV design
 concepts I played with.  "bar and frame" sounded
 good, but I couldn't find inventory given that
 CCFL went out of flavor.  Not even on Alibaba.


-- 
 Thanks,
    - Win

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#462752

On 2017-06-02 14:02, Winfield Hill wrote:
> John Larkin wrote...

[...]

>> I designed one electric meter for a giant northeast
>> utility. It had to be read out without line power
>> (this was to go into a country where the power was
>> erratic) so the readout wand used magnetic coupling
>> for data and to briefly power up the meter. I used
>> flat rod-type inductors on both ends, resonated,
>> which gave pretty good coupling when they were
>> parallel, maybe an inch apart.
>
>   What kind of power-coupling did you get?
>

It can be quite high. The key is the word "resonated" that John 
mentioned. You have to scale down to your coil size:

http://pe.org.pl/articles/2013/5/37.pdf

Thing is, resonant won't likely work if you want to pulse a gate.


>   "flat rod-type" what does that mean?  I couldn't
>   find available ferrite shapes for the HV design
>   concepts I played with.  "bar and frame" sounded
>   good, but I couldn't find inventory given that
>   CCFL went out of flavor.  Not even on Alibaba.
>

Maybe you can find some stuff for experiments here:

http://www.amazing1.com/transformers-high-voltage-high-frequency.html

-- 
Regards, Joerg

http://www.analogconsultants.com/

[toc] | [prev] | [next] | [standalone]

#462769

On 2 Jun 2017 14:02:05 -0700, Winfield Hill <hill@rowland.harvard.edu>
wrote:

>John Larkin wrote...
>> Joerg wrote:
>>> John Larkin wrote:
>>>>
>>>> I like the idea of drum cores or pot cores on opposite
>>>> sides of a PCB, but nobody else seems interested.
>>>> Imagine just a couple of cheap pick-and-place
>>>> inductors doing the job.
>>>
>>> AFAIK you can't buy an open half pot core as a
>>> standard part.  I'd be all ears if you could.
>>
>> They come in pairs, and the circuit would need two.
>> Using pot core halves on opposite sides of the board
>> does require terminating windings manually, and
>> securing the cores to the board somehow. 
>
> Yes, but interesting idea, I like it.  Epoxy.
>
>> Some standard surface-mount inductors would be
>> a lot better for production.
>>
>>> Upright unshielded rod inductors, yes, but their
>>> spew around EMI to no end.  They are like a dirt
>>> bike with the muffler sawed off.
>
> Eww!
>
>> I designed one electric meter for a giant northeast
>> utility. It had to be read out without line power
>> (this was to go into a country where the power was
>> erratic) so the readout wand used magnetic coupling
>> for data and to briefly power up the meter. I used
>> flat rod-type inductors on both ends, resonated,
>> which gave pretty good coupling when they were
>> parallel, maybe an inch apart.
>
> What kind of power-coupling did you get?

It's been a while. It was probably some 10s of milliwatts.

>
> "flat rod-type" what does that mean?  I couldn't
> find available ferrite shapes for the HV design
> concepts I played with.  "bar and frame" sounded
> good, but I couldn't find inventory given that
> CCFL went out of flavor.  Not even on Alibaba.

I used a roughly 1" long dumb-bell sort of ferrite core, basically a
rod with bulges on both ends. That gave fairly good mag coupling
between parallel antennas.

I did this for Niagra Mohawk, who wanted to install these meters all
over India. In India, some good fraction of the power is stolen, so we
had some anti-tamper features in the meter, to detect bypassing and
such. It never got to production.

The split pot core thing should have good coupling. I like the
surface-mount drum cores on opposite sides, all surface-mount with no
wires or glue, but the magtetic path would have a lot of air gap as
compared to the pot core halves. Might work, though.


-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

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

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#462690

On a sunny day (2 Jun 2017 08:44:20 -0700) it happened Winfield Hill
<hill@rowland.harvard.edu> wrote in <ogs14k01lfu@drn.newsguy.com>:

> habib wrote...
>> Joerg wrote...
>>>
>>> I think Win meant regular transformers although
>>> he'll probably be open to PCB versions.
>
>> not on standard transfomer products but they
>> can do it on custom spec.
>
> I wrote earlier that I'm evaluating CM chokes.
> "I settled on a Panasonic ELF-21C023A.  It has
> Lm = 1.7mH, Ll = 40uH and Rcoil = 0.08 ohms. 
> An 100kHz H-bridge running from 24V, with 1N5819
> Schottky bridge rectifier, makes a 24.5V output,
> into 5mA load, 23.6V at 25mA, according to SPICE,
> for +20,-4V SiC drive.  The magnetizing current
> (discharge / charge the bulk cap) is 66mA p-p.
> [not bad]  My next step, play with potting and
> a month-long 2x overvoltage test at 10kV."
> https://www.digikey.com/products/en?keywords=ELF-21C023A

Did you test for flash-over between windings and core at 20 kV?

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#462748

Le 02/06/2017 à 17:44, Winfield Hill a écrit :
> My next step, play with potting and
>   a month-long 2x overvoltage test at 10kV."
>   https://www.digikey.com/products/en?keywords=ELF-21C023A
> 
>   I'm preparing the potting fixture now
> 
> .  That
>   will make this a custom transformer.

Ok. What sort of potting are you using, I remember the resin they used 
was a polyurethan compound (from Axson) which is quite dangerous to 
handle and degassing could occur during polymerization ... I've always 
consider those HV components suspicious.

Be careful Win ! Habib

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#462754

On 2017-06-02 14:13, habib wrote:
> Le 02/06/2017 à 17:44, Winfield Hill a écrit :
>> My next step, play with potting and
>>   a month-long 2x overvoltage test at 10kV."
>>   https://www.digikey.com/products/en?keywords=ELF-21C023A
>>
>>   I'm preparing the potting fixture now
>>
>> .  That
>>   will make this a custom transformer.
>
> Ok. What sort of potting are you using, I remember the resin they used
> was a polyurethan compound (from Axson) which is quite dangerous to
> handle and degassing could occur during polymerization ... I've always
> consider those HV components suspicious.
>

Win's lab:

http://i.dailymail.co.uk/i/pix/2015/11/26/12/2ED34DBF00000578-0-image-a-27_1448542599816.jpg

:-)

-- 
Regards, Joerg

http://www.analogconsultants.com/

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#462831

Le 02/06/2017 à 23:39, Joerg a écrit :
> On 2017-06-02 14:13, habib wrote:
>> Le 02/06/2017 à 17:44, Winfield Hill a écrit :
>>> My next step, play with potting and
>>>   a month-long 2x overvoltage test at 10kV."
>>>   https://www.digikey.com/products/en?keywords=ELF-21C023A
>>>
>>>   I'm preparing the potting fixture now
>>>
>>> .  That
>>>   will make this a custom transformer.
>>
>> Ok. What sort of potting are you using, I remember the resin they used
>> was a polyurethan compound (from Axson) which is quite dangerous to
>> handle and degassing could occur during polymerization ... I've always
>> consider those HV components suspicious.
>>
> 
> Win's lab:
> 
> http://i.dailymail.co.uk/i/pix/2015/11/26/12/2ED34DBF00000578-0-image-a-27_1448542599816.jpg 
> 
> 
> :-)
> 

The trash near the inflamed desk on which "ON" is written and the two 
guys not so impressed ... i suspect this was not the first shot ... next 
time it will be the building itself going to blow !

Winfield keep calm and gentle ;-)

Habib

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#462838

On Saturday, 3 June 2017 09:47:17 UTC+2, habib  wrote:
> Le 02/06/2017 à 23:39, Joerg a écrit :
> > On 2017-06-02 14:13, habib wrote:
> >> Le 02/06/2017 à 17:44, Winfield Hill a écrit :
> >>> My next step, play with potting and
> >>>   a month-long 2x overvoltage test at 10kV."
> >>>   https://www.digikey.com/products/en?keywords=ELF-21C023A
> >>>
> >>>   I'm preparing the potting fixture now
> >>>
> >>> .  That
> >>>   will make this a custom transformer.
> >>
> >> Ok. What sort of potting are you using, I remember the resin they used
> >> was a polyurethan compound (from Axson) which is quite dangerous to
> >> handle and degassing could occur during polymerization ... I've always
> >> consider those HV components suspicious.
> >>
> > 
> > Win's lab:
> > 
> > http://i.dailymail.co.uk/i/pix/2015/11/26/12/2ED34DBF00000578-0-image-a-27_1448542599816.jpg 
> > 
> > 
> > :-)
> > 
> 
> The trash near the inflamed desk on which "ON" is written and the two 
> guys not so impressed ... i suspect this was not the first shot ... next 
> time it will be the building itself going to blow !
> 

I once worked as a trainee for a company that developed 1MW UPS supplies. A senior engineer was often smoking with a pipe in his mouth. He came by, and looked into a 220kW converter and right there an IGBT blew, making a VERY load noise. Amazingly he didn't twitch, or loose the pipe. The coolest engineer I ever met

Cheers

Klaus

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#463472

On 2017-06-03, habib <h.bouazizviallet@free.fr> wrote:
> Le 02/06/2017 à 23:39, Joerg a écrit :
>> On 2017-06-02 14:13, habib wrote:
>>> Le 02/06/2017 à 17:44, Winfield Hill a écrit :
>>>> My next step, play with potting and
>>>>   a month-long 2x overvoltage test at 10kV."
>>>>   https://www.digikey.com/products/en?keywords=ELF-21C023A
>>>>
>>>>   I'm preparing the potting fixture now
>>>>
>>>> .  That
>>>>   will make this a custom transformer.
>>>
>>> Ok. What sort of potting are you using, I remember the resin they used
>>> was a polyurethan compound (from Axson) which is quite dangerous to
>>> handle and degassing could occur during polymerization ... I've always
>>> consider those HV components suspicious.
>>>
>> 
>> Win's lab:
>> 
>> http://i.dailymail.co.uk/i/pix/2015/11/26/12/2ED34DBF00000578-0-image-a-27_1448542599816.jpg 
>> 
>> 
>> :-)
>> 
>
> The trash near the inflamed desk on which "ON" is written and the two 
> guys not so impressed ... i suspect this was not the first shot ... next 
> time it will be the building itself going to blow !
>

That looks a bit like like my high-school chemistry class, probably zinc and sulphur reacting.
the teacher knew how much to use to get the flames up to the ceiling.


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

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#463559

Winfield Hill wrote...
>
> I wrote earlier that I'm evaluating CM chokes.
> "I settled on a Panasonic ELF-21C023A.  It has
> Lm = 1.7mH, Ll = 40uH and Rcoil = 0.08 ohms. 
> An 100kHz H-bridge running from 24V, with 1N5819
> Schottky bridge rectifier, makes a 24.5V output,
> into 5mA load, 23.6V at 25mA, according to SPICE,
> for +20,-4V SiC drive.  The magnetizing current
> (discharge / charge the bulk cap) is 66mA p-p.
> [not bad]  My next step, play with potting and
> a month-long 2x overvoltage test at 10kV."
> https://www.digikey.com/products/en?keywords=ELF-21C023A
>
> I'm preparing the potting fixture now.  That
> will make this a custom transformer. :-)  The
> Panasonic transformer looks well suited, with
> thick bobbin insulating plastic, and generous
> room for further insulation through potting.
> Only need to handle 2.5kV to the ferrite core.
>
> Another parameter, the coil-coil capacitance
> is under 2pF.  Amazing, I had budgeted to 10pF.

 After epoxy potting, the capacitance increased
 to 3 pF.  Next, prolonged HV insulation tests.
 Within the epoxy potting, there's about 2 mm**
 clearance to the core and 5 mm coil-to-coil.
 External wiring creepage distance is 17 mm.
 Typical material specs range from 12 to 20kV/mm,
 or 24kV min for 2mm.  Maybe I'll test at 15kV.
 (The maximum it'll ever encounter in my +/-5kV
 bipolar switch is 5kV dc for a few hours.)


-- 
 Thanks,
    - Win

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#468232

On Thursday, June 8, 2017 at 1:12:57 PM UTC-4, Winfield Hill wrote:
> Winfield Hill wrote...
> >
> > I wrote earlier that I'm evaluating CM chokes.
> > "I settled on a Panasonic ELF-21C023A.  It has
> > Lm = 1.7mH, Ll = 40uH and Rcoil = 0.08 ohms. 
> > An 100kHz H-bridge running from 24V, with 1N5819
> > Schottky bridge rectifier, makes a 24.5V output,
> > into 5mA load, 23.6V at 25mA, according to SPICE,
> > for +20,-4V SiC drive.  The magnetizing current
> > (discharge / charge the bulk cap) is 66mA p-p.
> > [not bad]  My next step, play with potting and
> > a month-long 2x overvoltage test at 10kV."
> > https://www.digikey.com/products/en?keywords=ELF-21C023A
> >
> > I'm preparing the potting fixture now.  That
> > will make this a custom transformer. :-)  The
> > Panasonic transformer looks well suited, with
> > thick bobbin insulating plastic, and generous
> > room for further insulation through potting.
> > Only need to handle 2.5kV to the ferrite core.
> >
> > Another parameter, the coil-coil capacitance
> > is under 2pF.  Amazing, I had budgeted to 10pF.
> 
>  After epoxy potting, the capacitance increased
>  to 3 pF.  Next, prolonged HV insulation tests.
>  Within the epoxy potting, there's about 2 mm**
>  clearance to the core and 5 mm coil-to-coil.
>  External wiring creepage distance is 17 mm.
>  Typical material specs range from 12 to 20kV/mm,
>  or 24kV min for 2mm.  Maybe I'll test at 15kV.
>  (The maximum it'll ever encounter in my +/-5kV
>  bipolar switch is 5kV dc for a few hours.)
> 
> 
> -- 
>  Thanks,
>     - Win

Win,

Did you notice Digikey has your part status marked "obsolete"?

I'm working on a pulser too.  Mine's 10MHz, lower voltage (V = 0 to +/-1kV),
transitions under 10nS, and I'm deciding between stacks of silicon FETs or
pairs of the Cree/Wolfspeed C2M SiC FETs.

A drawback of the usual FET stacks is that I have to turn 'off' quickly too.

Since I only need 1kV, I find this MuRata dc-dc converter interesting
as a potential power supply for the isolated gate drive...

https://www.digikey.com/product-detail/en/murata-power-solutions-inc/NXJ1S1215MC-R7/811-3097-1-ND/5697924

It uses a pcb transformer, it's surface-mount, 4.2kV-rated, and Ciso = 2.5pF.
14x11mm, and under $4 in singles.

Cheers,
James Arthur

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#462672

Although not marketed as a transformer, most common-mode chokes can give 10KV isolation, provided that you coat or pot them in suitable material, including the connection pins where the solder to the PCB.  Be sure to give adequate creepage/clearance on your board, or solder wires made from HV insulated wire, and mount them off the PCB.  This will NOT be safety agency approved however, so it's not for use in anything that's AC Mains connected, or in Medical equipment.

In a similar line of practice, you can take a pair of well insulated current transformers that are encased in potting and include a thick plastic shell.  If lay them end to end, and loop 10-20 turns of wire through their pick-up holes, then short the wire ends, you'll have created your own transformer.  Even better is to insert some layers of insulated sleeve/tubing (into the holes), which is safety agency approved for the voltage you need to withstand.  

If you don't need tight magnetic coupling  (i.e. Some air gap is ok), then how about two off-the-shelf rod inductors laying side by side, separated by some suitable thickness of approved insulation material in between?

A final suggestion is to contact MPS Industries, in Gardena California.  They can provide design assistance, and they actually love to do small production runs and/or prototype builds.

Regards,  Terry Moreau

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#462685

On 2017-06-02 06:06, Terry wrote:
> Although not marketed as a transformer, most common-mode chokes can
> give 10KV isolation, provided that you coat or pot them in suitable
> material, including the connection pins where the solder to the PCB.
> Be sure to give adequate creepage/clearance on your board, or solder
> wires made from HV insulated wire, and mount them off the PCB.  This
> will NOT be safety agency approved however, so it's not for use in
> anything that's AC Mains connected, or in Medical equipment.
>

For very good reason. Applying hipot level voltages continuously to a 
part that is only breakdown-rated at that level will degrade the 
isolation properties over time.


> In a similar line of practice, you can take a pair of well insulated
> current transformers that are encased in potting and include a thick
> plastic shell.  If lay them end to end, and loop 10-20 turns of wire
> through their pick-up holes, then short the wire ends, you'll have
> created your own transformer.  Even better is to insert some layers
> of insulated sleeve/tubing (into the holes), which is safety agency
> approved for the voltage you need to withstand.
>
> If you don't need tight magnetic coupling  (i.e. Some air gap is ok),
> then how about two off-the-shelf rod inductors laying side by side,
> separated by some suitable thickness of approved insulation material
> in between?
>
> A final suggestion is to contact MPS Industries, in Gardena
> California.  They can provide design assistance, and they actually
> love to do small production runs and/or prototype builds.
>

Pot cores are also very nice devices for HV apps. You can insert gap 
material that is highly isolating but all across the core halves. 
Meaning no screw going through them. Just like rotational couplers are 
made except not air.

-- 
Regards, Joerg

http://www.analogconsultants.com/

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#468236

On Wednesday, May 17, 2017 at 5:34:00 PM UTC-4, Winfield Hill wrote:
> Suggestions for sources of gate transformers, rated for 5 to 10kV continuous DC.
> Or actually, small 1:1 or 1:2 transformers to make simple dc-dc converters for
> 5kV gate-drive.
> 
> Will need 100 to 200 pieces, or more.  Parts test rated for 5kV for one second,
> or even for 1 minute, are not acceptable.  Maybe parts rated for 15kV for one
> minute would be good enough.  I can design and hand-wind transformers to meet
> this spec, but sheesh, I don't want to wind 200 or more transformers!
> 
> 
> -- 
>  Thanks,
>     - Win

Maybe find out who distributes these, they do custom:
http://www.globalsources.com/gsol/I/Pulse-transformer/p/sm/1061625154.htm#1061625154

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