Galvanic isolation without transformers ??

On Sat, 29 Nov 2014 01:41:26 -0600, John Fields
<jfields@austininstruments.com> wrote:

>
>>The C in your circuit acts like a dropper or ballast, it doesn't give =
full isolation. Touch the load and you can still get a shock. Cs on both =
L&N give a load floating at half mains V, ground the load and i doubles.
>
>I disagree in that the shock can only occur if the toucher isn't
>floating, and since the capacitors' dielectric provides the
>insulation to prevent ohmic contact between the load and either side
>of the mains, the load is, by definition, isolated.
>
>In addition, the OP's:
>
>"Indeed, it is very much possible to provide galvanic isolation with
>capacitors for AC, and in fact, capacitive reactance may be used to
>reduce high mains side current(5A) on manageable isolated load side,
>as well."
>
>seems to indicate interest in situations where the load will be
>floating, so even a single-capacitor solution should work for him.
>---
>
>>I've long thought that CR droppers would make the basis of good power =
supplies for sub-mA [touchable] loads, and could be allowed quite safely.
>
>---
>I'd only ever advocate the use of a reactively controlled supply if
>it was used in a double-insulated device.=20

On Sat, 29 Nov 2014 01:41:26 -0600, John Fields
<jfields@austininstruments.com> wrote:

>
>>The C in your circuit acts like a dropper or ballast, it doesn't give =
full isolation. Touch the load and you can still get a shock. Cs on both =
L&N give a load floating at half mains V, ground the load and i doubles.
>
>I disagree in that the shock can only occur if the toucher isn't
>floating, and since the capacitors' dielectric provides the
>insulation to prevent ohmic contact between the load and either side
>of the mains, the load is, by definition, isolated.

I disagree.  Due to the possibly substantial currents that may flow
through the cap dropper it is not isolated.  Nor do i think that is =
within
the meaning intended by the NEC and regulators.

?-)
=20
>
>In addition, the OP's:
>
>"Indeed, it is very much possible to provide galvanic isolation with
>capacitors for AC, and in fact, capacitive reactance may be used to
>reduce high mains side current(5A) on manageable isolated load side,
>as well."
>
>seems to indicate interest in situations where the load will be
>floating, so even a single-capacitor solution should work for him.
>---
>
>>I've long thought that CR droppers would make the basis of good power =
supplies for sub-mA [touchable] loads, and could be allowed quite safely.
>
>---
>I'd only ever advocate the use of a reactively controlled supply if
>it was used in a double-insulated device.=20

On 11/27/2014 3:12 PM, whit3rd wrote:
> On Wednesday, November 26, 2014 9:22:06 PM UTC-8, daku...@gmail.com wrote:
>
>> A voltage transformer is used to provide
>> galvanic isolation, in a power supply,
>> amongst other features. Is there another
>> way to achieve galvanic isolation ?
>
> Powered lamp, air gap, photovoltaic "solar panel"
> Motor, belt/hydraulic pump/nonconductive shaft, generator
> Buzzer, ceramic rod, contact-microphone-and-rectifiers
> Hydrolysis apparatus, low-pressure gas tubing, fuel cell
> Heat pump, circulating air or fluid, thermopile
> Battery factory...

I like the last one.  Use the incoming power to enable a PC to 
auto-trade in the stock market buying and selling making enough money to 
buy a battery factory which produces a product to power the isolated 
side of the interface after delivery by UPS... er, that's United Parcel 
Service, not Uninterruptable Power Supply.  I don't think there is 
anything uninterruptable about UPS the carrier.

-- 

Rick

On a sunny day (Sun, 30 Nov 2014 15:00:46 -0800 (PST)) it happened
risskovboligrenovering@gmail.com wrote in
<a8228060-cda4-44c6-944f-7573c17e2427@googlegroups.com>:

>On Sunday, November 30, 2014 10:46:18 PM UTC+1, Phil Hobbs wrote:
>> On 11/30/2014 4:41 PM, risskovboligrenovering@gmail.com wrote:
>> > On Sunday, November 30, 2014 2:26:18 AM UTC+1, Clifford Heath wrote:
>> >> On 29/11/14 08:23, Jasen Betts wrote:
>> >>> On 2014-11-28, Phil Allison <pallison49@gmail.com> wrote:
>> >>>> daku...@gmail.com wrote:
>> >>>>> Recently,
>> >>>>> we were discussing the general issue of
>> >>>>> galvanic isolation, and one of the items
>> >>>>> discussed was capacitive isolation. Indeed,
>> >>>>> it is very much possible to provide galvanic
>> >>>>> isolation with capacitors for AC, and in
>> >>>>> fact, capacitive reactance may be used
>> >>>>> to reduce high mains side current(5A)
>> >>>>> on manageable isolated load side, as well.
>> >>>>> May be this scheme could be used in some
>> >>>>> low power power supplies. Surely this would
>> >>>>> reduce the time needed to wind transformer
>> >>>>> coils.
>> >>>>
>> >>>>
>> >>>> ** You are talking complete bollocks.
>> >>>>
>> >>>> Capacitive *galvanic* isolation from the AC supply only works for signals - not power.
>> >>>
>> >>> increase the power frequency to several megahertzc and you can push
>> >>> quite a bit through capacitors
>> >>
>> >> 2nF requires 80MHz to reach 1 ohm. Are you sure you want a kilowatt of
>> >> 80MHz just to save on magnetics?
>> >
>> > If you need a low cost, low power supply, the high frequency low capacity coupling idea is good.
>> >
>> > The limiting factor is, beyond EMC, the approval agency maximum "leakage" current over the barrier (for domestic is is often
>> > 0.5mA at 230V ac, so the capacitance must be below 6nF)
>> >
>> > Cheers
>> >
>> > Klaus
>> >
>> 
>> Surely you risk RF burns doing this, besides all the cost and complexity 
>> disadvantages.  You might not die from a bad RF burn the way you might 
>> from 50/60 Hz, but you might wish you had. :(
>> 
>
>RF burn?
>
>Where might that come from?
>
>The HF loop is closed. Square wave generator/buffer -> Two plate capacitors -> bridge rectifier -> Load. No HF escapes the loop,
>only low frequency mains leakage is running across the barrier

Symmetry.
Ever worked with 1kW 80 MHz?

On Sun, 30 Nov 2014 21:05:58 -0800, josephkk
<joseph_barrett@sbcglobal.net> wrote:

>On Sat, 29 Nov 2014 01:41:26 -0600, John Fields
><jfields@austininstruments.com> wrote:
>
>>
>>>The C in your circuit acts like a dropper or ballast, it doesn't give full isolation. Touch the load and you can still get a shock. Cs on both L&N give a load floating at half mains V, ground the load and i doubles.
>>
>>I disagree in that the shock can only occur if the toucher isn't
>>floating, and since the capacitors' dielectric provides the
>>insulation to prevent ohmic contact between the load and either side
>>of the mains, the load is, by definition, isolated.
>
>I disagree.  Due to the possibly substantial currents that may flow
>through the cap dropper it is not isolated.  Nor do i think that is within
>the meaning intended by the NEC and regulators.

---
I believe that, strictly speaking, "isolated" means that there's no
ohmic path from the mains to the load, which is what the capacitors'
dielectric assures, regardless of the current allowed through the
load by the capacitors' reactances. 

Note also that even if direct contact is made - by a human, say -
with mains hot, as long as there's no path from the human back to
the other side of the mains, there'll be no shock hazard, no matter
the meaning "intended" by the NEC and regulators.

Not that it would be a good thing to leave exposed mains connections
flying in the breeze, I'm just trying to make a point.

On Monday, December 1, 2014 10:56:09 AM UTC+1, Jan Panteltje wrote:
> On a sunny day (Sun, 30 Nov 2014 15:00:46 -0800 (PST)) it happened
> risskovboligrenovering@gmail.com wrote in
> <a8228060-cda4-44c6-944f-7573c17e2427@googlegroups.com>:
> 
> >On Sunday, November 30, 2014 10:46:18 PM UTC+1, Phil Hobbs wrote:
> >> On 11/30/2014 4:41 PM, risskovboligrenovering@gmail.com wrote:
> >> > On Sunday, November 30, 2014 2:26:18 AM UTC+1, Clifford Heath wrote:
> >> >> On 29/11/14 08:23, Jasen Betts wrote:
> >> >>> On 2014-11-28, Phil Allison <pallison49@gmail.com> wrote:
> >> >>>> daku...@gmail.com wrote:
> >> >>>>> Recently,
> >> >>>>> we were discussing the general issue of
> >> >>>>> galvanic isolation, and one of the items
> >> >>>>> discussed was capacitive isolation. Indeed,
> >> >>>>> it is very much possible to provide galvanic
> >> >>>>> isolation with capacitors for AC, and in
> >> >>>>> fact, capacitive reactance may be used
> >> >>>>> to reduce high mains side current(5A)
> >> >>>>> on manageable isolated load side, as well.
> >> >>>>> May be this scheme could be used in some
> >> >>>>> low power power supplies. Surely this would
> >> >>>>> reduce the time needed to wind transformer
> >> >>>>> coils.
> >> >>>>
> >> >>>>
> >> >>>> ** You are talking complete bollocks.
> >> >>>>
> >> >>>> Capacitive *galvanic* isolation from the AC supply only works for signals - not power.
> >> >>>
> >> >>> increase the power frequency to several megahertzc and you can push
> >> >>> quite a bit through capacitors
> >> >>
> >> >> 2nF requires 80MHz to reach 1 ohm. Are you sure you want a kilowatt of
> >> >> 80MHz just to save on magnetics?
> >> >
> >> > If you need a low cost, low power supply, the high frequency low capacity coupling idea is good.
> >> >
> >> > The limiting factor is, beyond EMC, the approval agency maximum "leakage" current over the barrier (for domestic is is often
> >> > 0.5mA at 230V ac, so the capacitance must be below 6nF)
> >> >
> >> > Cheers
> >> >
> >> > Klaus
> >> >
> >> 
> >> Surely you risk RF burns doing this, besides all the cost and complexity 
> >> disadvantages.  You might not die from a bad RF burn the way you might 
> >> from 50/60 Hz, but you might wish you had. :(
> >> 
> >
> >RF burn?
> >
> >Where might that come from?
> >
> >The HF loop is closed. Square wave generator/buffer -> Two plate capacitors -> bridge rectifier -> Load. No HF escapes the loop,
> >only low frequency mains leakage is running across the barrier
> 
> Symmetry.

Care to elaborate how dis-symmetry causes RF burns?

> Ever worked with 1kW 80 MHz?

No. I have worked with 8MW at 4.5kHz. Does that have anything to do with this??

Regards

Klaus

On 12/01/2014 12:26 PM, Klaus Kragelund wrote:
> On Monday, December 1, 2014 10:56:09 AM UTC+1, Jan Panteltje wrote:
>> On a sunny day (Sun, 30 Nov 2014 15:00:46 -0800 (PST)) it happened
>> risskovboligrenovering@gmail.com wrote in
>> <a8228060-cda4-44c6-944f-7573c17e2427@googlegroups.com>:
>>
>>> On Sunday, November 30, 2014 10:46:18 PM UTC+1, Phil Hobbs wrote:
>>>> On 11/30/2014 4:41 PM, risskovboligrenovering@gmail.com wrote:
>>>>> On Sunday, November 30, 2014 2:26:18 AM UTC+1, Clifford Heath wrote:
>>>>>> On 29/11/14 08:23, Jasen Betts wrote:
>>>>>>> On 2014-11-28, Phil Allison <pallison49@gmail.com> wrote:
>>>>>>>> daku...@gmail.com wrote:
>>>>>>>>> Recently,
>>>>>>>>> we were discussing the general issue of
>>>>>>>>> galvanic isolation, and one of the items
>>>>>>>>> discussed was capacitive isolation. Indeed,
>>>>>>>>> it is very much possible to provide galvanic
>>>>>>>>> isolation with capacitors for AC, and in
>>>>>>>>> fact, capacitive reactance may be used
>>>>>>>>> to reduce high mains side current(5A)
>>>>>>>>> on manageable isolated load side, as well.
>>>>>>>>> May be this scheme could be used in some
>>>>>>>>> low power power supplies. Surely this would
>>>>>>>>> reduce the time needed to wind transformer
>>>>>>>>> coils.
>>>>>>>>
>>>>>>>>
>>>>>>>> ** You are talking complete bollocks.
>>>>>>>>
>>>>>>>> Capacitive *galvanic* isolation from the AC supply only works for signals - not power.
>>>>>>>
>>>>>>> increase the power frequency to several megahertzc and you can push
>>>>>>> quite a bit through capacitors
>>>>>>
>>>>>> 2nF requires 80MHz to reach 1 ohm. Are you sure you want a kilowatt of
>>>>>> 80MHz just to save on magnetics?
>>>>>
>>>>> If you need a low cost, low power supply, the high frequency low capacity coupling idea is good.
>>>>>
>>>>> The limiting factor is, beyond EMC, the approval agency maximum "leakage" current over the barrier (for domestic is is often
>>>>> 0.5mA at 230V ac, so the capacitance must be below 6nF)
>>>>>
>>>>> Cheers
>>>>>
>>>>> Klaus
>>>>>
>>>>
>>>> Surely you risk RF burns doing this, besides all the cost and complexity
>>>> disadvantages.  You might not die from a bad RF burn the way you might
>>>> from 50/60 Hz, but you might wish you had. :(
>>>>
>>>
>>> RF burn?
>>>
>>> Where might that come from?
>>>
>>> The HF loop is closed. Square wave generator/buffer -> Two plate capacitors -> bridge rectifier -> Load. No HF escapes the loop,
>>> only low frequency mains leakage is running across the barrier
>>
>> Symmetry.
>
> Care to elaborate how dis-symmetry causes RF burns?
>
>> Ever worked with 1kW 80 MHz?
>
> No. I have worked with 8MW at 4.5kHz. Does that have anything to do with this??
>
> Regards
>
> Klaus
>

If there are no transformers, then each side of the bridge rectifier 
will be driven with a very stiff source of 80 MHz, ground referred, via 
a capacitor whose reactance at 80 MHz is small.  The output of the 
bridge will be connected alternately to the two phases of the RF, but if 
you touch the output, even in the most favourable case, you'll have many 
many volts of 160 MHz ripple current going through your body.  Grounding 
one side of the bridge output will produce some interesting fireworks.

At 60 Hz, with a transformer, the secondary winding's average voltage 
bounces up and down by half the p-p voltage, but since the inter-winding 
capacitance is small, this doesn't cause a lot of current to flow.

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

On Monday, December 1, 2014 11:35:18 AM UTC, John Fields wrote:
> On Sun, 30 Nov 2014 21:05:58 -0800, josephkk
> <joseph_barrett@sbcglobal.net> wrote:
> 
> >On Sat, 29 Nov 2014 01:41:26 -0600, John Fields
> ><jfields@austininstruments.com> wrote:
> >
> >>
> >>>The C in your circuit acts like a dropper or ballast, it doesn't give full isolation. Touch the load and you can still get a shock. Cs on both L&N give a load floating at half mains V, ground the load and i doubles.
> >>
> >>I disagree in that the shock can only occur if the toucher isn't
> >>floating, and since the capacitors' dielectric provides the
> >>insulation to prevent ohmic contact between the load and either side
> >>of the mains, the load is, by definition, isolated.
> >
> >I disagree.  Due to the possibly substantial currents that may flow
> >through the cap dropper it is not isolated.  Nor do i think that is within
> >the meaning intended by the NEC and regulators.

> I believe that, strictly speaking, "isolated" means that there's no
> ohmic path from the mains to the load, which is what the capacitors'
> dielectric assures, regardless of the current allowed through the
> load by the capacitors' reactances. 
> 
> Note also that even if direct contact is made - by a human, say -
> with mains hot, as long as there's no path from the human back to
> the other side of the mains, there'll be no shock hazard, no matter
> the meaning "intended" by the NEC and regulators.

Usually there's a path from human to earth/ground, which serves very effectively for shocking purposes.

> Not that it would be a good thing to leave exposed mains connections
> flying in the breeze, I'm just trying to make a point.


NT

On Sunday, November 30, 2014 8:41:18 PM UTC-8, rickman wrote:
> On 11/27/2014 3:12 PM, whit3rd wrote:
> > On Wednesday, November 26, 2014 9:22:06 PM UTC-8, daku...@gmail.com wrote:
> >
> >> A voltage transformer is used to provide
> >> galvanic isolation, in a power supply,
> >> amongst other features. Is there another
> >> way to achieve galvanic isolation ?
> >
> > Powered lamp, air gap, photovoltaic "solar panel"
> > Motor, belt/hydraulic pump/nonconductive shaft, generator
> > Buzzer, ceramic rod, contact-microphone-and-rectifiers
> > Hydrolysis apparatus, low-pressure gas tubing, fuel cell
> > Heat pump, circulating air or fluid, thermopile
> > Battery factory...
> 
> I like the last one.  Use the incoming power to enable a PC to 
> auto-trade in the stock market buying and selling making enough money to 
> buy a battery factory which produces a product to power the isolated 
> side of the interface after delivery by UPS... er, that's United Parcel 
> Service, not Uninterruptable Power Supply.  I don't think there is 
> anything uninterruptable about UPS the carrier.

  Compared to you, Rube Goldberg was a piker!


  Mark L. Fergerson

On 12/1/2014 8:42 PM, nuny@bid.nes wrote:
> On Sunday, November 30, 2014 8:41:18 PM UTC-8, rickman wrote:
>> On 11/27/2014 3:12 PM, whit3rd wrote:
>>> On Wednesday, November 26, 2014 9:22:06 PM UTC-8, daku...@gmail.com wrote:
>>>
>>>> A voltage transformer is used to provide
>>>> galvanic isolation, in a power supply,
>>>> amongst other features. Is there another
>>>> way to achieve galvanic isolation ?
>>>
>>> Powered lamp, air gap, photovoltaic "solar panel"
>>> Motor, belt/hydraulic pump/nonconductive shaft, generator
>>> Buzzer, ceramic rod, contact-microphone-and-rectifiers
>>> Hydrolysis apparatus, low-pressure gas tubing, fuel cell
>>> Heat pump, circulating air or fluid, thermopile
>>> Battery factory...
>>
>> I like the last one.  Use the incoming power to enable a PC to
>> auto-trade in the stock market buying and selling making enough money to
>> buy a battery factory which produces a product to power the isolated
>> side of the interface after delivery by UPS... er, that's United Parcel
>> Service, not Uninterruptable Power Supply.  I don't think there is
>> anything uninterruptable about UPS the carrier.
>
>    Compared to you, Rube Goldberg was a piker!

What?  I'm just describing a carrier based power delivery system like 
several others here... but with a different type of carrier.  ;)

-- 

Rick