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'[EE] Diodes in serie: breakdown voltage'
2011\11\22@130028 by Electron

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Hello,
if I need a 5KV silicon rectifier diode, will using five 1KV silicon rectifier
diodes in serie grant me the safety I'm looking for, or it won't work in real life?

Thanks!
Mario

2011\11\22@130626 by Carey Fisher

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Why not just buy a 6000V diode from: <http://www.amazing1.com/capacitors.htm
>

*6000 Volt at 5ma*   .3 x .12" epoxy coated cylinder
*Quantity*
  *VG6* - High Volt Diode............*$1.95*

On Tue, Nov 22, 2011 at 12:59 PM, Electron <spam_OUTelectron2k4TakeThisOuTspaminfinito.it> wrote:

>
> Hello,
> if I need a 5KV silicon rectifier diode, will using five 1KV silicon
> rectifier
> diodes in serie grant me the safety I'm looking for, or it won't work in
> real life?
>
> Thanks!
> Mario
>
>

2011\11\22@132720 by Bob Ammerman

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> Hello,
> if I need a 5KV silicon rectifier diode, will using five 1KV silicon
> rectifier
> diodes in serie grant me the safety I'm looking for, or it won't work in
> real life?
>
> Thanks!
> Mario

This can be made to work by placing high-resistance resistors in parallel with each diode. This will, of course, increase leakage by quite a bit, but the resistors will help ensure that the reverse voltage is evenly spread across the diodes. I would probably use a longer chain than 5 diodes to allow for unequal voltage division even with the resistors.

Of course, the prior post's recommendation of using a single high-voltage diode makes plenty of sense.

-- Bob Ammerman
RAm Systems

2011\11\22@133218 by alan.b.pearce

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> Hello,
> if I need a 5KV silicon rectifier diode, will using five 1KV silicon
> rectifier diodes in serie grant me the safety I'm looking for, or it
> won't work in real life?

No, you need a voltage balancing network across each diode to ensure you don't exceed the voltage of individual diodes.

As Carey Fisher said, you are better off with a single diode that meets the requirements.


-- Scanned by iCritical.

2011\11\22@145100 by Spehro Pefhany

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At 12:59 PM 22/11/2011, you wrote:

>Hello,
>if I need a 5KV silicon rectifier diode, will using five 1KV silicon rectifier
>diodes in serie grant me the safety I'm looking
>for, or it won't work in real life?
>
>Thanks!
>Mario

Most high voltage rectifiers are composed of stacked diodes
internally. Reverse breakdown of a Si diode is not like
dielectric breakdown (as a MOSFET gate or other insulator)-- it
is reversible, has no negative resistance characteristic, and
does not inherently cause damage to the diode (unless the current is
high).

What will happen is that the voltage (say 5kV) will distribute itself
across the chain so that the leakage currents are equalized. If you
used, say, 1N4007 diodes, one diode might have 1.1kV and the next 0.9kV,
but the total reverse current should not exceed a couple hundred nA
at 25°C. Of course if one diode fails short and the current is not
limited externally, the others will likely go as well. Using six
would give a bit of margin.

See this commercial HV rectifier, for example:
http://www.hvpsi.com/pdf/D0458ser.pdf

The standard recovery rectifiers have a Vf of 1V per kV of reverse
breakdown rating @1A.

Similarly, common microwave oven diodes have Vf of around 8-14V
and reverse voltage ratings of 8-12kV.

Or the Rectron R5000F is ~75 cents in singles and good for 0.2A at
5kV (Vf of 6.5V at 0.2A)

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
.....speffKILLspamspam@spam@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com


2011\11\22@193303 by RussellMc

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> See this commercial HV rectifier, for example:
> http://www.hvpsi.com/pdf/D0458ser.pdf

They seem to use an unusual value for "Radial"


                    Russel

2011\11\22@203141 by Spehro Pefhany

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At 07:32 PM 11/22/2011, RussellMc wrote:
> > See this commercial HV rectifier, for example:
> > http://www.hvpsi.com/pdf/D0458ser.pdf
>
>They seem to use an unusual value for "Radial"
>
>                      Russell

How so? IME, if it's not axial, it's usually called "radial".

But it _is_ a bit strange, now that you mention it. The centre/center of
that radius must be a long way off.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspamKILLspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

2011\11\23@060348 by Electron

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Thanks.. this list is wonderful, how many things do I learn every day here?

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