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Sent from my BlackBerry
From: Bill Owsley [mailto:[email protected]]
Sent: Saturday, May 11, 2013 02:21 PM
To: Boštjan Glavič <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: [PSES] safety 60950 and surge suppression circuits
Thanks !
A very clear answer. Not the one I wanted, but clear.
________________________________
From: Boštjan Glavič <[email protected]>
To: Bill Owsley <[email protected]>
Cc: "[email protected]" <[email protected]>
Sent: Saturday, May 11, 2013 12:29 PM
Subject: Re: [PSES] safety 60950 and surge suppression circuits
Hi Bill,
You can use MOV (VDR) primary to PE as long as you have reliable earth.
Reliable earth is considered for pluggable equipment type B or permanently
connected equipment. For pluggable equipment type A, you would need additional
earthing point, what is usually not acceptable for clients.
Unfortunately, if you use combination VDR + GDT, GDT needs to comply
with requirements for basic insulation (1500Vac) for any kind of equipment. I
know the requirement is strange but also new hazard based standard 62368-1 has
the same requirement.
GDT alone cannot use bridge basic insulation primary to PE.
But please note, this is valid for primary circuit only. For secondary
circuits no such requirements are applicable.
Best regards,
Bostjan
On 11. maj 2013, at 18:09, "Bill Owsley"
<[email protected]<mailto:[email protected]>> wrote:
I'm running into a dilemma. Not being a Safety Engineer myself, but
rubbing elbows with them...
On a piece of ITE equipment, I need some surge suppression for
worldwide markets with one annoying requirement for 4 kV, otherwise just 2 kV
line to earth, and using either plugable cords or permanent connection,
whichever is worse.
Now the Safety guys tell me that MOV's alone cannot bridge the
insulation (Basic or Functional, I forget.) between primary and earth, when
using one of power cable options mentioned above.
But a proper qualified (GDT) gas discharge tube can do the bridging.
So we figured to use them in series.
On a quick and dirty bench test it works to 4 kV.
Then the Safety guys pull out the rest of the story and point out 5.2.2
which seems to indicate that the GDT is to meet the Hi-Pot test, 1500 vac.
Previously, section, 1.5.9.4 (?) indicates that the surge protection
devices can be removed during the Hi-Pot test.
But now I have a Surge suppression circuit that has to withstand the
same Hi-Pot as the rest of the board.
Question is how does a surge protection circuit protect the board when
it has to meet the same Hi-Pot test?
In other words, when a surge comes along, which is going to break over
first?
The surge protection or the board?
Is the purpose of surge suppression is to keep the clamped voltage
below a problem level?
What am I missing in this?
Thanks...
- Bill
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