http://www.ieee-pses.org/symposium
http://www.emc2004.org/
> Across the secondary winding of a DC/DC converter transformer powering an
> un-earthed SELV load, we have a 75V peak 350KHz square wave at 75VDC input.
> One side of the winding is connected to the un-earthed SELV ground and the
> other side is switched by transistors and goes through an inductor to
> produce an SELV power voltage. We also have a snubber circuit with a
> capacitor charged at about 90VDC and connected to the same SELV ground.
>
> If there is no risk the SELV output would exceed SELV limits in the event
> the insulation would fail across components, do we still need Basic
> insulation across the components and between the components and the SELV
> ground or can we apply Functional insulation ?
>
> If we provide the required category of insulation could we still run into
> certification issues because we have hazardous voltages not "truly"
> insulated from the SELV power output due to active components bridging the
> insulation ? If yes, could a reliable crow-bar, such as a TVS diode across
> the output, solve the issue ?
Mr. Ivan Vandewege will be presenting a paper on this
subject at the 2004 IEEE PSES Symposium. I believe you
will find the answers to your questions in his paper!
"Safeguarding against hazardous voltages generated
within and not isolated from SELV circuits."
Best regards,
Richard Nute
Chairman, Technical Program
2004 IEEE PSES Symposium
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