Hello from San Diego:
Eric Henning asks about clearance distances from an "insulated"
component to a grounded enclosure.
The issue is: What safety "class" is the insulation?
Insulation safety "classes" are:
Operational or functional (for functional purposes and which
is not considered to provide any protection against
electric shock)
Basic (for basic protection against electric shock)
Supplemental (for supplemental protection against electric
shock in the event of failure of basic insulation)
Double (a construction comprised of basic and supplemental)
Reinforced (a single, robust insulation equivalent to double
insulation)
Typically, component insulations are functional only. For the
purposes of safety, the insulation is ignored. So, the spacing
(clearance) from the component to the grounded enclosure would
be that spacing required for basic insulation.
Otherwise, the insulation on the component would need to be the
equivalent of a UL-Recognized insulation, i.e., pass all the
tests specified for a safety insulation.
I reviewed IEC 384 for X and Y capacitors. There are no
requirements for the insulating cover of these capacitors.
Consequently, the insulation cannot be relied upon as a safety
insulation.
While we are on the topic of component insulation, the spacings
must be measured AFTER the component is bent to its worst-case
position. Somewhere, in some safety standard, there exists a
requirement to verify internal spacings after the component has
been subjected to a specific force. Sorry, but I can't cite the
standard. If bending the component violates the spacing
requirement, then the component must be held in place such that
it cannot be bent over and reduce the spacing.
Best regards,
Rich
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Richard Nute Quality Department
Hewlett-Packard Company Product Regulations Group
San Diego Division (SDD) Tel : 619 655 3329
16399 West Bernardo Drive FAX : 619 655 4979
San Diego, California 92127 e-mail: [email protected]
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