Dan Kinney asks about pole-to-pole hi-pot testing.
The hi-pot test determines that the product's
insulation (both air and solid) is sufficient to
withstand the normally-occuring transient over-
voltages on a power line. Transient over-voltages
are both differential-mode (pole-to-pole) and
common mode (both-poles-to-ground).
Some safety standards require two hi-pot tests:
pole-to-pole, and
both-poles-to-ground.
Some safety standards only require one hi-pot test:
both-poles-to-ground.
Pole-to-pole insulation is functional insulation.
That is, the insulation is used for the proper
functioning of the circuit. It does not provide
protection against electric shock. Pole-to-pole
insulation failure is mitigated by an overcurrent
device either in the building installation or in
the product itself.
Pole-to-ground insulation is a safeguard (i.e.,
basic insulation). That is, the insulation is
used for protection against electric shock
(although it may also serve a functional purpose).
Pole-to-ground insulation failure is mitigated by
a second safeguard, typically a grounded part or
a second, independent insulation.
Pole-to-pole insulation is comprised of the
insulation between the terminals of components,
and the insulation provided by the construction
of the conductors connecting the components to
the circuit.
Except for the terminal-to-terminal construction,
components are not considered insulation; rather,
they are impedances and therefore are not subject
to insulation requirements, i.e., the hi-pot test.
On the other hand, the wiring that connects the
components into a circuit does have pole-to-pole
insulation. The electric strength of this
insulation is determined by the product manufacturer
by means of the way in which the conductors are
designed and arranged, whether individual wires or
a printed wiring board or both.
The pole-to-pole hi-pot test is to determine that
the wiring -- independent of the components -- is
sufficient to withstand the differential-mode
over-voltages.
In some standards, pole-to-pole hi-pot testing is
not done in lieu of constructional requirements --
minimum physical distances through air (clearance)
and along the surface of solid insulation
creepage distance).
In yet other standards, pole-to-pole insulation is
not considered to affect the safety of the product
since the overcurrent device provides protection
in the event of failure of pole-to-pole insulation.
> circuitry is unaffected by the potential and thus is untested. Is the
> proper method then to lift the ground leg of the regulator and then work on
> down the line lifting each current conducting component to ground?
Yes. (Although, it doesn't make much difference
which leg is lifted.)
Best regards,
Rich
-------------------------------------------
This message is from the IEEE EMC Society Product Safety
Technical Committee emc-pstc discussion list.
Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/
To cancel your subscription, send mail to:
majord...@ieee.org
with the single line:
unsubscribe emc-pstc
For help, send mail to the list administrators:
Michael Garretson: pstc_ad...@garretson.org
Dave Heald davehe...@mediaone.net
For policy questions, send mail to:
Richard Nute: ri...@ieee.org
Jim Bacher: j.bac...@ieee.org
All emc-pstc postings are archived and searchable on the web at:
http://www.rcic.com/ click on "Virtual Conference Hall,"
