Hi Lauren:
The argument regarding the smaller cross-section
area due to the lock-washer construction does not
result in a higher bonding resistance. This is
because both pieces are relatively massive, and
do not overheat when subjected to the 25-ampere
fault current.
Some years ago, I reported on the value of
contact resistance under various conditions:
http://ewh.ieee.org/soc/pses/Downloads/newsletters/97v10n2.pdf
The use, or not, of a lock-washer in the
chassis connection is of no consequence to
the electrical performance of the connection.
However, to keep the connection tight, I
certainly recommend the use of a lock-washer!
Best regards,
Rich
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
[email protected]
Sent: Tuesday, June 09, 2009 10:20 AM
To: [email protected]
Subject: lock washer in ground conduction path.
There seem to be arguments for using a lock washer, particularly a star
washer, between a ring lug and a chassis connection point since it could
improve (lessen) the impedance of the circuit by breaking through surface
oxides and corrosion.
There are arguments against using lock washers in this manner, because
they
often have a smaller conductive cross-section than the ring lug itself and are
not otherwise rated for electrical service.
Does anyone know of any electrical design standard or authoritative
guidance
document that squarely addresses this question?
Of course, for the issue of mechanical stability, a washer can be
placed on
the top side of the lug, and so not participate directly in the conduction
path.
Lauren Crane
Product Regulatory Analyst
Corporate Product EHS Lead
Applied Materials Inc.
Austin, TX 512 272-6540 [#922 26540]
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