| CONTACTS OF MAIN
POLES
The poles of
the type N contactors (namely the antiarc devices, pressure springs, shape of
contacts, the movement's dynamics and arc chutes) have been carefully designed
so that the following features are achieved : Very low contact bounce; Relative brushing of
the contact's surfaces with the resulting self-cleaning effect; Low
probability of arc re-priming, even with current, voltage and inductance
particulary high; Regular wear of the contacts.
The poles of
the type N contactors are normally fitted with very hard copper contacts and
the application of sintered contacts is not needed. However, depending upon the
application, the following types of contacts are recommended: -
Cooper contacts: for every purpose
with breaking current up to 6-8 times lth and voltage up to 600V; -
Sintered contacts in silver-cadmium oxide:
for general purpose. Suitable where low and constant contact resistance is
required (Type S1). - Sintered contacts in
silver-tungstan : for an extremely high number of operations or for
voltages above 600V and with high breaking current, where a low contact
resistance is not needed. (Type S4).
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