1.8. 33-790-11
6.2 STATIONARY CONTACT SUB-ASSEMBLIES
The stationary contact sub-assemblies may be seen
in
Figures 47, 48, 49,
51
and 53. All main contacts, i.e.
those which carry the main continuous load current, are
of
the butt type composed
of
a multiplicity
of
fingers.
Each finger is hinged at the upper end under controlled
pressure. Compression springs
at
the lower end apply
predetermined pressure against the moving main contact
in
closing, and standing
in
the closed position. These
springs are visible
in
the photograph
of
the DS206 only.
With this construction, the pressure
on
the main contact
surfaces is increased during the carrying and opening
of
Page 39
high short circuit currents because the magnetic field
of
the current pushes the lower end
of
the finger toward the
moving contact. Hinging the finger
at
the top thus results
in
what is sometimes called "blow-on" action. This greatly
increases the capability
of
the entire contact assembly to
withstand the high fault currents associated with these
breaker ratings.
The stationary arcing contacts are similar for all ratings
and consist
of
two parallel fingers, one
on
each side
of
the stationary terminal member. They are pushed toward
each other by compression springs and have arc resist-
ing tips.
'"'1·---------15.75
-------:l
rao-F~
I I I
1. Single Pole Unit
5.
Lo-•
Mein Terminal
9.
Main ContactS
2. Rigid Welded Frame·
6.
Upper
Main
Terminal
10. Moving Contact AsMrnblv
3. Molded Pole
Base
7. Stationary Contact Assemblv
11. Insulating Link Rod Ends
4.
Sensor
8. Arcing Contact
12. Moving Contect Pivot
Fig. 35 Three-Pole Assembly
of
DS-632 Pole Units
on
Frame
Effective October 1998
Courtesy of NationalSwitchgear.com
To Next Page
Loading...
