23
10/09 AWB1230-1605
Effective October 2009
Operation and maintenance of
IZM low voltage air circuit breakers
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Figure 26. Integral Arc Runner Viewed From Top of Arc
Chamber (Arc Chute Removed, Circuit Breaker Closed)
Arc chute
The IZM arc chute mounts down over the arcing contact. Alternating
V-shaped arc chute plates attract the arc and interrupt it. The top arc
plate, which is a part of the arc chute itself, also helps to attract the
arc away from the moving arcing contact and up into the arc chute’s
V-shaped plates (Figure 27).
Integral
Arc
Runner
Figure 27. IZM Arc Plate Assembly
Arc chute components are assembled in an insulating jacket that
is removable from the top of the circuit breaker, as previously
described in “Lifting circuit breaker” on page 9. Each arc chute
has a baffled top cover.
Electronic tripping system
The IZM circuit breaker uses a three-part tripping system
(Figure 28):
•
Microprocessor-based trip unit
•
Current sensors
•
Trip actuator
All three parts of the tripping system are discussed here, except that
the trip unit itself is not discussed in detail. For detailed information
pertaining to the different trip unit models available with IZM circuit
breakers, refer to the specific instruction leaflet dedicated to the trip
units (AWB1230-1608 and AWB1230-1609).
Top
“V”-Shaped Plates
“V”-Shaped Plates
Top Plate for
Arcing Contact
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