21
10/09 AWB1230-1605
Effective October 2009
Operation and maintenance of
IZM low voltage air circuit breakers
MOELLER www.moeller.net/de/support
Figure 21. IZM97 and IZM32 (12-Finger) Moving
Conductor Assembly
Primary stationary contacts
The primary stationary contact is a combination of two items
(Figure 22). One is a conductive pad mounted on the line
conductor that functions as the stationary main contact. The
other is an arc runner, also connected to the line conductor.
The integral arc runner serves a dual purpose:
•
Fixed arcing contact
•
Part of the arc chute
Figure 22. Partial Cross-Sectional View (Shown in
Closed Position)
“Toe”
(arcing contact)
“Heel”
(main contact)
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Breaker Front
Breaker Bottom
Arc
Chute
Moving
Contact
Fingers
Moving
Contact
Springs
Integral Arc
Runner
Arcing Contact
(toe)
Line Conductor
Current
Flow
Stationary
Main Contact
Moving Main
Contact (heel)
Current
Flow
Operating mechanism
The IZM operating mechanism is based on the proven cam and
spring design. It is easily accessed by removing four cover screws
and the front cover (Figure 23). The mechanism is a two-step stored
energy mechanism. Potential energy is stored to close the circuit
breaker. Sufficient energy to open the circuit breaker remains
available after a closing operation.
Figure 23. Electrically Operated Drawout Circuit Breaker with
Front Cover Removed
Manual operation
On manually operated circuit breakers, the closing spring can only be
charged manually. To manually charge the spring, insert one finger
in the recess behind the charging handle and pull out. This permits
a gloved hand to grasp the handle and begin charging. It takes from
five to seven downward strokes on the charging handle to complete
the manual charging process. It is possible to manually recharge the
spring immediately after closing the circuit breaker and before it has
been tripped open.
Standard manually operated circuit breakers are closed and opened
by hand using the Manual ON and Manual OFF buttons respectively
located on the front of the circuit breaker (Figure 17). Performing
either operation is accomplished by pressing and releasing the
appropriate button. Access to these pushbuttons can be limited
by the use of an optional, padlockable cover. In addition, complete
access to the ON button can be prevented with an optional prevent
close cover. The status of the springs and the primary contacts is
always indicated in an indicator window just above the pushbuttons.
1–Secondary Wiring Points
2–Field Installable Accessories (3 maximum)
3–Trip Unit
4–Electric Charging Motor
5–Manual Charge Handle
6–Operations Counter (optional)
7–Padlockable Levering Device Access Door
8–Breaker Position Indicator
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