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New generation IZM97, 99 low voltage air circuit breaker instruction manual
MN013010EN February 2020 www.eaton.com.cn
Section 3: Circuit breaker description and operation
3-2 Basic circuit breaker assembly
IZM9 circuit breakers use a rigid frame housing construction
of engineered thermoset composite resins. This construction
provides high-strength structural properties, excellent dielec-
tric characteristics, and resistance to arc tracking.
The three-piece construction approach provides support
while isolating and insulating power conductors.
A two-piece engineered thermoset composite resin case
encloses current paths and arc chambers. The chambers act
to channel arc gases up and out of the circuit breaker during
interruption.
The operating mechanism sits on the front of the case and is
electrically isolated and insulated from current contact struc-
tures. It is covered by an insulating front cover.
3-3 Operating mechanism
The IZM9 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 3-6). The mecha-
nism is a two-step stored energy mechanism. Potential ener-
gy is stored to close the circuit breaker. Sufficient energy
to open the circuit breaker remains available after a closing
operation.
Figure 3-5 Typical construction (right side view)
Figure 3-6 Electrically operated drawout circuit breaker with front cover removed
1
2
(Case)
(Front cover)
7
2
1
4
3
5
6
8
2
1
3
5
6
7
8
4
Secondary wiring points
Field installable accessories
(3 maximum)
Trip unit
Electric charging motor
Manual charge handle
Operations counter (optional)
Padlockable levering device
access door
Breaker position indicator
