Eaton IZM20, Operation And Maintenance Instructional Manual

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Operation and maintenance of
IZM low voltage air circuit breakers
MOELLER www.moeller.net/de/support
10/09 AWB1230-1605
Effective October 2009
Electrically operated optional devices are available to automatically
close or trip a manually operated circuit breaker. An electrical spring
release is available to close a manually operated circuit breaker.
Two optional devices, a shunt trip, and an undervoltage release,
are available to automatically trip (open) a manually operated
circuit breaker. These optional devices can be installed easily in
the field. For more details on these devices, refer to “Accessory
devices” on page 34 in this manual.
An electrical operator that is used to charge the closing spring
automatically can be added to a manually operated circuit breaker
in the field. Manually operated circuit breakers are pre-wired to
accept this addition.
Electrical operation
For electrically operated circuit breakers, the springs are normally
charged through the use of an electrical operator ( Figure 24 ). The
springs can, however, be charged manually as just described in the
previous paragraph.
Figure 24. Electrical Motor Operator to Charge Closing Spring
Like the manually operated circuit breaker in the previous paragraph,
electrically operated circuit breakers can also be manually closed
and opened through the use of the front-mounted Manual ON and
Manual OFF buttons.
An electrically operated circuit breaker from the factory is also
equipped as standard with a spring release to close the circuit
breaker electrically. An optional shunt trip and undervoltage
release are also available to trip (open) an electrically operated
circuit breaker. Refer to “Accessory devices” on page 34 for more
details on both standard and optional devices.
Electrical Motor Operator
Anti-pump feature
The IZM circuit breaker has both mechanical and electrical anti-pump
features. If the circuit breaker is closed on a fault condition (and
trips open while the CLOSE signal is maintained), using either the
mechanical pushbutton or the electrical close coil, it will not make
another attempt to close until the close command is removed and
reapplied.
otee: N
If the close signal is applied prematurely (before the breaker is
completely charged and latched), the close command will be ignored
until it is removed and reapplied.
For electrical closing, a Latch Check Switch (LCS) option is available
(see “Plug-in electrical accessories” on page 34) that will block the
application of the electrical close command until the breaker is ready
to close.
Arc chambers
The IZM circuit breaker uses arc chambers to insulate and isolate
individual poles from one another, from the rest of the circuit
breaker, and from operating personnel. Arc chambers are molded
and integral parts of the circuit breaker frame. Enclosed within
each arc chamber is an arc chute that mounts over each set of
primary contacts.
After the main contacts part, any remaining current is driven to the
arcing contacts ( Figure 25 ). Magnetic action draws the arc to
the arc chute. As the arcing contacts separate, the moving arcing
contacts discharge into the arc chute plates while the integral arc
runner also helps to draw the arc into the arc chute ( Figure 26 ).
Figure 25. Cross-Section of Conductor and Arc Control System
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Top Arc
Plate
Integral Arc
Runner
Current
Flow
Current
Flow