25
10/09 AWB1230-1605
Effective October 2009
Operation and maintenance of
IZM low voltage air circuit breakers
MOELLER www.moeller.net/de/support
Figure 29. Digitrip RMS 1150 Programmable Trip Unit Installed
in IZM Circuit Breaker
Figure 30. Hand-Held Tester
Rating plug
All IZM circuit breaker trip units use a fixed type rating plug. The
current rating of the rating plug must match the current rating
of the integrally mounted current sensors (Figure 29). The rating
plug performs several functions:
1. It tells the trip unit what the rating is of the current sensors.
A label on the front of the rating plug clearly indicates that the
rating plug and sensors must have the same rating.
2. It determines the maximum instantaneous setting that is a
function of the current sensor rating.
Pop-Out Trip Flag
Auxiliary Power
Module Port
Rating Plug
Test Receptacle
3. When it is required that the maximum ground fault pickup
value not exceed 1200 amperes, a properly matched rating plug
accomplishes this requirement for higher ampere sensors by
incorporating circuitry to identify that level by sensor rating.
If the rating plug is removed from the trip unit, the circuit breaker
will trip if it is carrying current. Make certain the rating plug is
secured in position with its retaining screw. Do not torque the
retaining screw beyond 0.1 Nm.
Refer to Table 5 for a tabulation of the available rating plugs.
Current sensors
Three toroidally wound current sensors are installed at the rear of
the circuit breaker on the lower terminals (Figure 31). The sensors
produce an output current proportional to the load current. Under
preselected conditions of current magnitude and time, the sensors
furnish the trip unit with a signal and the energy required to trip the
circuit breaker.
External neutral current sensors are also available for customer
installation. The additional sensor is not supplied with the circuit
breaker and must be ordered separately. They are wired to the trip
unit through the secondary contacts of the circuit breaker.
Refer to Table 5 for a tabulation of the available current
sensor ratings.
Figure 31. Replaceable Current Sensors Shown with Bottom
Adapters and Cover Plate Removed
Table 5. IZM Current Sensors and Matching Rating Plugs
Current Rating in Amperes
200 1000 –
250 – 3200
300 1250 4000
400 1600 5000
– 2000 6300
630 2500
800 3000
Toroidal
Sensor
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