Magnum
26
1812.900A
A functional local test of a major portion of the trip unit’s
electronic circuitry and the circuit breaker’s mechanical
tripping action can be verified through the trip unit’s test
receptacle (Figure 3-17). This is accomplished using a
Digitrip (DS Type) Test Kit which provides a secondary
injection test that simulates the current sensors. A small
hand held Magnum functional Test Kit can also be used to
check circuitry and mechanical tripping functions
(Figure 3-18).
When the circuit breaker is shipped from the factory, the
trip unit’s protective functions are normally set at
minimum values. For specific overload tripping
characteristics and time/current curves to coordinate with
a load or system, refer to the trip unit instruction book.
3.6.2 Rating
plug
All Magnum 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 2-4, Figure 3-17 and Table 3-3). 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
which is a function of the current sensor rating.
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 3-2 for a tabulation of the available rating
plugs.
Figure 3-17: Digitrip RMS1150 Programmable Trip Unit
Installed in MagnumCircuit Breaker
1. Pop Out Trip Flag
2. Auxiliary Power Module Port
3. Rating Plug
4. Test Receptacle
Figure 3-18: Hand Held Tester
3.6.3 Current
sensors
Three toroidally wound current sensors are installed at
the rear of the circuit breaker on the lower terminals
(Figure 3-19). 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.
1
3
2
4
