3VA molded case circuit breakers with UL and IEC certification
Manual, 01/2019, L1V30435333-01
479
Method of remote operation of the motor operators via control cables, e.g. PLC.
The breaking capacity is the rms value of the current at a specific cos φ (power factor) and a
specific voltage which can be safely interrupted by a switching device or fuse under
prescribed conditions. The rms value of the symmetrical component applies in the case of
alternating current.
The I
2
t characteristic is a curve that represents the minimum or maximum values of I
2
t in
relation to break times as a function of the prospective current under defined operating
conditions.
The I
2
t value is the thermal value of a prospective or limited short-circuit current (let-through
current).
The let-through current
I
D
is the maximum instantaneous current value during the breaking
time of a switching device or fuse. Limited short-circuit currents occur if the switching device
reduces the amplitude of the short-circuit current due to, for example, resistance, switching
delay and peak arc voltage. The let-through current of a device such as a current-limiting
fuse or a current-limiting molded case circuit breaker determines the thermal load (
I
2
t value)
imposed on equipment connected downstream of the device (current limiting).
Operating mode of motor operators; the operator is locked and cannot be operated.
The making capacity is the value of the prospective making current which the switching
device can safely conduct at the instant of closing under prescribed conditions for a specific
circuit.
For molded case circuit breakers, the making capacity is expressed as the maximum
possible instantaneous value of the potential prospective current at the input terminals for
the specified voltage.
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