Siemens 3VA1 100 A, Manual

Page: 519 / 532

3VA molded case circuit breakers
Manual, 04/2015, A5E03603177010-02
519
Glossary
AUTO
Method of remote operation of the motor operators via control cables, e.g. PLC.
Breaking capacity
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.
I
2
t characteristic
The
I
2
t characteristic is a curve which represents the minimum or maximum values of
I
2
t in
relation to breaking times as a function of the prospective current under defined operating
conditions.
I
2
t value
The
I
2
t value is the thermal value of a prospective or a limited short-circuit current (let-
through 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).
LOCK
Operating mode of motor operators; the operating mechanism is locked and cannot be
operated.