Siemens 3VA1 100 A, Manual

Page: 523 / 532

Glossary
3VA molded case circuit breakers
Manual, 04/2015, A5E03603177010-02
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Rated uninterrupted current
The rated uninterrupted current
I
U
of a switching device, e.g. a molded case circuit breaker,
is a current that the device can conduct in uninterrupted operation (for weeks, months or
years). This current is specified by the manufacturer.
Rating
The rating is the power that a switching device is capable of switching at the associated
rated operational voltage in accordance with the utilization category, e.g. power contactor
utilization category AC-3:37 kW at 400 V.
Remote control
Or AUTO; method of remote operation of the motor operators via control cables, e.g. PLC.
Short circuit
Connection with a negligibly low impedance between two points of different potential in an
electric circuit. The short-circuit current is a multiple of the rated operating current. Short
circuits can cause thermal or mechanical damage to switching devices and other parts of an
electrical installation.
Short-circuit strength
This is the resistivity of a switching device in the closed state, along with its components
(e.g. trip units), or a complete switchboard to the electrodynamic and thermal stresses which
arise in the event of a short circuit.
The characteristic for the dynamic stress is the rated peak withstand current, which is the
maximum instantaneous value of the short-circuit current.
The characteristic for the thermal stress of the short-circuit current is the root-mean-square
value of the short-circuit current throughout its duration.
Tripping current of overload release
The current value at which a trip unit trips within a specified time.
Tripping current, ground fault
When the ground fault current reaches or exceeds this limit value, the ground-fault
protection, for example, of a molded case circuit breaker, is tripped.
Tripping current, instantaneous
When this current limit is exceeded, the circuit breaker trips instantaneously.