Characteristic Curves - Siemens 3VA1 100 A Manual

Description
2.6 Protection system
2.6.2

Characteristic curves

To design a low-voltage switchboard in accordance with the valid rules, the system planner
needs to dimension the protection settings of the molded case circuit breakers.
The settings selected for the trip unit of a molded case circuit breaker depend on the type of
equipment to be protected, e.g. switchboard and applications.
Tripping characteristics up to a tripping time of ≥ 1 ms are represented graphically. In order
to ease the coordination of different protection devices, the current is specified as a multiple
of the current setting value and the time is specified in seconds.
Tripping characteristics for thermal-magnetic trip units
Characteristics are displayed graphically in the double-log coordinate system (cf.
IEC 60947-2, paragraph 4.7.4 and IEC 60269-1). The current : time ratio is 2 : 1.
Tripping characteristics for electronic trip units
Characteristics are displayed graphically in the double-log coordinate system (cf.
IEC 60269-1). The current : time ratio is 1 : 1.
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3VA molded case circuit breakers
Manual, 04/2015, A5E03603177010-02