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→13.4.2.4 Switching Capacity
====13.4.2.4 Switching Capacity====
The main requirement for low voltage power switches is the withstanding of high short circuit currents. The short circuit switching capacity of power switches is determined in tests according to IEC/EN 60947-2 <xr id="tab:Testing for the Short Circuit Breaking Capacity of Low Voltage Power Switches According to IECEN 60947-2 (Shortened Summary)"/> (Tab. 13.3). These test differentiate between the maximum short circuit current switching capacity (ultimate current limit) I<sub>CU</sub> and the operational (or service) short circuit current capacity I<sub>CS</sub> .
When specifying I<sub>CU</sub> it must be guaranteed that short circuit current up to the maximum limit value can be interrupted safely. After its occurrence it must be possible to switch on one additional time onto the not yet eliminated short circuit and again interrupt this short circuit current again safely. The switch does not have to be functional any more after this second interruption. A switch specified for I<sub>CS</sub> must still be capable to protect the circuit and be further usable within certain limitations.
