1. Function
Protection of circuits against short-circuit currents.
protection of circuits against overload currents.
Switch.
Isolation.
Circuit-breakers are used in domestic installation, as well as in commercial and industry electrical distribution systems.
2. Selection
Technical data of the network at the point considered:
The earthing systems (TNS, TNC).
Short-circuit current at the circuit-breaker installation point, which must always be less than the breaking capacity of the device.
Network normal voltage.
Tripping curves:
B curve （3-5In）
Protection for people and big length cables in TN and IT systems.
C curve (5-10In)
Protection for resistive and inductive loads with low inrushcurrent.
D curve(10-14In)
Protection+for+circuits+which+supply+loads+with+high+inrush+current+at+the+circuit+closing
(LV/LV+transformers,+breakdown+lamps).
