These circuit breakers protect plant from short circuits within the limits of their breaking capacity and by means of magnetic triggers (one per phase).
Magnetic circuit breaking is all-pole from the outset: one magnetic trigger will simultaneously open all the poles.
For low short-circuit currents, circuit breakers work faster than fuses.
This protection complies with the IEC 60947-2 standard.
To break a short-circuit current properly, there are three imperatives:
- early detection of the faulty current
- rapid separation of the contacts
- breakage of the short-circuit current
Most magnetic circuit breakers for motor protection are current-limiting
devices and so contribute to coordination.
Their very short cut-off time breaks the short-circuit current before it reaches its maximum amplitude.
This limits the thermal and electrodynamic effects and improves the protection of wiring and equipment.