Electrical Schematic – Motor Protection – Against Short Circuit – Magnetic Circuit Breakers

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.