Residual Current Circuit Breakers FI, NFI
- Isolating function
- Additional colour display of the position of main contacts (red – contacts closed, green – contacts open)
- A terminal shape prevents connection of a conductor outside the connection area
- Type A (designated NFI) – sensitive to alternating and pulsating dc residual operating currents
- Type AC (designated FI) – sensitive only to alternating residual operating currents of a sine wave form
- Type F (designated NFIF) – tripping is ensured as for type A and in addition for residual currents with mixed frequencies that can result from single-phase electrical loads with frequency inverters.
- Type B (designated NFIB) – tripping is ensured as for type A and in addition for smooth d.c. residual currents, residual d.c. currents which may result from rectifying circuits and high frequency a.c. residual currents.
- Type S: A switch with a delayed break enabling selectivity regarding a general type and a short-time delayed type (type G) connected on the load side
- Type G: a short-time delayed breaking characteristic (a min. non-actuating period is 10 ms)
- FIR-FIT combination: It is used for a protection in circuits where operational currents are higher than rated currents of residual current circuit breakers.