Reliable threshold switch for railway signalling - has toroidal core with magnet compensating field generated by normal measuring current

摘要

The switch has a toroidal core with a control winding for h.f.d.c. timing pulses for the core alternate magnetisation with one or the other remanence state. There is an output winding to which a signalling device is connected through a transformer, which delivers a signal when output pulses are missing. A magnetisation winding carries a measurement current derived from the measurement current or voltage. The magnetisation winding (MW) is outside the core (RK) provided with at least one permanent magnet (M) whose field (PHI M) compensates the field (PHI S) generated in the core by a normal measurement current (JS). The application is esp. of interest for railway signalling systems where very reliable systems are required.