During the mid-1970`s the RCCB market had to face a new challenge to extend the range of protection:Equipment containing half wave rectifiers and phase control modulators had to be included. However standard AC type RCCBs could not react to unipolar current with reasonable sensitivity due to rather high values of remanence induction BR . In Consequence a magnetic material with new properties had to be developped in order to guaranty person`s safety.The breakthrough came from a heat treatment in a strong magnetic field standing parallel to the axial direction of the core. By this the remanence value was reduced and this was the basis for a new generation and class of pulse current sensitive RCCBs. This advancement strenghened VAC`s position as the market leader.
A ULTRAPERM 10® core with round BH loop ("R"-loop) is without applied primary differential current magnetized to a relatively high B value (Br: Point of Remanence). This property is responsible for rather limited residual flux density swing in case of a unipolar fault current (light blue hatched area). These cores thus can only be used in RCCB application for alternating current. In consequence a way had to be found to increase the flux density swing by lowering the remanence induction.
The solution of the problem was the generation of a flat and linear hysteresis loop by means of annealing in a strong magnetic field perpendicular to the ribbon axis. The preliminary summit in material development actualy is represented by the nanocrystalline material VITROPERM 800 F®. For the flat-loop magnetization of this material see below. The remanence is nearly completely eliminated and so the material reaches a saturation flux density, which is higher by a factor of 1.5 than its crystalline 80% NiFe predecessor. This VITROPERM 800 F® core material is ideal for both unipolar pulsed-current applications and standard 50/60 Hz alternating current applications.
By combining material expertise and application knowledge, VAC provides technically superior and cost-effective solutions to the world. Such solutions made widespread use of Residual Current operated Circuit-Breaker possible in households.
back to First Stage of Development
Residual Current Circuit-Breaker
Letztes Update : 02.07.2012