High-Power Intrinsic Safety realized by 'c-i-s', the new concept of an intrinsically safe power supply

摘要

As a result of fundamental explorations, the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig introduces the active principle of a new powerful intrinsically safe power supply. Contrary to the ripple-free direct current used so far, the "c-i-s" principle is based on direct current which is superimposed by alternating quantities. In the simplest way this can be achieved by shorting a direct current source for short periods of time. While the conventional d.c. practice admitted powers up to approx. 2W (Division 1 und 2 Group B Hydrogen) for associated apparatus (basis: IEC 60079-11, IEC 60079-0), the method of superimposition with accordingly-defined alternating quantities enables an intrinsically safe effective power up to approx. 20W. Thus, the Intrinsic Safety "i" type of protection can advance into power ranges which so far had been confined to other - usually more expensive - types of protection (e.g. Flameproof Enclosure "d" IEC 60079-1 or Increased Safety "e" IEC 60079-7).