Condition control circuit for electrical fuse - has bistable switching auxiliary circuit in parallel operating indicator supplied from separate current source

摘要

The circuit, e.g. for a cartridge enclosed on all sides, indicates the state of the fuse to be monitored independently of the potential remaining on the safety conductor. This is achieved without mechanical switching or the necessity of a further connecting lead. The circuit is excited within an a.c. voltage period. After excitation it delivers a continuous indicating signal and is separated from one side of the monitored lead. An auxiliary safety circuit, in parallel with the main one, has a bistable switch which, when the main circuit is activated, operates an indicator fed from a separate current supply. The auxiliary circuit itself then operates. A threshold current valve (11) is in an auxiliary current circuit in series with the auxiliary fuse (9). The voltage impulse appearing across the valve (11) when the main fuse (2) operates is conducted via resistors (8,13) to the bistable switch formed by semiconductor switches (T1,T2).