GB407780A - Improvements relating to the reduction of sparking at contacts in making and breaking electric circuits - Google Patents

Abstract

407,780. Sparking - preventing in switches; light-current relays. SIEMENS BROS. & CO., Ltd., Tothill Street, London, and EDWARDS, H. J., 5, Summerhill Road, Dartford, Kent. Nov. 14, 1932, No. 32186. [Class 38 (v).] In order to minimize sparking at the contacts when light-current relays of the type used in communication are used to control currents at voltages of the order of power systems, as in traffic signalling systems, the relay load contacts are associated with other contacts adapted temporarily to connect a condenser across the relay load contacts, the control of the other contacts being so effected that a delay is introduced between the opening of the load contacts and the condenser contacts. In Figs. 1, 2, the relay contacts a<1> control the load circuit pl and are shunted by a condenser QA and contacts b1 forming a circuit having a minimum of resistance. When a1 are to be closed, the armature A is arranged first to close b1 to complete the shunt circuit through QA, and when a1 open, they are protected by QA which is subsequently disconnected by the opening of b1. Alternatively, b1 may be controlled by a relay which may be either rendered sluggish in action, Fig. 3 (not shown) or controlled by a contact which is opened by the relay controlling a1, Fig. 4 (not shown). The contacts b1 may alternatively be themselves shunted by a similar protective condenser and contacts, Fig. 5 (not shown). In Fig. 6, the contacts a1 close first so that QA is not charged when b1 close. The charge acquired between the opening of a1 and the subsequent opening of b1 is dissipated in a resistance YA, thus protecting a1 against sparking when they are closed. In another form, Fig. 7 (not shown), the resistance is connected in circuit only after b1 have opened. The invention is also shown in its application to a system wherein several relays have a common condenser and set of spark-taking contacts controlled by a relay, Fig. 8 (not shown).