Improvements in Relays for the Protection of Electric Circuits.

摘要

20,095. Edgcumbe, K., and Everett, E. I. Sept. 9. Switches; cut - outs. - In relays of the electric motor type employed for the protection of distribution systems, means are employed to adjust the current of the motor so as to admit of the same timing scale being used with different overloads or reversals. The time - element depends upon the distance through which a weight or the like has to be wound up before relay contacts are closed or a tripping catch is released. The invention is shown embodied in an overload relay of the induction motor type for alternating currents. The motor is wound with a coil fed from a current transformer, and has a disk k steadied by a permanent magnet m and capable of turning on its spindle g, thus winding up a card f attached at one end to a weight f2 and at the other end to a beam a, which may be provided with a sliding weight for varying its resistance to movement. To set the time-element of the relay, the end of the beam is adjusted relatively to a scale i by a screw h. The spindle of the beam a carries carbon contacts d adapted to meet fixed contacts e. The card f slips on its spindle g after the contacts have met, so that chattering is prevented ; the contacts d are also mounted on a pivoted frame d', to render them self-alining with the contacts e. To adjust the current in, and hence the torque of, the motor, the coil l is provided with a series of graduated shunts, the terminals of which are arranged as a row of sockets p on a board o. A removable plug o' allows any one of the shunts to be completed. Resistances, shunts, condensers, or reactances may be employed. The invention may be applied to reverse-current relays of the induction motor type, and in general to automatic circuit-breakers, either for direct or alternating currents, operated by any type of electric motor.