Thermally delayed overcurrent relay - has instantaneous electromagnet tripping device combined with thermomagnetic material trip which gives delayed tripping

摘要

The functions of the thermally delayed tripping, of the instantaneous tripping and of trip-free release are combined in a rotatable, trippable or spring supported armature (3) which closes a magnetic circuit divided in two branches and excited by a permanent magnetthe flux in one of the branches flows through a thermomagnetic element (4) directly or indirectly heated by the current to be monitored the armature is in addition excited by a coil (5) carrying the monitored current, so that when the temperature of the thermomagnetic material exceeds its critical temperature, or owing to the electromagnetic excitation by very high currents, magnetic pull on the armature by the other branch prevails and throws the armature to its working position, in which it operates a contact (7)only after a certain cooling time.