Delayed operation magnetically operated overcurrent relay - uses cylindrical inertia wheel to slow passage of operating arm when overcurrent occurs

摘要

Within its protective casing, the relay has a carrier and a magnetic core which is energised by a coil carrying the current being monitored. A pulsed vane is attracted by the magnetic core against the force of a spring. The rest position of the vane can be modified to adjust the current required to attract the vane to the core and thus initiate the operation of the circuit breaker. To delay the operation of the relay a cylindrical rotating inertia block is held in its rest position against a fixed stop by a restraining spring so as to present a driving surface to an arm extending from the vane. As the vane is drawn down by the core the arm contacts the driving surface, requiring that the inertia cylinder be displaced sufficiently for the vane to clear the driving surface if operation is to be completed.