Operation of an Electromagnetic Trigger with a Short-Circuit Ring

D. Križaj[1], Z. Top?agi?[1], B. Drnovšek[1]
[1]Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia

Numerical simulation of an electromagnetic trigger with a short-circuit ring is presented. The main goal of inclusion of a short-circuit ring in an electromagnetic trigger is to develop an element suitable for use in a circuit breaker with capabilities of selective switching. The main problem to be solved is vibration of a moving contact due to zero electromagnetic force between the anchor and the core at zero driving current. Inclusion of a short-circuit ring into the core results in induction of current in the ring during flux change. This current produces magnetic field that superimposes onto the main field and results in non-zero force between the anchor and the core during zero driving current in the windings. Numerical simulation reveals that inclusion of a short circuit ring does not significantly decrease the maximal force and that it effectively reduces vibrationy of a moving contact.