Numerical modelization of transient current in relay

The authors describe the application of software for magnetic-field computation to the evaluation of transient current in the coil of a relay. The AZIMUT software package is used to compute the induced current in the coil and the electromagnetic force acting on the mobile part of the relay. This force is introduced in a simple mechanical equation to determine the change of position of the mobile part. The software has been modified to take into account the electromotive force induced by the movement. Some of the difficulties met in coupling the mechanical and electrical problems are discussed. The current measured in a relay fed with a voltage step is then compared to a computed curve. The shapes of the curves are similar. Several reasons for the differences between them are suggested