Computer-aided magnetic circuit design for a bell ringer

TLDR: A general computer-aided design method for use with electromagnetic devices such as ringers, relays, and solenoids is described and demonstrated by applying it to the design of polarized bell ringers to achieve major design improvements.

Abstract: A general computer-aided design method for use with electromagnetic devices such as ringers, relays, and solenoids is described. The method is demonstrated by applying it to the design of polarized bell ringers. A lumped-element model with electrical, magnetic, and mechanical portions is used in the analysis. First, interaction equations are derived using a Lagrangian formulation applied to a simple model. Second, the model is refined by subdividing the iron members and including more leakage paths. An electrical circuit analysis program assembles the equations for the electromagnetic portion of this more complete model and produces a subroutine that solves these equations. A computer program has been written to predict the effects of changing motor parameters. The versatility and usefulness of the design technique has been demonstrated by applying it to the Bell System TRIMLINE® telephone set ringer to achieve major design improvements.