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If the stranded coil’s current is known, it can be directly imposed in the cross-section of the stranded conductor. However, if the terminal voltage is specified in a given problem (e.g actuators) then the current is unknown.

In this situation the current must be deduced from the specified voltage, the number of windings and the coil’s total resistance. In our formulation, it is added as an unknown in the FEM/BEM system.

Since the source circuit becomes part of the FEM/BEM system, the EM_CIRCUIT_SOURCE must be associated to a *EM_MAT type 2 instead of type 1 in the imposed current case.

This case is a classic validation problem consisting of a voltage driven coil  (Constant voltage of 20V, resistance of 12.4 Ohms and 700 turns) between two conducting plates (sigma=3.28e7 Siemens). See VOLTAGE FORCED COILS FOR 3D FINITE-ELEMENT ELECTROMAGNETIC MODELS. P. J. Leonard and D. Rodger School of Electrical Engineering, University of Bath, Bath, Avon, BA2 IAY, U.K. IEEE TRANSACTIONS ON MAGNETICS, VOL. 24, NO. 6, NOVEMBER 1988.

Objective is to predict the coil’s current under the influence of the conducting plates.