# Voltage Driven Coil — Welcome to LS-DYNA Examples

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This example shows a stranded coil problem that is voltage driven rather than having an imposed current. For voltage driven coils, the voltage, the number of turns as well as the coil’s resistance must be provided. Since the current is an unknown, the EM material must be defined as type 2 for the coil become part of the system. This case is a validation problem first proposed by Leonard & Rodger.

## Description

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.

## Keywords

```*EM_CIRCUIT_SOURCE
*EM_CONTROL
*EM_CONTROL_COUPLING
*EM_CONTROL_TIMESTEP
*EM_MAT_001
*EM_MAT_002
*EM_OUTPUT
*EM_SOLVER_BEM
*EM_SOLVER_BEMMAT
*EM_SOLVER_FEM
*EM_SOLVER_FEMBEM_MONOLITHIC
```

## Reduced Input

```*KEYWORD
\$ ****************************************************************************
\$ electromagnetism
\$ ****************************************************************************
*EM_CONTROL
\$--------1---------2---------3---------4---------5---------6---------7---------8
\$    emsol     numls        dt
1
*EM_CONTROL_TIMESTEP
\$#  tstype    dtcons      lcid
1    &em_dt
*EM_SOLVER_FEM
\$--------1---------2---------3---------4---------5---------6---------7---------8
\$   reltol   maxiter     stype    precon   uselast  ncyclfem
1.e-7     10000         1         1         1      5000
*EM_SOLVER_BEM
\$--------1---------2---------3---------4---------5---------6---------7---------8
\$   reltol   maxiter solvetype    precon   uselast  ncyclbem
1.e-7     10000         2         2         1      5000
*EM_SOLVER_FEMBEM_MONOLITHIC
\$--------1---------2---------3---------4---------5---------6---------7---------8
\$   reltol   maxiter    forcon
\$     1.e-4       100                             3
,,1.e-14,1.e-5
*EM_SOLVER_BEMMAT
\$--------1---------2---------3---------4---------5---------6---------7---------8
\$    matId                                                                relTol
1                                                                1.e-12
*EM_SOLVER_BEMMAT
\$--------1---------2---------3---------4---------5---------6---------7---------8
\$    matId                                                                relTol
2                                                                1.e-12
*EM_SOLVER_BEMMAT
\$--------1---------2---------3---------4---------5---------6---------7---------8
\$    matId                                                                relTol
3                                                                1.e-12
*EM_CONTROL_COUPLING
,2
*EM_CIRCUIT_SOURCE
\$--------1---------2---------3---------4---------5---------6---------7---------8
\$   circid  circtype      lcid         R         L         C
2         2       333  &resCoil    &Turns
\$  sidcurr    sidvin   sidvout    partID
187                           185
*EM_MAT_002
\$--------1---------2---------3---------4---------5---------6---------7---------8
\$      mid     mtype     sigma     eosid     murel     eosmu
1         4&sigmaCoil         0    &murel
*EM_MAT_002
\$--------1---------2---------3---------4---------5---------6---------7---------8
\$      mid     mtype     sigma     eosid     murel     eosmu
2         4 &sigPlate         0    &murel
*EM_MAT_001
\$--------1---------2---------3---------4---------5---------6---------7---------8
\$      mid     mtype     sigma     eosid
3         4 &sigPlate
*EM_OUTPUT
\$--------1---------2---------3---------4---------5---------6---------7---------8
\$     matS      matF      solS      solF      mesh    memory    timing d3plotAsc
2         2         2         2         0         0         0         0
\$      mf2       gmv d3plotFor  timeHist
0         0         0
*END```