DATE     96/11/20
    Opérateur BIOT
    --------------

    CHPO1 = BIOT |('POTE')|
                 |('INDU')|  GEO1  

                 |  'CERC'  CENTR1  POIN1 POIN2 RI RE H  |
                 |  'ARC'   CENTR1  POIN1 POIN2 RI RE H  |  
                 |  'BARR'  POIN1   POIN2 POIN3 DY DZ    |
                 |  'FIL'   POIN1   POIN2                |

                 ('TRAP' P1 P2) DENS  MU0     ;


    Description :
    ____________

    The BIOT operator constructs the Biot et Savart induction field 
 or vector potential created over the GEO1 object by
 a part of line, surface or massive inductor of rectangular (default) or
 trapezoidal cross section. It works only in 3D.


    Contents :
    __________

    'POTE' : vector potential calculation is required.
    'INDU' : induction calculation is required.
    GEO1   : geometrical object supporting the field to be computed
             (MAILLAGE type)

    The spiral can either be a closed circle, or an arc of a circle
 or a bar or else a wire, depending on the key word. Therefore the data are :


    'CERC' : key word followed by :
    CENTR1 : circle centre (POINT type)
    POIN1  | two points of the spiral plane (POINT type)
    POIN2  |
    RI     : spiral internal radius (FLOTTANT type)
    RE     : spiral external radius (FLOTTANT type)
    H      : spiral total height (FLOTTANT type)
        Remark : Using well-adapted values for RI, RE and H
                allows to model either a circular wire or circular
                current surfaces as well.
                        RI = RE et H = 0 : circular spiral
                        RI = RE et H > 0 : cylindrical surface
                        H = 0            : crown


    'ARC'  : key word followed by :
    CENTR1 : circle centre (POINT type)
    POIN1  | two points of the spiral plane (POINT type)
    POIN2  |
    RI     : spiral internal radius (FLOTTANT type)
    RE     : spiral external radius (FLOTTANT type)
    H      : spiral total height (FLOTTANT type)
        Remark : Using well-adapted values for RI, RE and H
                allows to model either a circular wire or circular
                current surfaces as well.
                        RI = RE et H = 0 : piece of circular spiral
                        RI = RE et H > 0 : piece of cylindrical surface
                        H = 0            : piece of crown


    'BARR' : key word followed by :
    POIN1  : centre of gravity of the initial section (POINT type)
    POIN2  : centre of gravity of the final section (POINT type)
    POIN3  : point defining the bar local axis oy (POINT type)
    DY     : bar width in the plane POIN1 POIN2 POIN3
    DZ     : bar width in the plane at 90 from the previous
        Remark : Using well-adapted values for DY, and DZ
                allows to model rectangular current surfaces.
                        DZ = 0 : rectangular surface lying in the plane xOy
                        DY = 0 : rectangular surface lying in the plane xOz




    'FIL'  : key word followed by :
    POIN1  : first extremity of the straight wire (POINT type)
    POIN2  : second extremity of the straight wire (POINT type)

    'TRAP' : key word used to define a trapezoidal cross section :
                In the circular case, we assume that the cross section
                lies in the plane (r,z) and that the parallele edges
                are along the z-direction of the rotation axis.
                In the linear case, we assume that the cross section
                lies in the plane (x,z) and that the parallele edges
                are along the z-direction. We can then define the slopes
                in the cross section local coordinates system.
    P1     : lower slope of the trapezoidal cross section (FLOTTANT TYPE)
    P2     : upper slope of the trapezoidal cross section (FLOTTANT TYPE)
                Remark : Using well-adapted values for P1, and P2
                allows to model either triangular cross section inductors  
                or conical part current surfaces as well.
                P1 = P2 and H = 0       : conical case (circular case)
                H = |P2 - P1|(RE-RI)/2  : triangular cross-section


    DENS   : current density (A/m2 in the massive case,
             A/m in the surfacic case,
             A in the linear case) in the inductor cross
             section (FLOTTANT type), considered positive as follows :

             - 'CERC' case : in the trigonometric direction connected
                             with CENTR1, POIN1, POIN2
             - 'ARC'  case : from POIN1 to POIN2
             - 'BARR' case : from POIN1 to POIN2
             - 'FIL ' case : from POIN1 to POIN2

    MU0    : vacuum permeability allocated to the unit of length
             used (FLOTTANT type)

    CHPO1  : induction field (CHPOINT type) of components BX BY BZ
             or vector potential (CHPOINT type) of components AX AY AZ,
             according to the corresponding key-word.