The electromagnetic energy conversion is given by Ampere's law and Faraday's law respectively:
Vm = N * i N * dΦ/dt = -v
Vm is the magnetic potential difference applied to
the magnetic circuit due to the current i through the coil
(Ampere's law). There exists a left-hand assignment between the
current i (Put your hand around the coil, fingers pointing in the
direction of current flow.) and the magnetic potential difference
Vm (thumb).
Note: There exists a right-hand assignment between
the current through the coil i (fingers) and the magnetomotive
force mmf. The mmf has the opposite direction compared with
Vm, it is not used in Modelica.
For the complete magnetic circuit the sum of all magnetic
potential differences counted with the correct sign in a reference
direction is equal to zero: sum(Vm) = 0.
The magnetic flux Φ in each passive component is related to the
magnetic potential difference Vm by the equivalent of
Ohms' law: Vm = Rm * Φ
Note: The magnetic resistance Rm
depends on geometry and material properties. For ferromagnetic
materials Rm is not constant due to saturation.
Therefore the sign (actual direction) of Φ (magnetic flux
through the converter) depends on the associated branch of the
magnetic circuit.
v is the induced voltage in the coil due to the derivative of
magnetic flux Φ (Faraday's law).
Note: The negative sign of the induced voltage v
is due to Lenz's law.
Note: The image shows a coil wound counter-clockwise (positive mathematical direction). If a coil wound clockwise has to be modeled instead, the parameter N (Number of turns) can be set to a negative value.
The flux linkage Ψ and the static inductance L_stat = |Ψ/i| are calculated for information only. Note that L_stat is set to |Ψ/eps| if |i| < eps (= 100*Modelica.Constants.eps).