ABSTRACT
There are two force functions commonly encountered in magnetics: magnetomotive force, mmf, and magnetizing force, H. Magnetomotive force should not be confused with magnetizing force; the two are related as cause and effect. Magnetomotive force is given by the equation:
mmf=0.4πNI, [gilberts] [1-
Where, N is the number of turns and I is the current in amperes. Whereas mmf is the force, H is a force field, or force per unit length:
[17]
Substituting,
[18]
Where, MPL=magnetic path length in cm. If the flux is divided by the core area, Ac, we get flux density, B, in lines per unit area:
[19]
The flux density, B, in a magnetic medium, due to the existence of a magnetizing force H, depends on the permeability of the medium and the intensity of the magnetic field:
B=µH, [gauss] [1-
The peak, magnetizing current, Im, for a wound core can be calculated from the following equation:
[111]
Where Ho is the field intensity at the peak operating point. To determine the magnetizing force, Ho, use the manufacturer’s core loss curves at the appropriate frequency and operating flux density, Bo, as shown in Figure 1-25.
