Meaning
Ferromagnetic materials display a non-linear relationship between an applied magnetic field and the resulting magnetic flux density because internal magnetic domains resist realignment. A hysteresis loop tracks the path of this flux density as the external field strength increases to saturation and subsequently returns to zero. This closed curve represents the energy lost as heat when the material undergoes repeated cycles of magnetization and demagnetization.
Engineers rely on the area enclosed by this trace to determine the efficiency of magnetic cores in transformers and motors.
Magnetic Loss
Power conversion efficiency drops when the energy dissipated as heat increases within the core of an inductor. Magnetizing and demagnetizing a material forces atomic magnetic dipoles to overcome internal friction, which creates the heat quantified by the area of the curve. High frequency applications demand materials with narrow loops to prevent thermal runaway.
Designers select soft magnetic materials to minimize this characteristic energy penalty.
Measurement Method
Standard laboratory equipment uses a fluxmeter or an oscilloscope to plot the relationship between magnetic field intensity and induction. Current flows through a primary winding on a toroidal sample to generate the field while a secondary coil captures the induced voltage proportional to the rate of flux change. Integration of the secondary signal produces the vertical axis value while the primary current determines the horizontal axis value.
Technicians monitor these signals to identify the coercive force required to reduce residual magnetization to zero.
Material Characterization
Saturation points and retentivity define the operational limits of a core component. Materials with wide curves exhibit high retentivity, which makes them suitable for permanent magnets. Narrow curves describe materials that switch polarity with minimal resistance, which reduces operational costs in active power systems.
A wider loop indicates higher coercive force and greater resistance to field reversal.
