Magnetiseringsstroom

Magnetiseringsstroom, or magnetizing current, is the current required to establish the magnetic flux in the core of a magnetic device such as a transformer or inductor when it is energized. In normal transformer operation with no external load, the input current is dominated by this magnetizing current, which serves to create the magnetic flux Φ in the core according to the relation V = N dΦ/dt.

The magnetic circuit presents reluctance, so a magnetizing inductance Lm characterizes the voltage–current relationship. For a given core, I ≈ V / (ωLm), where ω is the angular frequency. In practical transformer models, the magnetizing branch is often represented as an inductance Lm in parallel with a core-loss resistance Rc, which accounts for hysteresis and eddy-current losses. The inductance can be expressed as Lm = N^2 / Rm = μ0 μr N^2 A_e / l_e, with N turns, A_e the effective cross-sectional area, and l_e the magnetic path length.

Magnetiseringsstroom is mainly reactive, with a small resistive component due to core losses. Its magnitude depends on applied voltage, frequency, number of turns, and the core material and geometry. Higher permeability cores and more turns increase Lm and reduce the no-load current for a given voltage, while lamination and proper material selection reduce eddy-current losses and thus the active component of the current.

In summary, magnetiseringsstroom is the no-load current that establishes core flux; it is a key factor in transformer efficiency and is influenced by core design, materials, frequency, and operating voltage.