Iron-core inductor in the time-dependent case

The study of iron-core coils in variable speed is of considerable importance in electrical engineering. Coils are frequently used in power electronics (as passive magnetic components) and electrical machines (transformers, alternators, asynchronous machines and DC machines) require the use of magnetic materials.

To study a coil, we need to put into equation all the phenomena that occur within it. However, in the case of a coil with an iron core, the voltage at its terminals and the current flowing through it cannot simultaneously be sinusoidal, due to the presence of magnetic materials.

It is therefore not possible to apply conventional resolution methods directly, so two methods are considered for analyzing coil behavior.

• The first method consists in linearizing the problem by replacing the real coil with an equivalent coil where all quantities are sinusoidal; the usual calculation tools can then be used.

• The second method involves taking non-linear phenomena into account, and the resulting equations are then processed by computer. Here we present the method for solving the equations and some models for describing the non-linear phenomena that govern the operation of the iron-core coil.