Welcome back to the course on Magnetics for Power Electronic Converters. So far, we've ignored losses in magnetic components. In reality, magnetic components have losses. In fact, magnetic components are one of the two largest contributors to losses in power converters. The other being switches. And as the switching frequency of power converters is increased, the losses in the magnetics also increase. Therefore it is important to understand the origin of the losses in magnetic components and how to minimize them. In this and the next few lessons, we will learn exactly that. Magnetic components comprise of two things, a core and a winding. And each of these contribute to losses. Winding losses are sometimes also called copper losses because windings are typically made of copper. However, you can make windings from other material as well such as aluminum. Therefore in this course, we will refer to the losses in the winding simply as winding losses. The equivalent circuit models we've developed for magnetic devices so far both inductors and transformers, have not included any losses. For example, the model for the transformer that's shown here, which we developed earlier, does model the energy stored in the transformer. So it is more than an ideal transformer model. But it does not model any losses. You can try and incorporate losses in this model by incorporating some resistors in this model for example, we could try and model the winding losses by including a resistor in series with the leakage inductance. So for example, we could simply add a resistor here to model the winding loss of the first winding, and similarly add a resistor here to model the winding loss of the second winding, and to model the core losses, what is often done is to add a resistor in parallel with the magnetizing inductance. So we could potentially include a resistor here. That models the core losses. Unfortunately, if we try and model the losses in a transformer using a model like this, in which we have used linear resistors to model the losses, it will not be very good. It'll be extremely crude and at best will capture the actual losses at one operating point of this transformer. Therefore in this course, we will not attempt to develop equivalent circuit models for magnetic devices that also capture losses. Instead, we will develop separate analytical models for both winding losses and core losses that we can use to determine the losses in our magnetic devices. Both of these losses are fairly complex, especially at high frequencies, but it turns out that core losses are relatively easier to compute. So we will begin with looking at core losses in our next lesson.