High-frequency transformers- windings

This file is a continuation of the . Both are aimed primarily at n-winding transformers transmitting from 1 W to 10 kW and operating between 10 kHz and 10 MHz. The presents equivalent circuits with localized constants, usable by electronic simulation software, which translate the electrical behavior of these components. In the present dossier , methods for identifying all the components in these circuits are described. They are based exclusively on impedance measurements, requiring no dismantling of the component.

Transformers are used in a wide range of electrical and electronic applications. These passive components enable energy-efficient adaptation of voltage and current levels to the needs of the application, and what's more, they provide galvanic isolation between their input and output. These two properties, combined with the fact that they can temporarily store energy, make them key components in power electronics. In the , we have learned to describe the electrical behavior of these components, under all conditions encountered in electronics, by means of equivalent circuits with localized constants. Although these circuits mainly concern transformers used in power electronics converters, the generality of the approaches adopted is such that they have already been successfully applied to fields far removed from that of converters, such as the response of a 1 MVA transformer to lightning waves, or the frequency response of a hard disk sub-millimeter read head.

The resulting representation is not a complete model of the component. It doesn't show how it radiates, what temperature the windings reach, or how the current is distributed between the strands of a Litz wire. On the other hand, it does provide an accurate, synthetic representation of the component's electrical behavior within a circuit, which is useful in many circumstances. It has the particular advantage of being compatible with all electronic simulation software such as PSpice, Simplorer, Portunus,..., (cf. ). With it, we can study the temporal behavior of the component in any electronic assembly.

In this dossier, we show how to identify the elements of these equivalent circuits, based on impedance measurements taken without dismantling the component. All the practical aspects of this identification are covered: which parameters to measure, which measuring equipment to choose, how to ensure the quality of the measurements, and what accuracy to expect in the best case scenario. All these questions are addressed. To illustrate the approach, two transformers are identified. A two-winding transformer, with impedances that are easy to measure, illustrates the identification of the magnetic...