MODELING OF POWER TRANSFORMERs

M. Simeonov, I.Novakov

Technical University of Gabrovo, Bulgaria, Department Electronics, tel:++ 359 66 223 281,

e-mail:inovakov@tugab..bg

Magnetic components are a vital part of most power electronic equipment, and the models, which are used in a simulation, must faithfully reproduce or predict the behaviour of the circuit. Most of the other electronic components in these circuits have predetermined models, which have been derived from standardized components. Magnetic components, however, are rarely standardized and are generally designed for specific applications. In most cases the model, or at least the component values within the model, must be altered for each new circuit simulation. All of these are very useful for simulation, but must be used with some care if the correct model is to be obtained.

In some cases, the model may fail dramatically, thereby giving grossly erroneous results, as we shall see later. Most of the time, however, the errors are subtler. For example, the details of the noise and ringing due to parasitics in the transformer may not be reproduced correctly. Cross-regulation between windings with varying loads, high frequency winding losses. This problem usually arises from shortcomings in the models, which are being used and can, for the most part, be corrected.

 A magnetic core model has three major elements; permeability, hysteresis, and core loss. Unfortunately, both the permeability and the core loss are non-linear functions. The model of magnetic core in this paper will properly represent the non-linear permeability and the hysteresis. The core loss has not been modelled in PSPICE.