In order to design a power transformer it is important to understand its internal electromagnetic behaviour. That can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One benefit with simulations is that the transformer can be studied before it is built physically and that the consequences of changing dimensions and parameters easily can be assessed. In this thesis a time-domain transformer model is presented. The model includes core phenomena as magnetic static hysteresis, eddy current and excess losses. Moreover, the model comprises winding phenomena as eddy currents, capacitive effects and leakage flux. The core and windings are first modelled separately and then connected together in a composite transformer model. This results in a detailed transformer model. One important result of the thesis is the feasibility to simulate dynamic magnetization including the inhomogeneous field distribution due to eddy currents in the magnetic core material. This is achieved by using a Cauer circuit combined with models for static and dynamic magnetization. Thereby, all magnetic loss components in the material can be simulated accurately. This composite dynamic magnetization model is verified through experiments showing very good correspondence with measurements. Furthermore, the composite transformer model is verified through measurements. The model is shown to yield good correspondence with measurements in normal operation and non-normal operations like no-load, inrush current and DC-magnetization. / QC20100708

<p>In the process of designing an electric power supply system for an aircraft, parameters like low weight and low losses are important. Reliability, robustness and low cost are other important factors. In the Saab Gripen aircraft, the design of the primary power supply of the electric flight control system was updated by exchanging a switching transistor regulator to a magnetic amplifier (magamp). By introducing a magamp design, weight was saved and a more reliable power supply system at a lower cost was achieved.</p><p> In this particular case, with the power supply of the electric flight control system in the Saab Gripen fighter, advantage could be taken of a specific permanent magnet generator (PM-generator). The frequency of the generator offered the perfect conditions for a magamp controller. A key parameter in designing magnetic amplifiers (magamps) is low losses. New amorphous alloys offer new possibilities of the technique in designing magnetic amplifiers, because of their extremely low losses.</p><p> The core losses are evaluated by studying the equations and diagrams specifying the power losses. The core losses are evaluated and compared with the copper losses in the process of optimizing low weight and low losses. For this an engineering tool is developed and demonstrated.</p><p> Evaluations of the hysteresis characteristics for the magnetic alloys, as well as modeling and simulation of the core losses, are presented in this work. The modeling of the core losses includes hysteresis losses, eddy current losses and excess losses as well as copper losses. The losses are studied dynamically during realistic operational conditions. The model can be used for any generic analysis of hysteresis in magnetic circuits. Applications of magnetic amplifiers in aircrafts have been demonstrated to be a feasible alternative</p>

In the process of designing an electric power supply system for an aircraft, parameters like low weight and low losses are important. Reliability, robustness and low cost are other important factors. In the Saab Gripen aircraft, the design of the primary power supply of the electric flight control system was updated by exchanging a switching transistor regulator to a magnetic amplifier (magamp). By introducing a magamp design, weight was saved and a more reliable power supply system at a lower cost was achieved. In this particular case, with the power supply of the electric flight control system in the Saab Gripen fighter, advantage could be taken of a specific permanent magnet generator (PM-generator). The frequency of the generator offered the perfect conditions for a magamp controller. A key parameter in designing magnetic amplifiers (magamps) is low losses. New amorphous alloys offer new possibilities of the technique in designing magnetic amplifiers, because of their extremely low losses. The core losses are evaluated by studying the equations and diagrams specifying the power losses. The core losses are evaluated and compared with the copper losses in the process of optimizing low weight and low losses. For this an engineering tool is developed and demonstrated. Evaluations of the hysteresis characteristics for the magnetic alloys, as well as modeling and simulation of the core losses, are presented in this work. The modeling of the core losses includes hysteresis losses, eddy current losses and excess losses as well as copper losses. The losses are studied dynamically during realistic operational conditions. The model can be used for any generic analysis of hysteresis in magnetic circuits. Applications of magnetic amplifiers in aircrafts have been demonstrated to be a feasible alternative / QC 20101103