MODELING AND ANALYSIS OF INVERTER OUTPUT TRANSFORMERS


Thesis Type: Postgraduate

Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey

Approval Date: 2010

Thesis Language: Turkish

Student: Selami BALCI

Supervisor: İBRAHİM SEFA

Abstract:

Inverter output transformers are used in Uninterruptible Power Supplies and renewable energy sources (such as solar and wind) with the aim of isolating DC link from loads and/ or adjusting DC link at the level of network voltage. Inverter transformers are different from standard transformers in terms of structural properties, such as input impedance and prevention from saturation which is caused by switching errors. Therefore design of an inverter transformer is complicated topic, which needs the information about both power electronics and design of transformer. Besides behaviors of an inverter transformers at high frequency level must be kept in view in the design. When software's are used, which enables modeling of electrical machines behaviors and analyzing with finite elements methods, some important design parameters, such as core flux distribution, induced voltages, core losses, coil inductances, stranded losses, forces in coils, can be determined with high precision. A disadvantage of conventional design methods so that does not require a large number of the production of prototypes, transformers which have different geometry and core features can be analyzed quickly. Because prediction of flux distribution is important in design process, visualization with package programs guides the designer which point will be inspected. Visualization of flux exposes escape and useful flows at different zones of magnetic circuits and at the same time it gives also information about the situation of magnetic saturation at core. In this study, modeling of classical transformers and discrete core transformers was realized and modular sinusoidal PWM via network was applied to the input of inverter transformer. Obtained results from both single core and split core transformers were compared. Therefore it was also proven that when split core transformers have been used, there was no need to use filter inductors in order to remove harmonics.