Theoretical analysis and simulation study of resonant coupling air core power transformers

Thanks to the inherent features of small volume and light weight, high frequency power transformers are widely used as the key module for DC power supply. With the increasing prevalence of DC power technologies, high frequency power transformers are widely implemented in large scale DC conversions. However, conventional iron-core materials used in high frequency power transformers inhibit the raising of power capacity and frequency because the ideal iron core materials with excellent high frequency performance and low power loss are not readily available. In this paper, a new type of power transformer is proposed using magnetic resonance coupling and air-core techniques. Theoretical analysis is conducted based on π-shape model of iron-core high frequency and circuit theory of resonant coupling wireless power transfer. After that simulation models are built using the parameters fulfilling the mentioned voltage ratio with Pspice software package. And output power as well as transfer efficiency are calculated. We observed that the stray capacitors which are very small compare to coupling capacitor have little impact on tranfer property. Meanwhile, the stray capacitor C₀₁ and C₀₂ have stronger impact than C₁₂. To get the same voltage ratio, the Series-Series and Series-Parallel model have different parameters. Besides, the two type models have different property to load resistance and coupling coefficient.