Shielding Analysis of High-Frequency Coaxial Transformers Used for Electric Vehicle On-Board Charging Systems

Abstract

This paper introduces a High Frequency Coaxial Transformer (HFCT) with a power efficiency of >99.5% and an operational frequency between 100-300 kHz. The power rating of the HFCT can be easily scaled from 2.5 to 20 kW by adapting its simple symmetrical structure. The introduced HFCT is suitable for use with converters in Electric Vehicle (EV) on-board charging systems. It easily fulfills the design requirements of being lightweight , compact, and having a high power density and achieved a volume reduction of 75% in comparison with commercial products. Furthermore, the electromagnetic interferences are increasing with the increased operating frequency, and an inserted copper Faraday shield is used to deal with this issue (an 80.6% reduction of intra-winding capacitance was achieved). A shielding analysis, with a focus on the insertion losses, is undertaken by utilizing Finite Element Method (FEM) based numerical techniques.

Comprehensive Conceptualization, Design, and Experimental Verification of a Weight-Optimized All-SiC 2 kV/700 V DAB for an Airborne Wind Turbine

“…The maximum switching frequency is obtained from (19) and (20), by eliminating I μ,peak , for Q ZVS = Q ZVS,min , f s ≤ 6 P T,loss,max π(4 π − 3 √ 3)…”

“…According to (19) and (20) the peak value of the magnetizing current is bounded to 2 πf s Q ZVS,min < I μ,peak < 24π 4π − 3 √ 3 P T,loss,max R ds,on (23) 55 mA < I μ,peak < 94 mA, which requires a transformer primary inductance of In order to adjust the primary inductance independent of the number of primary turns and yield a great number of degrees of freedom, stacked E-core transformer designs with an air gap in the magnetic path are considered. The winding topology is chosen, such that a small parasitic primary winding capacitance results [41].…”

Investigating the Shielding Effect of Pulse Transformer Operation in Isolated Gate Drivers for SiC MOSFETs

“…These circulating pulsating currents are the main originators of electromagnetic interference (EMI) issues [16]. Various studies have been conducted to mitigate the CM noise occurrence in planar transformers, such as adding anti-phase windings [17], including a Y capacitor [18], or the insertion of faraday shielding layers [19][20][21][22]. Referring to Cochrane et al [23], the employment of a compensation capacitor with an antiphase winding to cancel noise current from flowing through MOSFET parasitic capacitor cannot considerably stop the noise current from flowing to the secondary side and return via a ground path.…”

The Faraday Shields Loss of Transformers

“…So, the capacitive coupling between the primary and secondary is significantly reduced. The Faraday shield is widely used in sensitive electronics such as audio circuits, electric vehicles [3,4], PV systems [5], and high-frequency transformers in converters [6][7][8][9][10].…”