IEEE TRANSACTIONS ONINDUSTRY APPLICATIONS, VOL. 55, NO. 5, SEPTEMBER/OCTOBER 2019 4613 Modeling and Experimental Verification of High-Frequency Inductive Brushless Exciter for Electrically Excited Synchronous Machines Junfei Tang , Student Member, IEEE, Yujing Liu , Senior Member, IEEE, and Nimananda Sharma , Student Member, IEEE Abstract—Electrically excited synchronous machines have shown potential to be an alternative to permanent magnet syn- chronous machines in electromobility and wind power applications. High-frequency wireless power transferring technology enables a compact design of brushless exciters for the machine. In this paper, a dynamic model of high-frequency brushless exciters is proposed for the purposes of operating condition monitoring and excitation control. The modeling is done by using arithmetic and differen- tial equations as well as considering different operation modes of the system. The operation modes are defined based on the physi- cal behaviors of the excitation circuit. Experiments are performed to verify the model with variations of different circuit parameters. Furthermore, parameter sensitivity study, component parameter selection, and loss analysis are conducted to demonstrate the ef- fectiveness of the model. The model is therefore proposed as an effective tool to assist the design and optimization of the brushless excitation system. Index Terms—Brushless exciter, electrically excited syn- chronous machine (EESM), electrical machines, modeling, power electronics. NOMENCLATURE U dc DC source voltage. i dc DC source current. u inv.dc DC-link voltage. i inv.dc DC-link current. s TA+ Switching signal of inverter switch TA+. s TA- Switching signal of inverter switch TA–. s TB+ Switching signal of inverter switch TB+. s TB- Switching signal of inverter switch TB–. u A+ Drain–source voltage across inverter switch TA+. u A- Drain–source voltage across inverter switch TA–. u B+ Drain–source voltage across inverter switch TB+. Manuscript received February 14, 2019; revised April 19, 2019; accepted May 31, 2019. Date of publication June 4, 2019; date of current version Au- gust 14, 2019. Paper 2019-EMC-0226.R1, presented at the 2018 IEEE Applied Power Electronics Conference and Exposition, San Antonio, TX, USA, Mar. 4–8, and approved for publication in the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS by the Electric Machines Committee of the IEEE Industry Ap- plications Society. This work was supported by Energimyndigheten, Sweden. (Corresponding author: Junfei Tang.) The authors are with the Chalmers University of Technology, Gothen- burg 412 96 Sweden (e-mail: junfei.tang@chalmers.se; yujing.liu@chalmers.se; sharman@chalmers.se). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIA.2019.2921259 u B- Drain–source voltage across inverter switch TB–. i A+ Current through inverter bridge A+. i A- Current through inverter bridge A–. i B+ Current through inverter bridge B+. i B- Current through inverter bridge B–. u 1 Transformer primary-side voltage. i 1 Transformer primary-side current. u 2 Transformer secondary-side voltage. i 2 Transformer secondary-side current. u ′ 1 Ideal transformer primary-side voltage. u ′ 2 Ideal transformer secondary-side voltage. u DA+ Voltage drop across rectifier diode A+. u DA- Voltage drop across rectifier diode A–. u DB+ Voltage drop across rectifier diode B+. u DB- Voltage drop across rectifier diode B–. i DA+ Current through rectifier diode A+. i DA- Current through rectifier diode A–. i DB+ Current through rectifier diode B+. i DB- Current through rectifier diode B–. u f Field winding voltage. i C f Rectifier capacitor current. i f Field winding current. R dc DC-link resistance. C dc DC-link capacitance. R ds Drain–source conduction resistance. C ds Drain–source capacitance. V F.inv Forward voltage drop across the inverter anti-parallel diodes. R 1 Transformer primary-side resistance. R 2 Transformer secondary-side resistance. L 11 Transformer primary-side self-inductance. M Transformer mutual inductance. L 22 Transformer secondary-side self-inductance. k Coupling factor. V F0 Diode threshold voltage. R d Diode conduction resistance. C f Rectifier output capacitance. R f Field winding resistance. L f Field winding inductance. T f Field winding temperature. α Cu Temperature coefficient of copper resistivity. η tot Total efficiency of the system. 0093-9994 © 2019 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.