Double Rotor Capacitor-Resonated Electromagnetic Torque Converter

This paper investigates the operation of a Magnetic-Field-Modulated Brushless Double-Rotor Machine (MFM-BDRM) as a torque converter. The coupling between the two shafts can be controlled by excitation of the outer electromagnetic field produced by the stator winding. In this paper, the outer stator winding is coupled to a capacitor bank and designed to resonate at a specific electrical frequency. The characteristics of this configuration enables passive coupling of the two shafts achieving torque conversion between the two shafts. The paper presents the mathematical modelling of the operation and presents simulation results of the electromagnetic torque converter over a wide speed range encompassing the region of the resonant frequency. Experimental results are presented on a prototype MFM-BDRM for three cases for capacitor values of 12 μF, 36 μF and 216 μF respectively. Torque transmission between two shafts is demonstrated at three representative operating points close to the respective resonant frequency. The measured current and torque values are found to be in good agreement to that predicted by the mathematical model. Effective coupling similar to the behaviour of a conventional torque converter is achieved.