PhD student Shivang Agrawal with Advisor A. Banerjee

A brushless doubly-fed machine (BDFM) is an attractive option for megawatt-scale turbo-electric propulsion systems due to use of a partially-rated power converter, reduced maintenance, and absence of permanent magnets. However, BDFRMs have inherently poor torque density and high torque ripple because of using a sub-optimal rotor. We have proposed an analytical model to compute the air-gap flux density and torque characteristics, with the aim of modeling the effect of the flux barriers on the mean and ripple torque. Through analytical and finite-element analysis, it has been verified that the position of the flux-barrier ends highly influences the torque waveform, and thus cannot be arbitrarily designed. The rotor geometry, along with the stator current excitations, are optimized to achieve a high torque density BDFRM. Figure 13 shows the optimized stator and rotor which has been laser-cut from M-19 C5 steel laminations and bonded using Remisol EB 548. Figure 14 shows the test setup for the experimental validation of BDFRM.
This research is supported by Grainger Center for Electric Machinery and Electromechanics.

Figure 13. Prototype BDFRM constructed in-house.

Figure 14. Testbed used for the experimental validation.