Shivang Agrawal with adviser 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 the 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 achieving a high torque density BDFRM. Figure 1 shows the optimized stator and rotor which has been laser cut from M-19 C5 steel laminations and bonded using Remisol EB 548. Figure 2 shows the test setup for the experimental validation of BDFRM. The research is supported by Grainger Center for Electric Machinery and Electromechanics.

Figure 1: Prototype BDFRM constructed in-house

Figure 2: Tested used for the experimental validation