Doctoral Defense - Bhuvan Khoshoo

About the Event

The Department of Electrical and Computer Engineering 

Michigan State University 

Ph.D. Dissertation Defense 

Thursday, May 29, 2025, at 12:00 pm 

Electrical and Computer Engineering Conference Room EB 2219 

Join Zoom:  

https://msu.zoom.us/j/7900517993?omn=91371016879

Passcode: Please contact Bhuvan for passcode 

IMPROVED NUMERICAL MODELING AND EXPERIMENTAL EVALUATION OF SEGMENTED AC ELECTRIC MACHINES

BY: BHUVAN KHOSHOO

ADVISOR: DR. SHANELLE FOSTER

The increased electrification of everything demands novel and unique solutions to increase the torque density and decrease the production cost of AC electric machines. The use of segmented laminations for the construction of electric machines is an effective strategy to achieve these objectives. Segmentation also allows efficient use of multiple materials, such as oriented steel and high-strength materials, to decrease core loss and improve the structural integrity of electric machines. However, segmented designs introduce additional cut edges and parasitic gaps between segments, which negatively impact the machine's performance. Although the effects of parasitic gaps in stator segmentation have been explored, to better exploit the benefits associated with segmentation, an improved understanding of the impact of rotor segmentation alone and in combination with stator segmentation is needed. 

Numerical modeling of electric machines provides a basis for design and performance improvements. The electromagnetic performance of AC electric machines can be optimized through the strategic use of oriented steel; however, this requires accurate modeling of the properties of the oriented steel material. It is well-known that the oriented steel properties change non-linearly between the rolling and transverse directions of the lamination. The available numerical models, including commercial finite element analysis software, use coarse approximations to capture the behavior of oriented steel, which can lead to inaccurate estimation of the machine's performance. A simple but accurate modeling strategy is required. 

An assembled segmented machine includes a higher number of cut edges compared to the conventional machine. It is well-known that cutting laminations leads to deterioration of material properties close to the cut edge. These local material properties vary significantly with variations in the lamination cutting tool, tool clearance, and tool velocity. Moreover, the process used to assemble the segmented electric machine increases residual stress, which affects the local material properties. As a result, numerical modeling of segmented electric machines to accurately estimate efficiency is a challenging task. Experiments remain the simplest, yet most accurate, method for measuring the core loss of segmented electric machines. However, the literature lacks an experimental technique to separate the core loss and quantify the negative contribution of the additional cut edges. 

This research presents a comprehensive approach to address the aforementioned gaps. To close the gap in understanding the effects of rotor segmentation alone as well as its combination with stator segmentation, two theories are developed along with a novel physics-based static model. A more accurate piecewise isotropic model of magnetic properties considering the direction of magnetic flux is developed for finite element analysis modeling and validated experimentally for segmented stators manufactured using oriented steel. A novel experimental technique is presented to separate the core losses of individual tooth and back-iron regions and the additional cut edges present in manufactured segmented stators. The technique is also used to investigate the benefits observed with the use of oriented steel in segmented stators through experimental measurements. 

Persons with disabilities have the right to request and receive reasonable accommodation. Please call the Department of Electrical and Computer Engineering at 355-5066 at least one day prior to the seminar; requests received after this date will be met when possible.