Abstract: Permanent Magnet Synchronous Motors (PMSMs), Synchronous Reluctance Machines (SynRMs), and Permanent Magnet-assisted Synchronous Reluctance Machines (PMaSynRMs) are widely used classes of traction motors in EVs. PMSMs offer high efficiency and power density but are costly due to rare-earth magnets. SynRMs are cheaper and simpler but have lower torque density and power factor. PMaSynRMs combine both, using minimal magnets to enhance SynRM performance.

For applications demanding a very high Constant Power Speed Range (CPSR), the motor must operate extensively in the Field-Weakening (FW) region, where efficiency significantly drops. An alternative to deep FW operation is to either increase the DC bus voltage or use winding changeover techniques — both of which add to the drive’s weight and cost. In this work, a multipole motor for EVs that demands a wide CPSR, is discussed. The machine features two distinct pole sets and operates as a PMaSynRM. The rotor of the machine is a hybrid of SynRM and PMSM. The stator houses two sets of 3-phase windings, corresponding to each pole. Both components are operated till an intermediate speed, after which, the excitation of SynRM is removed without the use of any switches, since the back-EMF in SynRM due to PM is negligible. Only the PM part is operated till maximum speed, without entering FW. Hence, the proposed machine can be used to obtain extended speed with improved efficiency due to the absence of extra FW current.

As an extension of the multipole concept, a ferrite-assisted PMaSynRM is developed. The proposed machine utilizes ferrite magnets embedded within multi-barrier rotor structures to achieve improved torque capability and efficiency at a lower material cost. The concept of dual-pole formation through full and segmented magnet placement is analyzed. Multiple machine configurations, namely three-barrier and two-barrier designs, are investigated. Electromagnetic performance, back-emf characteristics, torque ripple behavior, and torque-speed capabilities are evaluated through simulation and experimental studies. The concepts of both machines, along with their operating principles and experimental results, will be discussed.

Event Details
Title: Design of Multi-Pole Permanent Magnet and Ferrite-Assisted Synchronous Reluctance Machines for Extended Speed Range Electric Vehicle Drives (PhD Viva Voce)
Date: August 25, 2026 at 02:00 PM
Venue: Google Meet (https://meet.google.com/yoy-ebro-oua)
Speaker: Ms. Veena P (EE19D208)
Guide: Dr. Kamalesh Hatua
Type: PHD seminar

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