Inverter Design Considerations for Variable-Pole Induction Machines in Electric Vehicles

• Published in: IEEE transactions on power electronics 2022-11, Vol.37 (11), p.13554-13565
• Main Authors: Libbos, Elie, Krause, Elisa, Banerjee, Arijit, Krein, Philip T.
• Format: Article
• Language: English
• Subjects: Converters; Electric vehicles; Electric vehicles (EVs); Inductance; induction machines (IMs); Induction motors; Inverters; Legged locomotion; Modulation; multiphase drives; pole changing; power inverters; Rotors; Torque; traction; Voltage
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2022.3177082

This article proposes a generalized inverter design framework for a variable-pole induction machine (IM). It quantifies the advantages of pole changing and a high number of inverter legs on converter efficiency and size. The framework is used to design an 18-leg drive that reconfigures a six-pole IM to four- and two-pole while increasing torque capability at maximum speed by a factor of 2.2 compared to a conventional 3-leg fixed-pole design. The framework also shows that a three-leg drive must be oversized by a factor of 1.5 to reach the same torque capability using an identical-sized machine. The proposed 18-leg drive has 50% less losses and requires 62% less dc-link capacitance compared to a 3-leg converter. The framework is used to propose a loss minimization method for the combined machine and converter, with pole count as an operational degree of freedom at partial load and high speed. As a result, variable-pole operation reduces combined machine and drive losses by up to 45% compared to a conventional three-leg drive with the same IM. An 18-leg experimental GaN-based 890 VA inverter driving a toroidally wound IM was designed, built, tested, and compared to a 3-leg inverter to validate the proposed framework.