International Journal of Power Electronics and Drive Systems (IJPEDS) Vol. 12, No. 3, September 2021, pp. 1369~1378 ISSN: 2088-8694, DOI: 10.11591/ijpeds.v12.i3.pp1369-1378  1369 Journal homepage: http://ijpeds.iaescore.com Online efficiency optimization of IPMSM for electric vehicles Hanaa Elsherbiny, Mohamed Kamal Ahmed, Mahmoud A. Elwany Department of Electrical Engineering, Faculty of Engineering, El-Azhar University, Cairo, Egypt Article Info ABSTRACT Article history: Received Mar 16, 2021 Revised Apr 30, 2021 Accepted May 9, 2021 This paper presents an online efficiency optimization method for the interior permanent magnet synchronous motor (IPMSM) drive system in an electric vehicle (EV). The proposed method considers accurately the total system losses including fundamental copper and iron losses, harmonic copper and iron losses, magnet loss, and inverter losses. Therefore, it has the capability to always guarantee maximum efficiency control. A highly trusted machine model is built using finite element analysis (FEA). This model considers accurately the magnetic saturation, spatial harmonics, and iron loss effect. The overall system efficiency is estimated online based on the accurate determination of system loss, and then the optimum current angle is defined online for the maximum efficiency per ampere (MEPA) control. A series of results is conducted to show the effectiveness and fidelity of proposed method. The results show the superior performance of proposed method over the conventional offline efficiency optimization methods. Keywords: Finite element analysis Interior permanent magnet synchronous motors Inverter and iron losses Online efficiency optimization This is an open access article under the CC BY-SA license. Corresponding Author: Hanaa Elsherbiny Department of Electrical Engineering El-Azhar University El-Nasr Road, Nasr City, 11751 Cairo, Egypt Email: Hanaaelsherbiny.60@azhar.edu.eg 1. INTRODUCTION The electric vehicles (EVs) are the future of transportation. They have lots of advantages such as no emissions, low maintenance, low cost, and safety drive [1]-[3]. However, the batteries have limited capacities that affects the milage per charge. As most of battery power is consumed by the main drive system (motor + converter), it is very important to optimize their efficiencies to increase milage per battery charge. At early days of transportation, the direct current machines (DCMs) were used because they have simple and linear controls. However, the existence of commutator and brushes cause lots of problems leading to lower speed ranges and lower efficiencies [4]. Recentely, due to the huge progress in field of power electronics and semi-conductors, the induction machines (IMs), synchronous reluctance machines (SynRMs), switched reluctance machines (SRMs), and interior permanent magnet synchronous machines (IPMSMs) are reported for EVs. Due to the presence of copper losses in IMs, they have relatively low efficiencies and low power factors which is disadvantageous for EV traction. The SynRMs have relatively high torque ripple. They also need high volt amper (VA) rating of inverters due to the poor power factor. The SRMs have hnherited high torque ripple due to the sequential commutation of coils, doubly salient structure, and deep magnetic saturation. They also poss complicated control algorithms [4]-[7]. The IPMSMs have the best performance to be used as the main drive in EVs. They offer not only high efficiency, wide speed range, high power density, but also small weight and size with low noise [8], [9]. Despite the high efficiency of the IPMSMs, much research has been conducted to improve motor efficiency. On one side, new design configurations for both the stator and rotor are developed to improve motor efficiency [5], [8]. Also, the converter design is investigated for better system efficiency [10], [11]. On the other side, new control