en Electrical Machines Design-1 Electrical Machines Design Research Paper Research Paper <p>In this paper a multiobjective optimal design method of interior permanent magnet synchronous motor ( IPMSM) for traction applications so as to maximize average torque and to minimize torque ripple has been presented. Based on train motion equations and physical properties of train, desired specifications such as steady state speed, rated output power, acceleration time and rated speed of traction motor are related to each other. By considering the same output power, steady state speed, rated voltage, rated current and different acceleration time for a specified train, multiobjective optimal design has been performed by Broyden&ndash;Fletcher&ndash;Goldfarb&ndash;Shanno (BFGS) method and finite element method (FEM) has been chosen as an analysis tool. BFGS method is one of Quasi Newton methods and is counted in classic approaches. Classic optimization methods are appropriate when FEM is applied as an analysis tool and objective function isn&rsquo;t expressed in closed form in terms of optimization variables.</p> <p style="text-align: left;"><img alt="AWT IMAGE" src="./files/site1/images/4.png" style="width: 250px; height: 250px;" ></p> Broyden-Fletcher-Goldfarb-Shanno (BFGS) Method,Interior Permanent Magnet Synchronous Motor (IPMSM),Multi-Objective Optimal Design,Quasi Newton Methods, 217 221 http://ijeee.iust.ac.ir/browse.php?a_code=A-10-377-4&slc_lang=en&sid=1 S. Ahmadi ahmadi2062@yahoo.com 180031947532846003764 180031947532846003764 Yes Iran University of Science and Technology A. Vahedi avahedi@iust.ac.ir 180031947532846003765 180031947532846003765 No Iran University of Science and Technology