1 DEVELOPMENT OF A TRACTION ASSISTANT PROTOTYPE BASED ON A SPHERICAL INDUCTION MOTOR Jerónimo Monteiro Barreira Duarte Under supervision of Prof. Paulo José da Costa Branco and Prof. João Filipe Pereira Fernandes Department of Electrical and Computer Engineering, IST, Lisbon, Portugal January 2018 Abstract The aim of this work was to develop a prototype based on an improved version of windings for a spherical induction motor, along with developing its thermal and mechanical project. The improved version of a planar winding configuration was adapted to a spherical configuration to fit into a wooden prototype that was created to test the electromagnetic system and determine its equivalent circuit components. The prototype was successfully built and the new windings shown to generate 133% more torque than the previous version. A CAD model was designed and computational simulations were performed to simulate its mechanical and thermal behavior under nominal conditions. The mechanical simulations shown that the model was sturdy enough to sustain a 1400 N compression load at ease, resulting in a maximum strain of 88 MPa, which is far below the yield strength of the 2014-T6 Aluminum alloy that has been chosen for the project material. The thermal simulations predict a 50 ºC reduction of the maximum temperature reached by the motor at the same nominal conditions that were considered for all tests performed with the wooden prototype. Key-words: Induction machine; spherical rotor; fins; convection; equivalent circuit. NOMENCLATURE   Radial magnetic flux density [T]  Biot number  Efficiency   Total force [N]    Total force for the double-layer [N]  Grid frequency [Hz]  Heat transfer coefficient [W/m 2 ·k]   Magnetization current [A]   Rotor current [A]   Stator current [A]   Current density [A/m 2 ]  Conductivity coefficient [W/m·k]   Characteristic length  Rotor speed [rpm]  Active power [W]   Mechanical power [W]  Reactive power [var]   Rotor resistance [Ω]   Stator resistance [Ω]   Transverse resistance [Ω]  Apparent power [VA]  Slip   Electromagnetic torque [Nm]   Stator voltage [V]   Magnetization reluctance [Ω]   Transverse reluctance [Ω]   Longitudinal impedance   Transverse impedance 1. I NTRODUCTION The study of spherical electrical drives has been taking place for the past couples of years with great expectations and fascination. However, its introduction into the industry and society has been consistently postponed due to some obstacles that are inherently linked to its practical application, along with the fact that cylindrical engines had reached its plateau of efficiency. The study of spherical rotor drives has been taking place recently while there has been allocated efforts on finding solutions that provide a wider scope to solve some current problems existing with biomedical engineering [1]-[2], robotics [3] and industry [4]-[10]. Due to the advances on new materials development and computational methods, it has been possible to conceive experimental models that promise significant improvements in terms of agility, precision and cost-quality relation