EV Transmission efficiency estimation using Simulation X

Electric vehicle (EV) transmission efficiency is crucial for optimizing energy use and enhancing performance. It minimizes power losses during energy transfer from the motor to the wheels, directly impacting the vehicle's range and battery life. High efficiency ensures smoother acceleration and better driving dynamics, improving the overall user experience. Unlike internal combustion engine (ICE) transmissions, EV transmissions often employ simpler, single-speed systems, reducing complexity and energy loss. Efficient transmissions help reduce energy usage, lower costs, and minimize environmental impact. As a result, transmission efficiency plays a vital role in ensuring the sustainability and reliability of EV designs. This paper proposes a simulation model based methodology to estimate EV transmission efficiency based on modelica models developed on simulation X. A single speed EV model is developed which contains whole transmission layout discretized into simple components which include shafts, gears, bearing inertias and power loss components. The developed model considers load dependent losses which occur due to frictional losses because of surface contact between gear teeth, bearings, shafts and inertial losses based on operating conditions of the transmission required to accelerate or decelerate rotating components. Other losses due to oil churning, bearing drag and drag due to gears spinning in gear oil can be modelled using elements present in default library provided in simulation X. In the initial simulation runs, efficiency under operating region of torque speed curve of the electric motor are estimated by considering equidistant points and in subsequent runs overall power loss and efficiency over a duty cycle is estimated. Simulation results show good co-relation with measurements carried out at bench level on physical prototypes. The developed model is capable of modification to suit other single-speed EV transmissions with room left out for developing the same for multi-speed EV transmissions.