ANALYSIS OF FACTORS INFLUENCING THE EFFICIENCY IMPROVEMENT POTENTIAL OF A WINDING CHANGEOVER IN AN ELECTRIC MACHINE

The winding configuration of an electric machine has a decisive influence on the properties of a traction drive. When designing the electric drive, the optimum compromise must be found between maximum torque, maximum power and high efficiency over a wide operating range. A decisive factor in this design conflict is the choice of the winding configuration. The concept of winding switching offers a way of solving the design conflict and improving the characteristics of the drive through the additional degree of freedom of the variable winding configuration. Switching the number of parallel winding branches in a serial and parallel configuration is a promising approach to overcome the challenge of a high spread between maximum power and high efficiency in customer related driving scenarios of an electric vehicle. The aim of this study is to identify factors influencing the efficiency improvement potential of the winding switching topology under consideration compared to a reference drive without winding switching. For this purpose, a sensitivity analysis of various parameters of the electric drive consisting of the inverter and the electric machine is carried out with regard to increasing efficiency in customer related driving scenarios. The effects of winding switching are described in relation to the influencing factors of rotor design, active length of the electric machine, star/delta winding connection and the inverter design. The conditions of an electric drive under which a winding changeover offers efficiency advantages in the customer related driving range are to be derived from the findings on the influencing factors and the effects of a winding changeover.