Efficient Calculation of PWM AC Losses in Hairpin Windings for Synchronous BPM Machines

This paper focuses on the alternative current (AC) losses in hairpin winding variation due to the skin and proximity effects in synchronous brushless permanent magnet machines when supplied from a pulse width modulation (PWM) inverter. Based on a motor used in a 200kW electrical drive unit, three main methodologies are investigated to demonstrate the importance of these additional losses and how it is possible to take them into account when modeling the electrical machine performance. A more rigorous approach and two more time-efficient ones are utilized for the purpose, showing powerful ways of taking into consideration the pulse width modulation induced eddy currents losses in stator conductors since the early stages of the design process. A reduction ratio of 30:1 in computation time gives the proposed methodologies great merit not only in modeling single operating points, but over the full torque-speed characteristic, efficiency maps, and drive/duty-cycles analyses.