Rapid Magnetic, Thermal, and Structural Scaling of Synchronous Machines Based on Flux and Loss Maps

Abstract

In this article, we introduce a rapid and accurate method for scaling permanent magnet synchronous machines using flux linkage and loss maps. The method enables the design and comprehensive characterization of scaled machines to meet new specifications for peak torque, power, maximum operating speed, voltage, and current requirements without the need for finite-element simulations. The efficiency map of the scaled machine can be computed with negligible computational effort. The analysis encompasses the scaling of the liquid cooling jacket setup and evaluates the continuous stall torque of the final machine. Furthermore, the method addresses scaling rules for demagnetization current limits, peak short-circuit currents and uncontrolled generator voltages, allowing the evaluation of the safest shut-down strategy against the different fault scenarios. The use of the stack length versus number of turns selection plane facilitates the visualization of the key performance figures and the minimization of the stack length while adhering to inverter voltage and current constraints. Overall, this scaling method offers a streamlined approach to the preliminary design of e-motors and facilitates system-level optimization studies. The method is showcased by scaling the e-motor of the BMW i3 to meet the specifications of the moto-generator 2 of the 4th generation Toyota Prius.