Analysis of AC effects, such as skin and proximity effect as well as the circulating currents and corresponding losses are usually done by finite element analysis (FEA), while mostly only a single slot is considered, neglecting the influence of neighboring phases on the flux density of the stator iron and thus the resulting slot leakage flux. As the simulation of single stranded FE models is computationally very demanding and time consuming, this work compares different levels of detail of 2D FE models and investi-gates the impact of the modelling depth on the resulting copper loss to find a computation time optimized modeling setup. Moreover, the potential increase of AC-losses is assessed for two machines that are identical except for the stator winding, so that one and the same machine is investigated at two different voltage levels, namely 400 V and 800 V. The reference machine is a 160 kW nominal power and 9000 rpm maximum speed perma-nent magnet synchronous machine. Since the magnetic circuit has to remain constant, both designs share the same overall winding scheme and total number of strands within a slot but differ in the number of parallel and serial connected strands.

By measuring 13 grades of neodymium (NdFeB), we obtained their temperature-dependent magnetic properties from 25 °C to 120 °C. Furthermore, a piecewise linear hysteresis model for NdFeB magnet is generalized to a temperature-dependent one, where temperature coefficients are introduced to consider deterioration of magnetic performance due to rising temperature. The movement of working point on hysteresis loops when temperature changes is discussed. The model is validated by massive experimental measurement of NdFeB specimens. The accuracy of the model is about 5% in the range of 25 °C-120 °C. The proposed model can be applied in electromagnetic and thermal analysis of permanent magnet motor.

This paper proposed an electromagnetic-thermal-fluidic coupling model for the accurate evaluation of electromagnetic and thermal performance of a permanent magnet synchronous machine. 2-D transient finite-element method is used to investigate electromagnetic loss including copper loss, iron loss, and magnet eddy loss. The calculated electromagnetic power loss is taken as the main source of the thermal-fluidic field and the materials property is in turn updated according to the temperature distribution. The simulation result of a rated 8 kW permanent magnetic machine is compared with the measured result, which validates the accuracy of the proposed model.

Multiphysics field coupling analysis requires that the electromagnetic and thermal performance be analyzed simultaneously. In this article, electromagnetic field and thermal field based on lumped parameter thermal network (LPTN) are coupled. This method can give a more accurate evaluation of electromagnetic and thermal performance at the design stage. Take a 7500 r/min, 4.5 kW permanent magnet (PM) rectifier generator as an example: after designing the electromagnetic model by finite element method (FEM) and the LPTN model, respectively, the electromagnetic field and thermal field are coupled by temperature-dependent material properties. Experiment shows that the error of simulated temperature and electromagnetic performance is within 5%. Moreover, this method reduces calculation time of thermal analysis dramatically, which can be applied to analyze and optimize a PM rectifier generator, as well as other typed motors.