The skin effect and proximity effect at high frequencies would greatly increase the AC copper loss of high speed permanent magnet machines (HSPMMs), especially for form-wound windings. However, the influence of some factors on the AC loss of the form-wound winding is still unclear in the existing research. Therefore, this paper presents comprehensive research on the AC copper loss of HSPMM with form-wound windings. Firstly, the model of eddy current field considering the skin effect and the proximity effect for form-wound windings is established, and the AC losses of each stator slot and each conductor at high frequency are obtained. In addition, the factors affecting the AC loss are comprehensively analyzed through the eddy current field, including the conductor size, the number of conductors per slot, and the operating temperature. Furthermore, the influence of strand wire sizes on temperature distribution of HSPMM is also implemented by establishing a temperature calculation model. Finally, the theoretical results are verified by testing the AC resistances of five coils at different frequencies and the temperature characteristic of an HSPMM prototype with form-wound windings.

AC copper loss from stator winding is one of the main losses of the high-speed permanent magnet machines (HSPMMs) and directly affects the performance of the machines. AC copper losses are influenced by many factors, including the frequency, conductor diameter, temperature performance, etc. These factors cause the AC losses to increase significantly at high frequencies due to the skin effect and proximity effect. In this paper, a comprehensive analysis of the AC copper losses of HSPMMs with round copper wire windings is presented. Firstly, the structure and parameters of a 60 kW, 30,000 rpm high-speed permanent magnet machine are provided. Then, based on this parameter, a 2D-finite element model (2D-FEM) is established to obtain the AC copper loss. Through the eddy-current field analysis, the current density distribution of the stator winding and the variation trends of AC copper losses under different frequencies are observed. In addition, by comparing the winding current density distribution and the AC copper loss value under different conditions, the influencing factors of AC winding losses are comprehensively analyzed, including the frequency, conductor diameter, number of conductors per slot, notch height of the stator slot, and working temperature. Finally, four stator coil cases are manufactured, which have different conductor diameters and wire strands. The AC losses of the four cases at different frequencies are tested, and the theoretical results are verified by measuring the AC/DC loss ratios (k_ac) of different conductor cases at various frequencies.

Predictive current control (PCC) is an advanced control strategy for permanent magnet synchronous motors (PMSM). When the motor drive system is undisturbed, predictive current control exhibits a good dynamic response speed and steady−state performance, but the conventional PCC control performance of PMSM that depends on the motor body model is vulnerable to parameter perturbation. Aiming at this problem, an improved model−free predictive current control (IMFPCC) strategy based on a high−gain disturbance observer (HGDO) is proposed in this paper. The proposed strategy is introduced with the idea of model−free control, relying only on the system input and output to build an ultra−local current prediction model, which gets rid of the constraints of the motor body parameters. In the paper, the ultra−local structure is optimized by comparing and analyzing the equation of the state of the classical ultra−local structure and PMSM system. The system’s current state variables are incorporated into the ultra−local system modeling, as a result, the current estimation errors existing in the classical ultra−local structure are eliminated. For the unmodeled and parametric perturbation part of the ultra−local system, a high−gain disturbance observer is designed to estimate it in real time. Finally, the proposed IMFPCC strategy is compared with the conventional model−based predictive current control (MPCC) and the conventional model−free predictive current control (CMFPCC) in simulation and experiment. The results show that the current steady−state error of the IMFPCC strategy in the case of parameter variation is only 50% of the MPCC method, which proves the effectiveness and correctness of the proposed strategy.