This paper investigates the surface-mounted permanent-magnet (SPM) and the interior permanent-magnet (IPM) motors for high-speed applications. An SPM motor and an IPM motor are designed with the same power/speed rate and the same key dimensions. Finite-element analysis is used to compare the mechanical, electromagnetic, and antidemagnetization performances of the two motors, and lumped parameter thermal networks are involved to compare their thermal performances. It can be concluded from the comparisons that the IPM motor has comparable electromagnetic performances with the SPM motor in high-speed operations, and its costs and torque per PM weight are superior to those of the SPM motor. However, its rotor structure is not as robust and is prone to irreversible demagnetization.

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This paper presents the design, analysis and verification of a 150 kW, 24 krpm high speed permanent magnet motor (HSPMM). The HSPMM is a two-pole motor with Gramme ring windings, which can shorten the end winding length and improve the rotor stiffness. The design procedure based on analytical methods, including the rotor mechanical design, magnetic design and cooling design is described. Then a prototype designed by the proposed design techniques is further verified by numerical methods including finite element analysis (FEA) and computational fluid dynamics (CFD) and experiments.

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This paper investigates the electromagnetic and thermal performances of the open-circuit air cooled high-speed permanent magnet motor (HSPMM) with Gramme ring windings. Take a 36 kr/min, 75 kW HSPMM as an example, the electromagnetic losses, in particular the rotor eddy current loss and the stator iron loss of the motor are calculated. The influences of switching frequency and air gap length on these losses are studied. Then, a computational fluid dynamics (CFD) model is composed to calculate its coolant flow parameters and the temperature distribution. Based on the CFD results, a lumped-parameter thermal network (LPTN) is created and verified. Then, a 24 kr/min, 140 kW prototype with the same structure and cooling configuration is designed using the LPTN. Experiments show that the calculated results are with reasonable accuracy. Finally, a sensitivity analysis is applied to the 140 kW prototype based on the LPTN to disclose the influences of different parameters on the rotor permanent magnet temperature rise.

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This paper investigates the losses of a high-speed permanent magnet motor. The iron losses are calculated by a model that can consider the skin effect and rotational loss. The rotor eddy current losses are estimated by a fast hybrid method that can consider the end effect. Pulse-width modulation (PWM) harmonics brought by the voltage source inverter (VSI) are considered in the loss calculations. Then the temperature distribution of the motor is evaluated by using the calculated loss results and computational fluid dynamic (CFD) modeling. Finally, based on the CFD results, the motor structure is optimized to achieve better rotor cooling. The outer slots are closed to force the cooling air flow through the rotor surface. Calculated temperature distributions and optimization results are verified by measurements.

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High speed permanent magnet machines (HSPMMs) have a promising future in applications such as aeronautics and astronautics, energy and ultra-precision manufacturing. This paper enumerates various stator and rotor structures and materials of the HSPMM in literature. Then different losses in the HSPMM are summarized in aspects of stator iron loss, copper loss, rotor eddy current loss and air friction loss. Various motor temperature rise calculation methods and three kinds of high speed rotor bearings are compared, followed by an overview of the problems linked to the rotor strength and dynamics analysis. Finally, development trends of the HSPMM related technologies are summarized and prospected.

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The most accurate method to design the stator coreless axial flux permanent magnet machine is the 3D finite-element analysis, which is exceedingly time-consuming. To solve this problem, this paper presents an analytical design method. Firstly, the analytical model of the 3D no-load magnetic field distribution of the machine is proposed. Analytical expressions of the back electromotive force of the machine are derived based on the model by using the winding function method. Inductance and resistance are calculated based on parameters such as the estimated ending connection length. Machine losses are analyzed in detail and analytical equations of them are presented. Then equations for the steady state performance are derived bases on the equivalent circuit of the machine. Finally the proposed design method is applied to three prototype machines with different rate powers and winding configurations. The prototype machines were tested and the calculated results are compared with the experimental ones, showing good agreements.@en

An analytical method is presented to predict the magnetic field of the axial magnetized tubular ironless permanent magnet linear motor (TIPMLM) based on the magnetic charge method in the cylindrical coordinate system. The no-load magnetic field distribution is analyzed, the expressions of the axial and radial components of which are derived. By combining the motor parameters, the back electromotive force (EMF) and thrust force are derived. Then the no-load field distribution, back EMF and thrust force of a TIPMLM are calculated by using the proposed method and the finite element method (FEM), separately. Finally, the effect of load current on the magnetic field of the motor is analyzed by FEM. It is shown that the results of the proposed analytical method and FEM are very close to each other, which verifies the proposed analytical method. The effect of load current on the magnetic field distribution on the surface of the permanent magnets is negligible, which is one of the merits of the investigated motor structure.

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This paper presents an axial flux stator coreless permanent magnet flywheel motor/generator set for pulsed power application. This structure can adjust the back electromotive force (EMF) by rotating one of the double stators. Detailed topology of the structure is presented and a closed-form analytical design approach is described. A downsized prototype machine and the corresponding driver are designed and constructed based on the presented analytical approach. No-load parameters of the prototype are measured and compared with the predicted one, showing good agreements. Then losses of the prototype are analyzed. Finally, the prototype is driven in both brushless DC (BLDC) mode and space vector pulse width modulation (SVPWM) mode; actual charging and discharging waveforms are presented.@en

In a permanent magnet synchronous generator (PMSG) with modular winding, significant eddy current may be induced in the rotor magnets due to asynchronous rotating stator magneto-motive forces (MMFs), and a rectifier load may signify the situation further. The eddy-current loss prediction in the rotor magnets of a PMSG with modular winding feeding a rectifier load is described. An analytical method considering the stator current harmonics and stator MMF spatial harmonics and a time-stepping, coupled-circuit, 2-D finite-element method (FEM) are adopted. The predicted losses obtained from these two methods are compared and investigated.@en