Due to the limitation of working situation, the driving motor for all-electric aircraft (AEA) has a higher requirement on the weight and cooling performance of motor, so the thermal problem of driving motor is more prominent. Therefore, a high-performance cooling system based on heat pipe technology is proposed. The cooling system takes full advantage of the high thermal conductivity of the heat pipe. One end of the heat pipe is inserted into the stator yoke, and the other end is outside the motor, which is connected to an aluminum radiator. First, an experimental test is built to test the cooling performance of the proposed cooling system. Second, based on 3-D transient temperature field simulation, the influences for the axial size of the radiator and thermal conductivity of heat pipe on motor temperature rise are analyzed, which is a great significance to solve the overheating problem for driving motor. Finally, a 22-pole and 24-slot outer rotor surface-mounted permanent magnet synchronous motor (SPMSM) for AEA is designed and manufactured. Temperature rise distribution of prototype under different flight conditions is tested, and the effectiveness of the proposed cooling system is verified. The power density of the driving motor is further improved.

Aiming to address the rotor eccentricity problem caused by various factors, such as manufacturing, operation and the mass imbalance of the induction motor, the variation law of electromagnetic force wave and vibration response under rotor eccentricity during no-load operation is investigated. To begin with, on the basis of the air-gap permeability, the air-gap magnetic density components under static and dynamic eccentricity are analyzed by using the analytical method. The order and amplitude expressions of the radial electromagnetic force generated by the interaction of harmonics are obtained. Subsequently, a finite element model of the electromagnetic field was developed, and the space-time spectrum of the electromagnetic force was obtained by combining the 2D Fourier analysis. Finally, the electromagnetic force wave is used as a load to investigate the electromagnetic vibration response under different rotor eccentric forms. The effect of rotor eccentricity on the vibration response of the motor is quantitatively analyzed by using the spectral analysis method. The method of analyzing electromagnetic force wave and vibration response can also provide a reference for the same type of motor.

Most of the current fault diagnosis based on vibration analysis method has fixed feature vectors and is prone to diagnostic errors. To identify the transformer structural faults more effectively, a mechanical structure fault diagnosis method for power transformers based on integrated feature extraction and SABO-PNN is proposed. Firstly, double feature extraction is performed on the original vibration signals based on wavelet packet transform and optimized variational modal decomposition based on the Subtraction-Average-Based Optimizer (SABO). Then, weight coefficients are assigned to the vibration feature vectors based on the fuzzy analytical hierarchy process, and the combined eigenvalues are calculated from the feature vectors and fuzzy weights. The integrated eigenvalues are used as input vectors to improve the probabilistic neural network using the SABO algorithm and train the vibration signals for diagnosis. Based on digital twin technology, a vibration signal monitoring platform is constructed, which can display vibration signals and diagnostic analysis results in real time. Based on the experimental prototype of 400 kVA transformer, the vibration signals from multiple measurement points of the tank under different fault conditions were collected and diagnostic analyses were performed. The test results show that the method can accurately diagnose the mechanical structure faults of the transformer.

In order to overcome the shortcomings of traditional electric excitation claw machine such as large leakage of magnetic field and easy saturation of ferromagnetic materials, a new topology structure with permanent magnet and electrical excited of shunt excitation scheme is proposed for claw-pole machine. Firstly, the output characteristics of voltage and current in power generation and electric state for claw-pole machine are analyzed by 3-D finite element method (FEM). And the influence of different excitation currents on the saturation state of magnetic circuit is calculated. On this basis, the influence of saturation of magnetic circuit is considered for electromagnetic torque and torque ripple. Therefore, under the condition of unsaturated flux density, in order to ensure the fastest and most stable start of the vehicle, it is necessary to obtain the maximum excitation current. Finally, a hybrid-excited claw-pole machine with rated power of 1.5kW is manufactured, and the on-load and no-load characteristics of prototype are tested to verify the feasibility of the hybrid-excited topology proposed.

To effectively optimise pole shape for surface‐mounted permanent magnet synchronous machine (SPMSM), an analytical model of SPMSM with the chamfered pole is proposed for no‐load and on‐load magnetic field calculation. In this model, the pole of SPMSM is approximately segmented into pieces with regular shape and uniform magnet property, and magnetic field parameters can be obtained by subdomain superposition. Meanwhile, iron core saturation is considered to get a correction coefficient to revise air‐gap flux density, inducing flux linkage, line no‐load back electromotive force (EMF) and electromagnetic torque. Based on this analytical model, the geometry optimisation of PM can be optimised by end thickness of pole, pole‐arc coefficient of cutting and remanence, and the waveform total harmonic distortion of air‐gap flux density and no‐load back EMF are greatly reduced. To verify the analytical model, an outer rotor type SPMSM with 20‐poles and 72‐slots for tractor application is designed and manufactured. Finally, the effectiveness of the improved method is validated by the finite‐element method and experimental test.

The heating and cooling is very complex process for winding in large power transformer, which involves fluid dynamic, manufacture technology and numerical heat transfer and other related disciplines. Recently, the electromagnetic-Fluid-thermal coupled method and thermal network method are widely used by domestic and foreign researchers, whereas the oil flow distribution can not be taken into account using the two mentioned methods, thus the accuracy of the heat transfer properties will be affected. This paper presents a three-dimensional (3D) electromagnetic-fluid-thermal coupling approach to compute the hot-spot temperature-rise of winding area for large power transformer. An ODFS-400 MVA / 500 kV single-phase auto-transformer is used as the prototype model being studied and the 3D fine computation model of the winding area is established. To validate the correctness and applicability of the proposed method, the numerical results obtained from the proposed method are compared with those of experimental ones.