In surface-mounted permanent magnet synchronous motors, two types of magnet tolerances: magnet misplacements and magnetisation errors, cause additional torque ripple harmonic components and lead to the dispersion of torque ripple in mass production of motors. This paper analyses the effects of the magnet tolerances on torque ripple and estimates the statistical values of the magnitudes in each harmonic of additional torque ripple resulting from Gaussian distributed magnet tolerances. By using synthesis method, the analytical expressions are derived which reveal the relationship between the magnet tolerances and the magnitudes of the additional torque ripple harmonics. Based on the analytical expressions, the statistical values of each harmonic's magnitude are predicted. The expected values and standard deviations of the harmonics' magnitudes are calculated and verified by both the simulations and experiments.

The objective of this paper is to present the design equations of the conventional double-sided axial-flux slotless brushless DC machine (BLDC) and the new one with the trapezoidal cross-section core as well as performances comparison based on the proposed design algorithm. Direct search method is used to find the optimum designs, whereas machines with the rated power of 0.25–10 kW are compared. Efficiency and size of the optimum designed machines are presented to make a comprehensive study for choosing the best topology from the viewpoint of electrical and geometrical characteristics. Finite element analysis and experimental results are presented to show the validity of the derived equations and the design outcomes.

In this paper, a new linear primary permanent magnet vernier (LPPMV) machine is developed for direct-drive wave energy conversion. Owing to the magnetic gearing effect, the LPPMV machine possesses the advantages of high thrust force and low speed motion. After describing the machine structure, the operation principle of the machine is analysed and compared using two methods, namely, the magnetic gearing principle and the straightforward magnetic path. Then the characteristics are analysed by using the finite element method. Considering the unbalance of the no-load flux linkage and the inductance among the three phases, the mathematical model of the proposed machine is established, which is significantly different to that of the traditional permanent magnet machine. Finally, the machine is prototyped and tested so as to experimentally verify the theoretical analysis.

The ageing rate of cellulose insulation materials (paper/pressboard) in oil-impregnated transformers is largely determined by moisture. In this paper, several experiments were conducted under controlled laboratory conditions to quantitatively diagnose the amount of moisture in cellulose insulation using frequency domain spectroscopy (FDS) technique, which has been proven to be an effective tool to predict the insulation condition in oil-impregnated power equipment. The frequency dielectric response in oil-impregnated pressboards, moisture content as well as test temperature, was monitored carefully, and a new dielectric characteristic parameter for the diagnosis of moisture content was proposed. In addition, the master curve technique was introduced to calibrate the temperature effect on FDS measurement results. These experiments revealed that a strong correlation exists between frequency dielectric parameter and moisture content in cellulose insulation. Such correlation can be utilised for better prediction of moisture content in paper–oil insulation. A modified assessment method for the diagnosis of moisture content in paper–oil insulation was investigated and its effectiveness was also demonstrated using a case.

Suspension electromagnets are an essential component of the low-speed maglev train. Their performance has a direct bearing on the technical and economical performance, as well as the safety, of the entire train. This report describes a new form of electromagnet, whose structure combines permanent magnets and electromagnetic coils. This report then uses a two-dimensional (2D)/3D finite element approach in order to analyse the electromagnetic characteristics of this new form of hybrid electromagnet. A simulation was conducted according to four typical operating conditions: a full load with a fixed suspension gap of 8 mm; a full load with an initial suspension gap of 18 mm; a full load with a suspension gap of 10 mm; and an empty load with a 3 mm gap as well as a guard that prevented the magnet from getting caught on the tracks. The report equally discusses the extent to which the suspension gap and the current of the electromagnetic coil affect the electromagnet's force. The calculations and experiments reveal that this new, hybrid form of electromagnet is feasible and significantly contributes to saving energy.

This paper proposes an on-board integrated battery charger for an electric-propulsion system. The system includes a rectifying diode bridge, an inverter, a permanent magnet motor, a digital signal processor, a battery set and three relays. By suitably controlling the three relays and the power switches of the inverter, the proposed system can be operated as either an electric-propulsion system or a battery charger. The integrated battery charger can be used to charge a 48 V battery set or a 192 V battery set from a single-phase 110 V _rms grid. The battery charger can be operated in a boost-converter charging mode or in buck-converter charging mode with input power factor higher than 0.9 when operating with 48 V battery or 192 V battery, which can meet the IEC 1000-3-2 standard. Only a diode bridge, an inductance-capacitance (LC) filter, and three additional relays are required in addition to the components for propulsion. The windings of the motor and the power switches of the inverter are shared for both the electric-propulsion system and the battery charger. A digital signal processor, TMS-320-F-2808, is used to execute all of the control algorithms. Experimental results validate the theoretical analysis and separately show the correctness and feasibility of the proposed method.

Aeronautical ground lighting (AGL) systems provide visual reference to aircraft during airport operations. In AGL systems, constant current regulators feed a series circuit composed of luminaires supplied through transformers. Component modelling is necessary to simulate AGL systems, and thus characterise and predict their behaviour. This paper presents an AGL transformer model including transformer core saturation. Moreover, a procedure to estimate transformer model parameters is proposed. Both the model and the estimation method are validated with extensive measurements on more than 20 AGL transformers of different power ratings and trade names.

A recurrent fuzzy neural cerebellar model articulation network (RFNCMAN) control is proposed in this paper for position servo drive systems to track various periodical position references with robustness. The adopted position servo drive system is designed using a six-phase PMSM and equipped with a fault-tolerant control scheme. First, an ideal computed torque controller is designed for the tracking of the rotor position reference command. Since the uncertainties of the PMSM position servo drive system are difficult to know in advance, it is impossible to design an ideal computed control law for practical applications. Therefore, the RFNCMAN is proposed to mimic the ideal computed torque controller with a compensated controller to compensate the approximation error. In the RFNCMAN, a recurrent fuzzy cerebellar model articulation network (RFCMAN) is adopted in the first dimension to enhance the online learning rate and localisation learning capability. Moreover, a general recurrent fuzzy neural network (RFNN) is adopted in the second dimension to enhance the generalisation performance and to reduce the required memory and rule numbers. Finally, the proposed position control system is implemented in a 32-bit floating-point DSP. The effectiveness of the proposed RFNCMAN control system is verified by some experimental results.

This paper presents a position servo control approach for a permanent magnet linear synchronous motor. The non-linear motor dynamics is expressed in the backstepping control scheme on which a recursive designing procedure is carried out. Based on the desired motion trajectory, the magnetic thrust force is first calculated and then treated as the control objective for the next subsystems. The command voltages to stabilise the whole system are established concerning the electric properties of the magnetic windings. To overcome the impacts of system uncertainties, an adaptive neural network is exploited to estimate the uncertainty and provide necessary compensation in the control effort. Based on the Lyapunov functional analysis, the adaptive laws for online tuning the parameters of the neural networks are derived so that the precision of position servo control can be improved. Compared with the conventional current regulated control scheme, this investigation introduces a voltage-controlled pulse-width modulation with a complete theoretic base, including the mechanical and electrical dynamics. The effectiveness of the proposed approach is verified by the experimental results and a comparison study with a recent work developed in the robust fuzzy PI control scheme.

Irreversible demagnetisation of a permanent magnet (PM) at high temperature can be caused by the field distributions because of the stator currents. It can be prevented if the magnet thickness is sufficient. However local irreversible demagnetisation can occur even if the magnet thickness is sufficient. The local irreversible demagnetisation is varied according to the magnetic path. To analyse the cause of local irreversible demagnetisation, the authors introduced an interior PMSM (IPMSM), consisting of a V-shaped magnet and concentrated winding, and performed a parameter analysis of the magnetic field based on the barrier width and magnet position considerably related to the magnetic path using the finite-element method. On the basis of the results, the authors developed a model avoiding local irreversible demagnetisation. A maximum load test was performed after a thermal saturation test to confirm whether irreversible demagnetisation of the manufactured models occurred. Finally, to verify the validity of the finite-element analysis (FEA) results, the torque, efficiency, power factor and induced voltage of the manufactured model, which were obtained by FEA, were compared with the test results.