Eccentricity fault with 10% severity is probably the only existing fault in a brand new healthy electrical machine that is acceptable as a manufacturing tolerance. This fault can be developed due to a continuous pull between stator and rotor, even in a de-energized machine. So, it must be diagnosed,and its severity monitored. The authors introduced and criticized various indices for eccentricity fault diagnosis. Advantages, drawbacks, and ambiguous points of each index and potential ground for improvement of these techniques are addressed. Moreover, different eccentric PM machine modelling techniques are reviewed and environmental factors affecting the eccentricity fault detection process are discussed. This survey covers all direct current and alternating current PM machines. It provides information about the researches performed since 1986 and it is helpful to newcomers to this field, artisans, and protection system designers. Considering the given information, the readers achieve enough understanding of the weaknesses and strong points of each eccentricity fault diagnosis index. Then, these indices are evaluated through assigning weight coefficients under various scenarios. Interested individuals can modify these weight coefficients based on the specifics of the application and decide which index is the most appropriate.

The rim-driven integrated motor propulsor (IMP) has received much attention in recent years, owing to its superiority in flexibility, reliability, and space occupation. For this propulsion system, radially thin motors with high torque and large air gaps are essential. Two-segment Halbach array permanent magnets with unequal segment-arc are adopted to enable a thin rotor and a large air gap. The general analytical solution of the magnetic field is presented. Based on the analytical calculation of the Halbach motor performance, the necessity of the rotor core was discussed, and the Halbach array was optimised with an analytical method to maximise the electromagnetic torque. This study also tried and compared three designs of the integrated motor stator to further reduce the radial thickness, and the slotted stator proved more reasonable. The fabrication of an IMP prototype was completed, and the experimental data of the integrated motor are presented and compared with the calculated results. This study also conducted the water tunnel experiment of the IMP prototype to test the integrated motor performance in the overall IMP system. The measured rotational speed and output thrust are less than expected, so the friction loss in the IMP gap flow field is calculated and analysed.

Here, the outcomes of experimental measurements and finite-element simulations are used to develop MATLAB/Simulink models for evaluating the transient dynamic behaviour of the well-known dual-core presaturated core fault current limiter (PCFCL), either for single- or three-phase configurations. These models are based on calculating the total flux linkage–current characteristics of the AC coils at different levels of DC biasing current, taking into consideration the induced voltage across the DC coil terminals due to significant flux variation during the fault condition. On the other hand, the time-varying self-inductance and the self-inductance–current characteristics of the PCFCL are directly developed through Simulink modelling. It is worth mentioning that the self-inductance–current characteristic enables an important and quick design optimisation tool for PCFCL, where the dynamic inductance term significantly contributes to the total voltage drop across PCFCL in comparison to the static inductance. These total flux linkage and inductance versus current models can be directly used for modelling the dynamic transient behaviour of PCFCL when attached to any electrical transient programme used for analysing complex electrical power systems, with remarkable accuracy, quicker, and easier for various network scenarios and fault conditions.

This study presents design and performance analyses for a new line start axial flux permanent magnet synchronous motors (AF-PMSMs). The innovative part of this study is that AF-PMSM can start directly from the line and operate with high efficiency and power factor after synchronisation. Prototype manufacturing was carried out after completing the analytical and electromagnetic designs for the targeted motor. The synchronisation capacity, power capacity, power–speed characteristic, power-efficiency relationship along with the total harmonic distortion and back-emf waveform of the induced voltage have been examined for the prototype motor. Simulation studies have been verified experimentally. The results obtained were compared with an induction motor with the same power. It was observed as a result of the work carried out and a line start AF-PMSM is obtained that is 4–10% more efficient in comparison with an induction motor having the same power.

The B–H curve and iron loss of electrical steel sheets are essential data for predicting the performance of electric motors. The Epstein frame test is widely adopted to acquire these magnetic properties. However, for rotating electric machines with relatively small geometry, the ring specimen test is preferred because of its simplicity and geometric similarity. This study deals with the experimental verification of the ring specimen test. The B–H curve and iron loss of non-oriented electrical steel sheets are measured via the Epstein frame test and the ring specimen test. Each result is applied in finite element analysis (FEA) of the fabricated electric motor. Furthermore, using these FEA results and the d-q-axis equivalent circuit, the performance of the electric motor is predicted. For experimental verification, electric motor tests are performed under no-load and load conditions.

Compression of windings is known to give thermal and performance benefits. The aim here is to investigate how the health of stator winding insulation systems are influenced by on-tooth coil pressing. A set of compressed coils have been aged by exposing them to high temperatures. Winding insulation resistance (IR) was monitored during this process to experimentally validate whether compressed coils remained healthy in terms of electrical insulation. In this case, a single stress (i.e. temperature) model is used to predict the reliability of the compressed coils. Accelerated life tests have been conducted to inspect the life expectancy and thermal endurance of the compressed stator coils. The employed statistical model (Arrhenius-Weibull) demonstrates that on-tooth coil pressing reduces the life expectancy dramatically due to reduced turn to ground wall insulation dielectric strength.

In order to eliminate the coupling between of radial four degree-of-freedoms (DOFs) in a rigid rotor supported by two radial active magnetic bearings and to suppress the rotor imbalance vibration, a feedforward decoupling control was proposed, and then the rotor imbalance compensation based on imbalance identification was used after the rotor system had been decoupled. A time-optimal tracking differentiator was used to improve the performances of feedforward decoupling control and imbalance compensation. Numerical simulations and experiment results show that the radial four DOF coupling system could be completely decoupled into four single DOF systems by the feedforward decoupling controller, the imbalance vibration of the decoupled system could be effectively suppressed by the imbalance compensation, the performances of decoupling and imbalance compensation could be improved and the anti-interference ability of the control system could be enhanced by using the time-optimal tracking differentiator.

The increasing number of non-linear loads and renewable energy sources causes a decrease in the power quality in the power networks. Therefore, tests of current transformers should be performed in similar conditions. This requires generation by a high current testing transformer of distorted currents that rms values are from a few hundred to several thousands of amperes with a given harmonics levels. However, its frequency band of operation is limited by inductances of its windings and connected load that result from the length and parameters of the used current track and connected device under test. To ensure the constant rms value of higher harmonic of distorted secondary current with the increase of its frequency proportional increase of the rms value of this harmonic in distorted primary voltage of the high current testing transformer is required. However, the maximum permissible value of primary voltage is limited by the dielectric strength of insulation of the primary winding. The purpose of presented studies is to determine the factors that condition the frequency band of operation of a high current testing transformer and limits the range of higher harmonics while testing of the transformation accuracy of instrument current transformers for distorted currents.

In comparison with the traditional plug-in charging systems for the electric bike (EB), wireless power transfer (WPT) systems have superior advantages of convenience and safety. Combining the application requirement range of the EB, this study proposes a three-coil structure-based WPT system in order to achieve ideal and reliable constant current (CC) output and constant voltage (CV) output without the need for a sophisticated control strategy and the real-time communication links between the transmitter and receiver sides. Two ac switches are utilised at the transmitter side to implement the change of charging mode from CC to CV. By correctly selecting the parameters of compensation components, the required load-independent CC and CV characteristics with zero phase angle in the CC and CV modes can be achieved. Besides this, a load identification method based on the active power calculation used to estimate the equivalent resistance of the battery in the whole charging process, is utilised to judge the switching point from CC to CV mode. Finally, the feasibility of the method is verified through the construction of a laboratory platform with a 3.3 A charging current and a 57 V charging voltage.

Electric mobility has become an essential part of the future of transportation. Detection, diagnosis and prognosis of fault in electric drives are improving the reliability, of electric vehicles (EV). Permanent magnet synchronous motor (PMSM) drives are used in a large variety of applications due to their dynamic performances, higher power density and higher efficiency. In this study, health monitoring and prognosis of PMSM is developed by creating intelligent digital twin (i-DT) in MATLAB/Simulink. An artificial neural network (ANN) and fuzzy logic are used for mapping inputs distance, time of travel of EV and outputs casing temperature, winding temperature, time to refill the bearing lubricant, percentage deterioration of magnetic flux to compute remaining useful life (RUL) of permanent magnet (PM). Health monitoring and prognosis of EV motor using i-DT is developed with two approaches. Firstly, in-house health monitoring and prognosis is developed to monitor the performance of the motor in-house. Secondly, Remote Health Monitoring and Prognosis Centre (RHMPC) is developed to monitor the performance of the motor remotely using cloud communication by the service provider of the EV. The simulation results prove that the RUL of PM and time to refill the bearing lubricant obtained by i-DT twins theoretical results.

This study proposes a novel permanent magnet synchronous motor (PMSM) driven system based on isolated shoot-through Z-source inverter (IST-ZSI). The IST-ZSI is utilised to replace the traditional Z-source inverter. Compared with the conventional Z-source inverter-based PMSM drive system, the new drive system can not only solve the coupling of the boost factor and modulation but also provide a large regulation range of the output voltage. For the PMSM drive system, a variable damping injection controller is proposed via the passivity-based control and maximum torque per ampere control principle. Then, the load torque observer is designed to improve the stability of the PMSM system with uncertain load torque. The simulation and experimental results show that the variable damping injection control has satisfactory dynamic and static control performance.

This study presents an investigation on iron loss and start-up ability of a 1.5 kW output power with rated speed 5850 r/min 6/2 switched reluctance machine (SRM), which is used as a prime motor to directly drive centrifugal blower. Two winding connection types of the SRM are investigated, including the symmetrical magnetic topology (SyMT) and asymmetrical magnetic topology (ASyMT). The two types are proposed to settle poor self-start ability of the 6/2 SRM and high iron loss density of high-speed SRM. According to the simulation results, the SyMT has merit of self-start ability, i.e. no risk of start-up failure, whereas the ASyMT has advantage of low iron loss, i.e. low iron loss density on stator and rotor. Prototypes are manufactured to confirm and verify the predicted results and the test results prove the correctness of the analyses.

An analytical technique for predicting and optimising the open-circuit magnetic field in brushless surface-mounted permanent magnet (PM) machines with novel two-segment Halbach array has been presented. For the maximum fundamental air-gap flux density, the optimal magnetisation angle has been analytically derived. The effect of the rotor core on the fundamental air-gap flux density in the machine has been investigated. In addition, the proposed analytical technique can also predict the induced back-electromotive force and the electromagnetic torque. The analytical results show that the electromagnetic performance can be significantly improved for the proposed two-segment Halbach array compared with the conventional two-segment Halbach array. Predicted results have been validated by the finite-element analyses for 9-slot/8-pole slotless/slotted brushless PM machines.

This study presents the operation of a synchronous reluctance motor drive under a sustained voltage dip condition while being connected to a weak grid. In the presence of an input voltage dip, motor may not be able to produce sufficient torque and maintain its original speed. A new technique is proposed in this study to maintain the desired reference torque and speed during a sustained voltage dip. The proposed technique is realised by evaluating mathematically the motor‘s allowable voltage dip margin corresponding to an operating point pertaining to a particular torque and speed in the current locus diagram of the motor. With prior knowledge of the voltage dip margin for every operating point in the current locus diagram, it would be possible to retain the same reference torque and speed by moving to a new operating point, which can be with lesser or greater as compared to the initial operating point, in case a voltage dip greater than the tolerable margin occurs. To start with, voltage dip margin has been derived theoretically and the operation of the motor is investigated by deliberately introducing a voltage dip. The proposed methodology has been verified through simulations and experiments in this study.

Due to the convenience and long travelling distance, electric bicycles (EBs) are becoming more and more popular. Charging EBs with inductive power transfer (IPT) technology can free people from wearisome plugging actions and avoid electric shock hazards. However, the cost, including component cost and control cost, is a big challenge for the extensive promotion of the IPT charging systems (IPTCSs) for EBs. This article proposes an IPTCS using primary-side detuned series-series (SS) compensation topology, cancelling control scheme and reducing the component cost. With the proposed parametric design method, the IPTCS can operate with variable charging current according to the variable equivalent resistance of a battery. Besides, the inductive input impedance is guaranteed to achieve soft switching for the high-frequency inverter. An experimental setup is constructed to validate the proposed method. The performance shows that the charging current decreases from 1.8 to 0.1 A, and charging voltage increase from 42.23 to 54.01 V during the whole charging process, where the maximum efficiency of the IPTCS can reach up to 92.8%. The results demonstrate the proposed IPTCS is a cost-effective and potential solution for charging EBs.

High-voltage direct current (HVDC) system is difficult to proliferate due to the absence of a useful brake for the HVDC circuit breaker. To overcome this problem, this study proposes a useful brake, termed as an Eddy current brake (EB). A time-consuming time step analysis using the finite element method (FEM) is required to analyse the EB. To address this problem, a rapid and accurate analysis method is proposed using the equivalent circuit model, equation of motion, and the Runge–Kutta method. This technique is termed as the EER method in this research. The characteristic of the EB is analysed by using the proposed EER method and the results are compared with those of the 2D FEM analysis. The usefulness of the proposed EER method with regard to accuracy and rapidness is confirmed via 2D FEM analysis.

This study conducts a deep research on a line-start permanent-magnet synchronous motor (LSPMSM) with a composite solid rotor through detailed analyses of two sets of intrinsic motor parameters, i.e. (i) the flux linkages stemming from permanent-magnet (PM) poles, or the so-called PM flux linkages, and (ii) the magnetising inductances related to the stator–rotor magnetic couple. The analyses proceed by separating the motor starting process into a series of sub-states with different slips. At each sub-state, the PM flux linkages and magnetising inductances are both susceptible to the varying saturation of motor cores and hence perform as time-dependent quantities alternating exactly in the slip frequency. Accordingly, these parameters are determined as combinations of cosine functions indicating the quantity alternation, by which the rotor resistances and self-inductances are obtained at the same time. Assembly of all the confirmed motor parameters generates an analytical model of the studied LSPMSM. Responses of this model stay totally in good agreement with those from the finite-element method, and the close result correlation offers an effective validation of the analyses presented in this work.

Brushless doubly-fed induction machine (BDFIM) has recently gained considerable research interests due to its promising features when incorporated as wind generator or variable speed drive. The BDFIM has two three-phase stator windings with different pole-pair numbers and excitation frequencies. The performance of the machine is based on the magnetic cross-coupling of rotating fields produced by the stator windings through a special squirrel cage rotor. Contrary to the conventional induction machine (IM), the rotor slip and frequency are high throughout the operating speed range. Hence, the rotor core loss cannot be ignored in the steady-state analysis. Although the core loss components have much more study of BDFIM. In this study, analytical expressions are individually derived for a number of core loss components caused by the complicated nature than those of an IM, the precise calculation of these components is important especially on the efficiency each stator winding field. Then, the modified steady-state electric equivalent model is developed by considering the components. The experiments and finite element analysis based on a 3 kW prototype BDFIM verify the accuracy of the proposed model.

In this work, the massive modelling and computation costs required by the calculation of the magnetic leakage coefficient were avoided by using the three-dimensional finite element method (3D-FEM) in the initial design and optimisation of hybrid magnetic couplers (HMCs). The equivalent magnetic circuit network model of HMCs was established, and the equivalent reluctance of the model was calculated to obtain the analytic expression of the magnetic leakage coefficient of HMCs. A set of 1:2 prototypes was designed and manufactured. Simulation analysis and experimental tests were conducted to verify the correctness of the calculation of magnetic leakage. The calculated and experimental values of the magnetic leakage coefficient and the 3D-FEM were in good agreement. The output torque value of the HMC was analysed and calculated by considering that the air-gap leakage was closer to the test value and was more accurate than the value calculated without considering the air-gap leakage effect. This study provided a theoretical reference for the design and investigation of HMCs.

Accurate and fast computation of electric fields is of great interest in transformer design. This article presents a fast and precise method of computation of electric field of transformer windings based on the boundary element method and integral equations approach. Additionally, computation of the capacitance matrix of a transformer geometry is presented. Proposed methodology depends on the knowledge of the transformer geometry. Improvement in computational costs and memory requirements of the developed electrostatic solver is achieved by implementation of the adaptive cross approximation algorithm. Results are benchmarked against commercial software based on the finite element method and applicability of the developed solver is proven.