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The purpose is to present a sensorless control method by which high‐resolution rotor position information is estimated and used for phase‐advancing operation of a high‐speed permanent magnet (PM) brushless DC (BLDC) motor.

The proposed sensorless control approach uses hardware to observe the flux vector which is excited by rotor magnets. It can provide the rotor position which is the same as the phase angle of the observed flux vector.

High‐resolution rotor position signal of the BLDC motor for dynamic phase‐advancing control cannot be directly obtained from the conventional Hall‐effect sensors, or via the traditional back‐EMF‐based sensorless control strategies in which the back‐EMF may be even undetectable at high‐speed. The proposed rotor‐flux‐observer (RFO)‐based sensorless control method overcomes these problems, and meanwhile provides high‐resolution rotor position information for the phase‐advancing purpose.

The RFO‐based sensorless control is traditionally applied to PM brushless ac (BLAC) operations, where the motor voltage vector can be calculated from the inverter switching status. However, this is not readily applicable to a BLDC motor since the voltage of the floating phase cannot be calculated. Moreover, during high‐speed operation, the microprocessor may not be sufficiently fast to calculate the high‐resolution rotor position. Therefore, in this paper, it is proposed to use hardware to observe the rotor‐flux‐vector. The microprocessor only samples the vector's α‐ and β‐components and calculates the phase angle, hence, its burden is low. The proposed method is validated with a 1.8 kW 85,000 rpm BLDC motor system.

The aim of this paper is to present a new sensorless control strategy using a flux observer, which is particularly designed for taking into account the rotor saliency and winding inductance variation in an interior permanent magnet synchronous motor (IPMSM).

In a PMSM, the magnets‐excited flux‐linkage, i.e. the rotor flux‐linkage, can be expressed as a vector. Its phase angle stands for the rotor position. Therefore, if this vector is estimated with an observer, the rotor position can be obtained without a position sensor, consequently, sensorless control can be realized. The main object of this paper is to establish and implement a model of rotor flux observer, specifically for IPMSM.

The flux observer model is built on the d‐q‐0 frame, using unequal values of the d‐axis inductance L_d and q‐axis inductance L_q to represent the IPMSM rotor saliency. Its digital implementation is proposed, whilst the sensorless control strategy is experimentally verified.

Insignificant error exists in the estimated rotor position, probably due to the non‐sinusoidal variation of winding inductance. Further improvement of the observer model is preferable.

In previous works, the rotor flux observer is only applied to surface‐mounted permanent magnet synchronous motors (SPMSM) in which the winding inductance is constant. However, the proposed observer can deal with the rotor saliency and inductance variation in IPMSM, whilst its digital implementation is also new.

The purpose of this paper is to focus on various control strategies for permanent magnet synchronous generator (PMSG) systems, in order to stabilize the dc link output voltage over a wide operation speed range.

Two control methods, namely, the flux regulation control (FRC) which adjusts the stator flux linkage and then indirectly stabilize the dc link voltage, and the direct voltage control (DVC) which directly stabilize the dc link voltage by regulating the power angle, are proposed in this paper. Both methods can be realized by either approach of the conventional space vector pulse width modulation (SVPWM) or the proposed single voltage vector modulation (SVVM).

The FRC can optimize the field in the PMSG, however, the realization is complicated. The DVC need not estimate and regulate the stator flux linkage, hence is easy to implement. On the other hand, the SVPWM can provide smooth armature current and dc link voltage, while the SVVM applies only one voltage vector during each control cycle, hence, is simple to realize and requires the minimum switching on the PWM rectifier. All cross-combinations between the two control methods and the two realization approaches work well.

The proposed FRC and DVC methods are simpler than the conventional field oriented control, while the proposed SVVM is a novel and efficient approach to generate the PWM status. Optimal cross-combination, either of SVPWM-FRC, SVVM-FRC, SVPWM-DVC and SVVM-DVC, can be chosen to satisfy the system characters and requirements.

The purpose of this paper is to propose a new outer‐rotor permanent‐magnet flux‐switching machine (ORPMFSM) for electric vehicle (EV) in‐wheel propulsion. The paper documents both the design procedure and performance investigation of this novel machine.

The topology and preliminary sizing equations of the ORPMFSM are introduced. The rotor poles are optimized, whilst the machine losses are particularly investigated, using 2‐D finite element analysis (FEA).

An ORPMFSM, with 12 stator poles and 22 rotor poles, is most suitable for the proposed EV application. The analytical sizing equations are quite efficient with a sufficient accuracy for the preliminary design. The optimal rotor pole width from the FEA results is nearly 1.3 times the original value which was proposed in early literatures. The efficiency of the proposed machine under rated load is slightly low, as a result of significant eddy current losses in the permanent magnets. The losses can be effectively suppressed with the technique of magnet segmenting. The predicted outstanding performance implies that by adopting magnet segmentation the proposed machine is a leading contender for EV direct drives.

The outer‐rotor structure of PMFSM was not addressed in early literatures. This paper provides designers with the technical background and an alternative candidate for the EV propulsion.

The purpose of this paper is to comparatively study a synchronous reluctance machine (SynRM) and a permanent magnet assisted synchronous reluctance machine (PMASynRM) as alternatives of the interior permanent magnet synchronous machine (IPMSM), and to investigate the performance and conclude both advantages and disadvantages.

A unified mathematical model is established for the IPMSM, SynRM and PMASynRM. Then finite element method (FEM) is used to compare the electromagnetic performance. Permeability-frozen method is utilized to distinguish basic electromagnetic torque and reluctance torque.

The PMASynRM can improve the power factor of the SynRM, overcome the drawback of the IPMSM in the high-speed flux-weakening region and is more proper to operate over a wide speed region. The SynRM is mechanically robust for lacking of the permanent magnets, and the PMASynRM can keep similar rotor stress as the SynRM by optimizing the magnets. Assembly of the SynRM is the simplest, and the economic performance of the SynRM and PMASynRM could be much better than the IPMSM which even uses ferrite magnets.

The SynRM can produce identical torque and efficiency compared with the IPMSM except the poor power factor. The poor power factor could be improved by adopting the PMASynRM, which is proved to be able to act as an alternative of the IPMSM for low-cost high-performance application.

This paper provides the theoretical model of the IPMSM, SynRM and PMASynRM in a unified format. The electromagnetic, mechanical and economic performances of the three kinds of synchronous motors are compared comprehensively. Then, both the advantages and disadvantages are summarized.

The purpose of this paper is to investigate the effect of the interlocking process on the iron loss in the lamination core and to increase the efficiency of electrical machines.

A 3D electromagnetic model of the interlocking dowels is proposed in order to simulate the eddy current distribution in the lamination core. Considering the time-consuming of the 3D finite element method (FEM), a 2D electromagnetic model is then proposed based on the 3D model. Influence of the interlocking process on the motor performances is analyzed with 2D FEM, considering the electrical connection of the dowels and the magnetic property deterioration of the electrical steel sheets.

The interlocking process removes the insulation between the laminations at the cut-edges of the interlocking dowels, causing extra eddy current loss in the lamination core. The effect of the interlocking process is dependent on the number, location and size of the interlocking dowels.

The interlocking dowel model is established in order to simulate the effects of the interlocking process. By using the FEM calculation, optimal solution is discussed to minimize the undesired effect of the interlocking dowels.

In this paper, the FEM model of the induction motor with interlocked stator core is first established, then simulation analysis is implemented. Results shows that choosing a proper number of interlocking dowels with suitable location and size can reduce the extra loss.

The purpose of this paper is to study a woodworking machine, in which a linear induction motor (LIM) is applied to feed the wood to be processed into the cutting saw. The LIM is optimally designed and the whole drive system is controlled by a programmable logic controller (PLC) to meet the industrial demands.

Since the operation range is short, the LIM mainly works at the transient state of quick start and quick brake. Hence, the thrust force with a large slip ratio (hereafter called the starting thrust) is one of the most important issues in the LIM design. Finite element method is used to optimize the starting thrust while taking a specific variable voltage variable frequency (VVVF) drive into account.

The LIM system directly drives the machine workbench where the wood is placed, eliminating the requirement of manpower to push the wood through the cutting saw, hence, greatly reduces the operation hazard. It has a higher reliability and longer service life than the conventional drive system employing a rotary motor with a ball screw mechanism.

The LIM is an attractive candidate for the woodworking machine application, which can replace the complicated and relatively low-efficiency mechanism of rotary motor and ball screw. High starting thrust can be achieved by optimizing the LIM design, whilst the specific VVVF control is essential to ensure a good drive performance. The PLC is competent for both human-machine interface (HMI) and control of the inverter-fed LIM system, and is of high reliability in industrial environment.

The purpose of this paper is to evaluate the cogging torque in a surface-mounted permanent magnet (SPM) machine with both uniformly and non-uniformly segmented stator cores and to find out the optimal solution of stator core segmenting.

The cogging torque with segmented stators is synthesized from a single slot model, and analytical prediction is given to analyze the cogging torque with both uniformly and non-uniformly segmented stators. Finite element method (FEM) is used to figure out the electromagnetic field and validate the analytical prediction. Moreover, models with various shapes and positions of connecting tongues between the stator core segments are explored to achieve the optimal design.

The cogging torque is found to be greatly related to the number of segments and the electrical angle between adjacent additional air gaps caused by the tolerance of stator segments. Different shapes of the connecting tongues are tested and proved to be of great importance to the flux density, both radial and tangential, and therefore affect the cogging torque. Finally, position of the connecting tongues is perceived to have little influence on the performance of machine.

By utilizing analytical prediction and FEM calculation, the optimal solution is discussed to minimize the cogging torque in the SPM machine from the perspective of the stator core segmentation.

This paper establishes formula of cogging torque with segmented stators and predicts the variation of cogging torque with analytical method. Besides, different combinations of segments are compared and measures to reduce the cogging torque produced by the segmentation are proposed.

The purpose of this paper is to focus on the machine design and control strategy of the permanent magnet synchronous generator (PMSG) system, especially utilized in variable speed applications, in order to stabilize the output voltage on the dc link over a wide speed range.

Different ac/dc power converter topologies are comparatively studied, each with an accordingly designed PMSG, so as to investigate the influence of the armature winding inductance as well as the relationship between the PMSG and power converter topologies.

Pulse width modulation (PWM) rectifier is preferable for the said application due to its good performance and controllability. Moreover, by employing the PWM rectifier, relatively large inductance of the PMSG is considered for both short-circuit current reduction and field regulation.

Field-regulating control is realized with a space vector PWM (SVPWM) rectifier, which can weaken the PMSG magnetic field during high-speed operation, while even properly enhance the field at low speed, ensuring a small change of the PMSG output voltage and a stable dc voltage.