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Homopolar inductor machine (HIM) has caught much attention in the field of flywheel energy storage system (FESS) due to its merits of robust rotor, brushless exciting, high reliability, etc. Compared with permanent magnet HIM (HIM-PM), the HIM with field winding (HIM-FW) can effectively eliminate the idling loss caused by the no-load magnetic field by cutting off the excitation current, while the charge/discharge efficiency of HIM would be decreased due to the copper loss of field winding. To address this contradiction, a novel PM HIM with mechanical flux modulator (HIM-MFM) is proposed to achieve low idling loss and high charge/discharge efficiency. Firstly, the special structure and operation principle of the HIM-MFM are investigated. Afterwards, the characteristic of equivalent magnetic circuit of the HIM-MFM is analyzed and several key structure parameters of it are optimized. Moreover, the electromagnetic performance indexes of the HIM-MFM, including back-EMF, flux weakening ability, losses, etc. are fully analyzed. Finally, a prototype of the HIM-MFM is designed, manufactured, and tested. Experiment results confirm those obtained by simulations. Results show that the proposed HIM-MFM inherits the merits of high charge/discharge efficiency of HIM-PM and almost no idling electromagnetic loss of HIM-FW.

Homopolar inductor machine (HIM) has been applied in the field of flywheel energy storage system (FESS) due to its merits of simple structure, high reliability, and low idling losses. However, the HIM features unipolar air-gap flux density, which makes its power density lower than that of the electrical machine with bipolar air-gap flux density. Addressing this issue, a novel outer rotor homopolar inductor machine (OR-HIM) is proposed in this article. First, the special structure and operation principle of the OR-HIM are illustrated. Then, the unit motors of the OR-HIM are obtained and investigated based on the magnetic equivalent circuit method to facilitate the design. Moreover, the performance indexes, including power density, output characteristics, losses, and rotor stress of the OR-HIM, are fully analyzed. Finally, a 13-kW prototype is designed, manufactured, and tested. The back electromotive force, load voltage, output torque, and efficiency are measured and compared with those obtained by the finite element analysis. The results indicate that the proposed OR-HIM is a promising candidate for the application of FESS.

Brushless structure is beneficial for air-core compensated pulsed alternator (ACPA) because its field current and rotation speed are too large for the slip rings and carbon brushes. To achieve the brushless structure, a cascaded brushless self-excited ACPA (CBSACPA), which consists of an exciter and a generator in cascade, is proposed, in this article. The exciter and generator have a common rotor. A novel squirrel-cage rotor winding (SCRW), which can eliminate the end winding compared with conventional wound rotor winding (WRW), is proposed to simplify the rotor structure and improve the performance. First, the structure of the CBSACPA with the SCRW is introduced. Second, the operation principles of the machine are elaborated. Third, the dynamic mathematical model is presented. Fourth, the operation principles are demonstrated by the finite-element method. In addition, the performance of the SCRW is compared with the WRW as well. Finally, a prototype of CBSACPA is developed and tested to validate the analyses and simulations. In conclusion, this study gives detailed introduction, analyses, and validation about the CBSACPA, which provides a new solution to achieve a brushless structure for the ACPA.

Homopolar inductor machine (HIM) has been applied in the field of flywheel energy storage system (FESS) due to its merits of simple structure, brushless exciting, and low idling losses. The rotor of HIM not only plays the role of energy conversion but also serves as a flywheel to store kinetic energy, which is different from other electrical machines used in FESS. Meanwhile, the HIM usually operates at high speed to improve the power density and storage energy. To obtain good performance and high reliability, the design and optimization of HIM should consider multiphysics, including storage energy, electromagnetic performance, rotor stress and dynamics, and so on. However, the existing researches mainly focus on the analysis of electromagnetic performance and lack multidisciplinary design. To solve this problem, a multidisciplinary design method of HIM is proposed and investigated. First, the operation principle of HIM is illustrated, and the multidisciplinary design method is proposed. Then, the storage energy, electromagnetic performance (including no-load air-gap flux density, saliency ratio, torque, and electromagnetic power), rotor stress, and modal of HIM are deeply analyzed according to the proposed design flow. Finally, a prototype of HIM is manufactured and tested. The results calculated by finite-element analysis are validated by experiments. The design method proposed in this article provides a straightforward procedure for the multidisciplinary design of HIM.

The surface-mounted permanent magnet linear synchronous motor (PMLSM) is a good candidate for the Electromagnetic Launch System due to its merits of high-power density, power factor and efficiency. However, this kind of machine needs a lot of permanent magnets (PMs) on the long stator, which is costly. To solve this problem, a novel PMLSM is proposed in this paper. The stator of novel PMLSM has the consequent poles structure and the mover of novel PMLSM has two iron cores, which sandwiches a mover PM. Firstly, the structure and operation principle of the proposed PMLSM have been investigated. Then, the analytical calculation of thrust and detent force is analyzed and the structural parameters of the motor are optimized for larger thrust and less detent force. Finally, for a fair comparison, the proposed motor is designed and built based on an existing PMLSM with similar electromagnetic and geometrical parameters. The thrust performance indexes of the novel PMLSM are estimated and compared with the conventional surface-mounted PMLSM, which indicates that the proposed PMLSM can keep similar performances with the exciting PMLSM. Moreover, it has a simple structure, less thrust ripple and can save many PMs, which can help reduce costs.

Homopolar inductor machine (HIM) has a wide range of applications in the field of flywheel energy storage system and ship propulsion due to its merits of simple structure, brushless exciting, and low idling losses. However, the three-dimensional finite element method (3-D FEM) is mainly used to investigate the electromagnetic performance indexes of HIM due to its intrinsic 3-D flux density distribution, which is time-consuming. To facilitate the analysis of HIM, an analytical method (AM) is necessary, especially in the initial design stage. Hence, this article presents an AM for analyzing the electromagnetic performance of HIM. First, the structure and operation principle of HIM are illustrated. Second, the magnetic equivalent circuit of HIM is built considering the saturation of stator and rotor core. Third, the air-gap permeance function is obtained considering the affection of stator and rotor slots. Finally, the magnetomotive force, air-gap flux density, back electromotive force, inductances and electromagnetic torque of HIM are calculated, then validated by 3-D FEM and corresponding experiments. The results indicate that the proposed AM can provide reasonable results to estimate the electromagnetic performance of HIM, which would be helpful for the analysis of HIM.

© 1972-2012 IEEE. A novel hybrid excited asymmetric stator pole doubly salient machine (HEASPDSM) is proposed in this paper. The new topologies and operational principle are first investigated by using a simplified equivalent magnetic circuit model. The harmonic components of air-gap flux density are then analyzed. The influence of key structural parameters of the proposed machine on the flux regulation ability and torque is studied. A full comparison on main electromagnetic performance indexes of the proposed 12/7 (stator/rotor poles) HEASPDSPM and several traditional doubly salient machines is presented. A prototype is fabricated and tested to validate the theoretical analysis. The results well demonstrate that the HEASPDSPM possesses various merits, such as strong flux regulation capability, high torque density, low cogging torque, and low torque ripple.

Air-core compensated pulsed alternator (ACPA) has been applied to the field of pulsed power technology, especially electromagnetic launch. The high-field current and the rotating speed of the ACPA bring the benefits of high power and energy density, but also make it suffer from low reliability and poor performance due to the serious heat and wear in the slip rings and brushes. To solve this problem, a novel brushless self-excited ACPA (BSACPA) is presented in this paper. It consists of two submachines in cascade, namely, an exciter and a generator, for which the air-gap flux rotation directions are opposite. The rotor windings are specially arranged and adopt the principle of negative sequence alternate current excitation, thus eliminating brushes and slip rings, and no rotary rectifier diode is needed. First, the structure and the operation principle of the BSACPA are described. Second, the magnetic field distribution and the coupling between the two submachines are analyzed. Third, the mathematical model of BSACPA is established. Finally, the validity of its operation principle is verified by finite-element and circuit analyses. In conclusion, BSACPA achieves the brushless structure and provides a new solution to improve the performance and the reliability of a conventional ACPA.

Pulsed power technology is widely used in medical treatment, military, and scientific research, such as laser burst and electromagnetic launch. Compensated pulsed alternator (CPA) is a kind of device generating that pulsed power. One of the shortages for the air-core pulsed alternator is the huge excitation loss. In order to solve the problems, a multidisk axial flux CPA (MAFCPA) is proposed, which replaces the excitation windings with permanent magnets, saving the self-excitation process. In addition, multidisks are designed, especially to reduce subtransient reactance when the CPA discharges, which contributes to increasing the discharging current. This paper mainly focuses on researching the feasibility of MAFCPA in aspects of thermal issues, rotor statics, and dynamics problems. First, the topology and principle of MAFCPA are introduced, and the properties of the materials are listed as well. Second, the loss of discharging is calculated and the temperatures of both stator and rotor are solved. Then, the maximum stresses of different materials are obtained. Afterward, the critical speeds are researched in order to avoid resonance. Finally, the conclusion is made that MAFCPA can work safely under a speed of 10000 r/min and supply a pulse of over 50 ms.

The compensated pulsed alternators (CPAs) have good applications in high-energy lasers, electromagnetic rail guns, and other electromagnetic launch devices. Among various electrical machine topologies, homopolar inductor alternators (HIAs) have attracted interest as CPAs due to their merits of simple and reliable structure, brushless excitation, and high-speed operation. However, the length of the conventional HIA is difficult to expand because it is limited by the rotor diameter, and the rotor diameter is restricted by the maximum speed of rotor tip, which results in low-energy storage capacity of a single machine. Besides, HIA suffers from the relatively low-power density due to its unipolar air-gap flux density (UAFD). To solve these problems, two novel HIAs with multistage stator cores (HIA-MSCs) are proposed in this paper. One is HIA with UAFD (HIA-UAFD) and the other is HIA with unipolar and bipolar air-gap flux density (HIA-UBAFD). First, the structure and operation principle of HIA-MSCs are illustrated. Then, the key parameters of HIA-MSCs are derived, and the corresponding models are built. Finally, the electromagnetic performances of HIA-MSCs are investigated by 3-D finite-element analysis method. Compared with HIA-UAFD, HIA-UBAFD has relatively higher discharge current and output power, which indicates that HIA-UBAFD is a better candidate for the pulsed alternator.

In recent years, several novel homopolar inductor machine (HIM) topologies, such as rotors with the rectangular, arc-shaped, sinusoidal and triangle rotor slots, are developed. However, the influence of different rotor slots on the performance of HIM is not clear, and there is no basis for selecting rotor slots. Addressing this issue, a comprehensively comparative studies of these topologies with different rotor slot shapes are implemented. Firstly, the topology and operation principle of the HIM are illustrated. Then, the influences of rotor slot shape on the performance including the no-load air gap flux density, back electromotive force, inductance, torque, torque ripple and losses are systematically studied. Moreover, the stress distribution, modal and rotary inertia of rotor with four different rotor slots are analyzed. Based on the above analyses, the HIM with arc-shaped rotor slots is selected and its prototype is developed. Some electromagnetic performance indexes are tested to verify the rationality of analyses. This work clearly points out the advantages and disadvantages of HIMs with different rotor structures, which could be good reference for the selection of rotor slot shape.

Permanent magnet synchronous machines (PMSM) are widely used due to their small size and good running performance. However, PMSM have the disadvantages of multivariable and strong coupling, which make it difficult to design the regulator parameters. To solve this problem, this paper studies the use of three-vector model predictive current control (TV-MPCC) in PMSM. The traditional TV-MPCC uses speed sensors, which increases the cost and installation difficulty. The extended Kalman filter (EKF) algorithm which is applied for detecting rotor position and speed is proposed in this article. By comparing the traditional TV-MPCC algorithm with sensorless algorithm, the results indicate that there is no significant difference between sensorless algorithm and the traditional MPCC algorithm, sensorless algorithm has an analogous dynamic and steady-state performance.

© 1972-2012 IEEE. This article presents the design and analysis of a 12/7 (numbers of stator/rotor poles) hybridly excited asymmetric stator pole doubly salient machine (HEASPDSM) with a main focus on the special topology and operational principle by using the analytical and 2-D finite element analysis. A full comparison is conducted on the average torque, torque ripples, no-load back electromotive force and flux regulation capacity under the condition of different structural parameters, which can provide good references to the machine design. A 12/7 HEASPDSM is designed and the main performance indexes are analyzed in detail. Based on the parameters, the performance of 12/7 HEASPDSM is compared with traditional 6/7 doubly salient permanent magnet machine (DSPMM) with the same volume and thermal load. Finally, a prototype of the 12/7 HEASPDSM is manufactured and tested to validate the theoretical analysis. The results fully demonstrate that the HEASPDSM possesses the merits of strong flux regulation capability, higher torque density, and wider constant power speed range benefitted from the dc field winding than the traditional DSPMM.

Doubly salient permanent magnet machine (DSPMM) has received extensive attentions recently due to its simple structure, high reliability, high torque density, etc. An improved 4/4 stator/rotor single-phase asymmetric-stator-pole doubly salient permanent magnet machine (SP-ASPDSPMM) is proposed in this paper. Firstly, it investigates the topologies and operation principle based on graphical description and torque expression. Then, the effect of main structure parameters on the torque is studied based on two-dimensional finite element algorithm (2-D FEA). And then, comprehensive comparison on main electromagnetic performances for the two machines is made. Finally, one prototype for the improved structure is made and tested. It indicates that lower cogging torque, lower torque ripple and stronger starting performance can be obtained by the improved structure. The theoretical results are well validated by the experiments.

The homopolar inductor machine (HIM) is of particular interest in the field of flywheel energy storage system, where it has the potential to significantly reduce self-discharge associated with magnetic losses. However, the conventional HIM suffers from low power and torque density due to its unipolar air-gap flux density. Besides, the air-gap flux density of HIM is limited by the cross section of rotor, and the rotor diameter is limited by the maximum tip speed of the rotor. Thus, the maximum effective length and diameter of rotor should be within a certain range, which constrains the output power and stored energy of the HIM. To solve these problems, a novel multi-unit out-rotor HIM (MO-HIM) with bipolar air-gap flux density is proposed in this paper. First, the structure and operating principle of MO-HIM is illustrated. Then, the characteristics of the proposed machine are analyzed, indicating that MO-HIM can be regarded as a superposition of multiple unit machines. Finally, to verify the superior performances of the proposed MO-HIM, it is compared with a unipolar out-rotor HIM with multi-segment stator cores in terms of air-gap flux density, back electromotive force, and output torque. Results show that the proposed MO-HIM has larger fundamental air-gap flux density, higher power, and torque density.

A vehicular generator has stringent requirements on its weight and volume. As a combination of permanent magnet and electric excitation motor, hybrid excitation machine could meet the requirements of vehicular generator, with small size, light weight, adjustable output voltage. In this paper, an axial flux stator partition hybrid excitation brushless synchronous generator (ASHG) is proposed. First, the structure and operation principle of ASHM is illustrated. Afterwards, the shape of the magnetic pole is optimized to obtain the air-gap flux density with low harmonic content. Moreover, the regulation performance of the magnetic field and output voltage are investigated by three dimensional finite element analysis (3D FEA). The result indicates that ASHG has a high performance of adjusting terminal voltage. It can improve the generator efficiency, power density and stability comparing with the conventional vehicular generator.

Traditional moving-magnet transversal-flux linear oscillatory machines (MTLOM) suffer from high fabrication difficulty and cost, low robustness and reliability, and low material utilization ratio, etc. In this paper, a novel stator-magnet moving-iron transversal-flux linear machine (SMTLOM) is proposed, with magnets inserted into the stator yoke (rather than mounted on stator poles) and mover composed of iron core only. First, the topology of proposed SMTLOM is described, as well as its operation principle. Then, the comparison rules are built to make fair comparison between the conventional MTLOM and the novel SMTLOM, from the perspective of practical application, including the same maximum size limitation, output thrust, and thermal source. By using a three-dimensional finite-element analysis (3-D FEA), comparisons of some key performance indexes, such as back electromotive force, thrust per coil length, thrust per magnets volume, thrust per machine volume, temperature distribution, material cost and structure reliability, etc., are made between these two types of machines. The results from 3-D FEA demonstrate that the novel SMTLOM has enjoyed merits of lower fabrication cost and weight, much higher reliability, thrust density, material utilization ratio, etc., which indicate that the novel SMTLOM is more suitable for driving compressor and easier for mass production.

The homopolar inductor alternator (HIA) has some merits over classical machines for applications such as a high-temperature superconducting machine and as flywheel energy storage system. For the design of HIA, the back electromotive force (back-EMF) and air-gap flux density are two key parameters. Due to the intrinsic three-dimensional (3-D) magnetic circuit structure, 3-D finite-element analysis (FEA) is required for accurate modeling of HIA, which is, however, very consuming. To solve this problem, a 2-D analytical model is proposed in this paper. First, the method of air-gap flux density spatial overlay analysis is illustrated. Based on it, the structure and equivalent principle of 3-D converting to 2-D model of HIA are investigated. Finally, the analytical model is applied to HIAs with different rotor structures to prove the accuracy of the proposed model. An experimental platform is built to verify the effectiveness of this model. The results indicate that the proposed model can accurately calculate the back-EMF and air-gap flux density. Meanwhile, it takes much shorter time than 3-D FEA method does.

The torque ripple is a main source of the noise and vibration which has a considerable effect on the performance of the machine. A design technique, tooth notching, which was extensively used in permanent magnet machines, has been innovatively applied to a wound-rotor brushless doubly-fed machine (BDFM) to reduce the torque ripple. First of all, the winding structure, the winding space harmonics and magnetic fields of the stator and the rotor were studied. Then, general analytical expressions of the electromagnetic torque (EMT) for the BDFM were deduced. Finally, prediction of the results was verified by several models which were calculated by the finite-element analysis method, meanwhile, the influences of different tooth-notching structures and the notch depth on the EMT were investigated. It is shown that the torque ripple can be reduced by the suggested design with small increment of the magnetic field saturation and the currents of the control winding and the rotor winding.

© 2017 IEEE. While having various desired merits of high structural robustness and thus reliability, high thrust density, low fabrication cost, and so on, the stator-magnet moving-iron transverse-flux linear oscillatory machine suffers from high consumption of rare-earth magnetic material (high material cost) and heavy flux leakage at the stator outer region (underutilization of permanent magnets). To mitigate the demerits, a novel stator-magnet moving-iron transversal-flux hybrid-flux-path linear oscillatory machine (SMTHLOM), with additional back iron and auxiliary radially magnetized ferrite magnets, is proposed in this paper. The topology and operational principle of the proposed SMTHLOM are explained in detail. The 3-D finite-element analysis is introduced to investigate the sensitivities of main structural parameters, which enables the selection of optimal dimensions. Based on a set of comparison rules, a comprehensive comparison was conducted between these two topologies on various key indicators, such as the back electromotive force, thrust, and thermal distribution. The simulation results show that the SMTHLOM is low cost and small stator outer flux leakage, and thus is more suitable for some applications, e.g., fridge compressors, requiring low cost and high thrust density.

© 1965-2012 IEEE. In this paper, one novel heteropolar radial hybrid magnetic bearing (HRHMB) is proposed for flywheel energy storage system. First, its structure and working principle are introduced in detail. Then, its fundamental equations are derived based on magnetic circuit model, such as displacement stiffness, current stiffness, and load capacity. Furthermore, its suspension performance and magnetic coupling are analyzed based on the 2-D finite-element analysis. Finally, the comparison of main performance indexes between the proposed HRHMB and conventional one under the same constraints is made. It indicates that the displacement stiffness can be reduced by the novel structure. In addition, the rotor core loss of the novel HRHMB is just 22.53 W, which is only 41.6% of the conventional eight-pole HRHMB with the same load capacity.

Homopolar inductor alternator (HIA) has been widely used as a high-speed pulsed alternator in the electromagnetic launch field due to its merits of high-speed operation, power density, and reliability. To achieve the above-mentioned merits, a high-strength and high-stiffness solid rotor is usually adopted in the HIA. However, the solid rotor would be subject to high eddy current loss. Some works have been done to analyze the rotor eddy current of the HIA, while the research on analytic calculation and reduction of rotor eddy current loss is relatively few. In this paper, an analytic calculation method is established to calculate no-load rotor eddy current loss for HIA, which is validated by the finite-element analysis and corresponding experiments. Besides, to minimize the rotor eddy current loss, a simple method, by slitting the rotor tooth, is proposed. Moreover, the influence of circumferential and axial slits on the rotor eddy current loss and air friction loss is comparatively studied. Finally, the influence of the width, depth, and number of slits on the eddy current loss is investigated. It is shown that the circumferential slits have better performance than that of axial slits to reduce the eddy current loss.

The pulsed high-power supplies in this paper employs a homopolar inductor alternator (HIA) as the motor/generator integrated energy storage pulsed alternator. Lumped parameter design equations are developed, which is used to establish the mathematical model of the HIA, and the analytic calculation method of inductance matrix is derived. Prototype flywheel energy storage was built, and the basic structure of HIA is analyzed by using finite-element method (FEM). This paper proposes a simplified equivalent 2-D salient-pole synchronous generator model to simplify the 3-D FEM of HIA and investigates the motor control method of HIA based on the simplified 2-D equivalent model. The experiments were conducted for speed up to 8000 rpm and the six-step inverter drive strategy presented in this paper achieves the motor/generator integrated control on inductor energy storage pulsed alternator (IESPA). Most experimental results were in line with designed value.

Pulsed alternators have the merits of high energy and power densities, which are applied to a wide range of applications, such as the electromagnetic launch, the pulsed laser, and the pulsed high magnetic field. A new type of high-speed and high-frequency pulsed alternator integrating an alternator and a motor, is proposed in this paper. A solid rotor which is made of high-strength alloy steel with high yield strength is used in the pulsed alternator, so it can work at a high tip speed. This machine consists of two alternators and a motor which share one rotor and one field winding. According to different voltage levels and operation frequencies, the motor and the alternators with different stack lengths and pole-pairs are designed, respectively. Therefore, it has the abilities of being driven by low-frequency current and discharging high-frequency pulses. In this paper, the basic structure and fundamental of the pulsed alternator are introduced, the specific parameters of the prototype are given, and the performances are verified by the simulation. The results show that the machine proposed in this paper is suitable for the applications that require high-frequency pulsed discharge.

One novel 4/6 stator/rotor single phase doubly salient permanent magnet machine with asymmetric stator poles is proposed in this paper. Design optimization technique based on 2D finite element analysis (FEA) is used to refine the proposed machine. Besides, comparison of electromagnetic performance indexes of the proposed machine with that of traditional 4/6 stator/rotor single phase doubly salient permanent magnet machine with uniformly distributed stator poles is also presented. It indicates that the proposed machine has much higher torque, lower core losses, and higher efficiency than those of traditional one.

A novel brushless self-excited air-core compensated pulsed alternator (BSACPA) is presented in this paper. It consists of two submachines in cascade, among which one serves as an exciter and the other works as a generator. The rotor windings of the two submachines are connected by a reverse phase sequence to realize reversal of the magnetic field. The stator windings are connected by a rectifier to realize the brushless self-excited structure. As an air-core compensated pulsed alternator (CPA) of new topology, it is necessary to derive its mathematical model and carry out a comparative design. Thus, this paper focuses on the detailed design and analysis of a BSACPA prototype, which includes dimensional design and equivalent circuit establishment. In addition, the critical speed is also acquired. Accordingly, the numbers of winding coil turns are designed to increase the discharge current and power based on the theoretical analysis. Finally, the analysis and design are verified by finite-element analysis (FEA).

A novel hybrid excited asymmetric-stator-pole doubly salient permanent magnet machine (HE-ASPDSPMM) is proposed in this paper. Firstly, it investigates the new topologies and operation principle based on simplified equivalent magnet circuit (EMC) model. Then, the harmonic components of air-gap flux density are analyzed in details based on analytic method. And then, the influence of key structure parameters of proposed machines on the flux regulation ability and torque is investigated. Finally, the full comparison on main electromagnetic performance indexes of the proposed 12/7 (stator/rotor pole) HE-ASPDSPMM with those of traditional 6/7 biased flux permanent magnet machine (BFPMM) with doubly salient structure and concentrated windings is presented. It indicates that the proposed machine enjoys the merits of strong flux regulation ability, lower cogging torque, higher torque density, lower torque ripple, etc.

Doubly salient permanent magnet machine (DSPMM) enjoys the advantages of high torque density, simple rotor structure, high reliability, etc. However, the air-gap flux density is difficult to regulate due to that the air-gap magnetic field is produced only by permanent magnets (PMs). Thus, this paper proposes a hybrid excited asymmetric-stator-pole doubly salient machine (HE-ASPDSM) and its air-gap flux density can be regulated easily by controlling the excitation current of field winding. The topologies and operation principle of the HE-ASPDSM are studied firstly based on modern winding theory and two-dimension finite element analysis (2D FEA). Then, the comparison of no-load flux linkage, back electric magnetomotive force (EMF) and air-gap flux density of different topologies is made. Besides, the expression and harmonic components of airgap flux density are also derived based on mathematical analysis. And then, the influence of key design parameters on the cogging torque, flux regulation ability, electromagnetic torque, losses and efficiency is investigated in details. Finally, the analysis of main performance indexes is performed based on the proposed 12/7 (stator/rotor poles) HE-ASPDSM. It indicates that the proposed 12/7 HE-ASPDSM has strong air-gap flux regulation ability.

Homopolar inductor alternator (HIA) has wide range of applications in the field of flywheel energy storage system with the merits of solid rotor structure, brushless exciting and low idling losses. While the design progress of HIA is complex and time consuming due to its three-denominational (3-D) magnetic circuit structure. To solve the above-mentioned problem, a new method to design HIA and the corresponding optimized measures are implemented. At the beginning, the method and principle of superposing the air-gap flux density are introduced. Based on it, the HIA can be equivalent to a wound-field salient pole alternator (WSPA) with two-denominational (2-D) magnetic circuit structure. The HIA is designed according to the design method of WSPA. Meanwhile, the saturation of stator shell and rotor shaft of HIA is considered in the design progress. To facilitate the design, an automatic design program using Monte Carlo search method is developed. Finally, both the effectiveness of this equivalent method and the correctness of automatic design program are validated by finite-element analysis (FEA) and corresponding experiments. The results show that the proposed method would be helpful for the design of HIA.

An air-core pulsed alternator is extremely attractive for driving the electromagnetic launchers. The reason is that the machine can offer high voltage and current performance in a single-element energy storage device, a smooth pulse profile, and naturally cycled current zeros, which can allow for extremely low muzzle currents and simplifies switching requirements. But because of the short history of the air-core pulsed alternator in China, the relevant theoretical research is not enough and the experience in fabrication is absent. It is really necessary to summarize a preliminary design method in order to rapidly determine the size and approximately evaluate the electrical performance of the machine. The optimization will be based on this first-stage design scheme. In this paper, based on the requirements of the railgun, some important design considerations of a seven-phase and six-pole air-core pulsed alternator are presented in detail. In addition, it is significant to obtain the analytical formulas for the first-stage design requiring less costs; these formulas intuitively allow us to expedite the design process and optimize the design scheme. Finally, some basic output parameters of the machine are given for the preliminary design; the designed pulsed alternator will generate 1.4 kV and drive a train of 1-MA pulses into a 5-m railgun, accelerating 200-g masses at 2 km/s.

This paper presents an unexpected fluctuation of voltage for a 30-kW wound rotor brushless doubly-fed machine (BDFM) in a standalone power generation system. To address this issue, an improved method of harmonic injection is introduced. A voltage and current double closed-loop control strategy, based on control winding (CW) current decoupling, is applied through the entire experiment. Consequently, the experimental outcomes are fairly aligned with the dynamic simulations in most conditions. However, the voltage fluctuation in the power winding (PW) can be observed for a certain speed range. Harmonic analysis is then carried out on experimental data of PW voltage and CW current. A pair of interharmonic waves, which are symmetric with respect to the fundamental wave, is demonstrated to exist in PW voltage and CW current. Due to the analysis, these harmonic conjugate waves are caused by the high-order magnetomotive force tooth harmonics and current harmonics within a specific speed range. Accordingly, the control strategy of harmonic injection is employed to effectively eliminate these harmonic conjugate waves. The experimental results further highlight that the voltage amplitude can be maintained with less harmonic contents by our tailored control scheme. In addition, the formation and presence of harmonic conjugate waves may lead to the voltage amplitude fluctuation of BDFM in the standalone power generation system.

The high power pulsed charging power supply is usually necessary for the pulsed power devices with high power repetitive discharge. This paper first introduces a new topology structure of a charge and discharge system for high voltage capacitor and its operating principle, then comes up with technical requirements for the pulsed alternator. Afterward, design features of the inductor pulsed alternator, including the structure, main dimensions, and sizes of rotor teeth and slots are studied, and the main parameters of homopolar inductor pulsed alternator (HIPA) prototype are provided. The choice of rotor material and bearing failure phenomenon are also investigated to find a responsible solution. Finally, the experimental waveforms of HIPA prototype without and rated load when charging capacitor are given. The research shows that the pulsed power supply based on the inductor pulsed alternator is competitive for its high energy storage density, moderate power density, and high reliability, which is suited to the charging power supply of pulsed capacitor.

This paper presents a novel brushless doubly fed alternator (BDFA) based on the differential mode and conducts research on its applications in a pulse capacitor charge power supply (CCPS). Since there are no brushes, the brushless doubly-fed alternator is expected to have high reliability and long service life. The excitation winding of the BDFA that is placed in the stator slots can be supplied with either dc or ac. In previous studies, regardless of the rotor configuration, the natural speed of BDFA is 60 f/(p 1 + p 2 ), i.e., based on the additive mode. To increase the alternator's natural speed, expand the alternator's operation as well as control range and to promote the alternator's power density, this paper presents the differential mode, i.e., natural speed is equal to 60 f/ρ 1 - ρ 2 |. The author will introduce the detailed design method of the BDFA based on the differential mode. Utilizing the finite-element model of the alternator, we will analyze the magnetic field distribution and calculate inductance parameters of the BDFA. Subsequently, the inductance mathematic model of the BDFA will be established. We also establish the simulation model of the pulse CCPS. Finally, we will verify the feasibility of the design scheme for the BDFA through the simulation results in a pulse CCPS system.

As a novel pulsed-power supply, the air-core pulsed alternator is outstanding in providing repetitive pulse with high energy density, and preferred in a variety of fields including laser and electromagnetic launch, etc. To achieve a superior field excitation power supply, the air-core pulsed alternator usually adopts a self-excitation module, putting some emphasis on the design of the excitation conditions. In previous studies, the commutation voltage drop is neglected in excitation condition analysis. However, the voltage drop may have some significant impacts on the excitation conditions, and the neglect would cause a deviation between analysis and practices. This paper focuses on the analysis of excitation condition, taking the commutation voltage drop into account.

The air-core pulsed alternator has been studied for more than three decades. However, its optimized design theories are still rarely reported. The performance of the air-core pulsed alternator-based pulsed-power system is often closely associated with the electrical machine parameters, the system structure, and the load requirements. The parametric optimization of this type of alternator has a very important influence on the performance. This paper focuses on the optimization theory of the air-core pulsed alternator design, including the optimization of the magnetic field distribution, the turn number of armature winding, and the turn number of field winding. The features of the magnetic field distribution in the air-core pulsed alternators are analyzed based on the analytical expressions. By designing a ferromagnetic shield put on the outside of the stator, the radial magnetic field component increases and the circumferential one decreases. The optimization principles of the winding turn numbers are also deduced based on the system circuit and operation mode. The optimization theories are verified by system-level dynamic simulation. Finally, some rules are summarized, which are beneficial to the optimized design of the air-core pulsed alternator.

In pulsed power supply for electromagnetic launchers, air-core pulsed alternators have obvious advantages to enhance the power density and energy density. Compared with conventional machines, the large excitation currents are required to establish the high flux densities needed in the air-core magnetic circuits, so the self-excitation mode is adopted in these systems. Therefore, we make great efforts on the conditions of self-excitation mode. This paper presents a detailed description about the transient process of the air-core pulsed alternator operating at self-excitation mode. First, it's necessary to supply a seed current rapidly prompting the alternator running at self-excitation mode. So the capacitance and pre-charged voltage on the capacitor in excitation initialization module determining the seed current is analyzed, a reasonable value range of the capacitance and the voltage can be decided. Then, when the machine is in self-excitation mode, a detailed study about the current and the voltage through the excitation winding and the armature winding are developed. Also some new concepts, such as ‘R feq ’ meaning the equivalent impedance of the excitation winding and ‘K fi ’ applied to evaluate the growth rate of the excitation current, are proposed to simplify the transient analysis. They also play a guiding role to improve our systems. Finally, the results of the SABER simulation are presented to validate our analysis.

A novel 4/4 stator/rotor single-phase doubly salient permanent magnet machine (DSPMM) with asymmetric stator poles is proposed in this paper. The stator poles of proposed machine are distributed non-uniformly along the circumference of the stator yoke. Firstly, it investigates the new topology and operation principle based on diagram description and mathematical derivation. Then, the dimension equation, equivalent magnetic circuit model and current expression are derived and verified based on two-dimension finite element analysis (2-D FEA) in details. Finally, full comparison on electromagnetic performance indexes of the new machine with those of a traditional one is also presented. It indicates that the proposed novel structure has much higher torque density, lower losses and higher efficiency than those of the traditional one under the same volume, electrical load, etc.

The investigation of inductance mathematic model of a homopolar inductor alternator (HIA) in a novel pulse-capacitor charge power supply (CCPS) is presented. We study the characteristics of the inductance parameters based on the HIA theory and 3-D finite element analysis, establish the inductance mathematics model of HIA, and build a novel pulse-CCPS with 12/10-pole HIA. We also establish the simulation model of the power supply and compare the simulation results with the experimental one. The results prove the correctness of the inductance mathematic model. Finally, the problem of parameters-matching between the charging circuit and the HIA inductance is discussed.

Air-core pulsed alternators greatly enhance the power density capabilities of pulsed power supply for electromagnetic launchers. Compared with iron-core electric machines, they require very high-excitation currents. Usually, the self-excitation mode is adopted in these systems. However, the self-excitation mode is a positive feedback process that should be precisely controlled to avoid the system being destroyed. The excitation losses are very large during the process of establishing the large field current. To solve these problems, a new excitation mode, the pulse-excitation mode, is presented in this paper. The main idea is that a pulsed current charges the field coil so that the field coil and the armature coil conduct only for a short time around the main discharge pulse. This will avoid the machine being overheated and the risk of positive feedback process. Compared with the self-excitation mode, the pulsed alternator can be operated in a higher discharge frequency and the circuit schematic of the system is simpler. A larger field capacitor is used that charges the field coil to the desired current just by a pulse. As the energy density of pulse capacitor is enhanced rapidly, the volume and mass of the field capacitor are acceptable. The pulse-excitation mode is a combination of pulsed alternator and pulsed capacitor. In this paper, the characteristics of self-excitation and pulse-excitation are analyzed, respectively. The performances of both systems are simulated, and the main waveforms are presented. Finally, there is a practical comparison between them.

This paper presents a nontraditional power supply system for lasers in which an active compensated pulsed alternator (ACPA) drives the flashlamp load directly instead of the capacitor groups. However, the delivered power and pulsed width of the ACPA are two pivotal machine output parameters, which are determined by the flashlamp load. In other words, the characteristics of the flashlamp load must be elaborately considered during the design process of ACPA. In this paper, the structure of a new single-phase iron-core nonsalient pole ACPA is proposed, which couples the flashlamp load. The theory and advantages of ACPA are also introduced. The characteristics of the transient magnetic field distributions are calculated by finite-element analysis to verify the electromagnetic programming design of ACPA. A circuit model of the power supply system is then established to simulate the performance. Some simulation waveforms are obtained and explained.

One novel 4/6 stator/rotor single phase doubly salient permanent magnet machine with asymmetric stator poles is proposed in this paper. Design optimization technique based on 2D finite element analysis (FEA) is used to refine the proposed machine. Besides, comparison of electromagnetic performance indexes of the proposed machine with that of traditional 4/6 stator/rotor single phase doubly salient permanent magnet machine with uniformly distributed stator poles is also presented. It indicates that the proposed machine has much higher torque, lower core losses, and higher efficiency than those of traditional one.

In this paper, a 15kW novel out rotor flux switching permanent magnet machine (OR-FSPM) with 48/56 stator/rotor configuration (OR-FSPM) is proposed for in-wheel electrical vehicle. The OR-FSPM machine with fractional-slot concentrated windings (FSCWs) has become good candidates for in-wheel motors due to their robust rotor structure, high torque and power capability. What is more, the out rotor configuration of the machine can provide the convenient for in-wheel direct drive. Comprehensive simulations based finite element analysis (FEA) are studied on the overall electromagnetic property of this machine, especially the output capability.

An air-core pulsed alternator is made of nonferromagnetic materials, which needs very high field current. Self-excitation is usually applied in these systems. This is a positive-feedback progress, which takes tens of milliseconds to reach the desired large field current. The field loss is one of the main limitations of the machine design. This paper presents a new excitation mode, which is the pulse-excitation mode. The main idea is that a pulsed current charges the field coil so that the field coil and the armature coil conduct electricity only for a short time around the main discharge pulse. The field-current pulse is supplied by a pulse capacitor. Generally speaking, the pulse-excitation mode is a combination of pulsed alternator and capacitor. Compared with the self-excitation operation mode, the pulse-excitation operation mode reduces the field loss in each discharge process. This increases the discharge frequency of the air-core alternator pulse-power system. In addition, the repeat discharge-current pulses could have similar peak value. In this paper, the pulse-excitation mode in a pulsed-alternator system is investigated. The simulation results of this scheme are presented. The discharge current, field current, voltage of the field capacitor, and rotational-speed changes are analyzed. Finally, the advantages and disadvantages of this mode are discussed.

This paper presents the investigation of a novel capacitor-charging power supply through inertial energy storage of a homopolar inductor alternator (HIA). The structure of a new 18/16-pole HIA is proposed, and we introduce the theory and advantages of HIA. The characteristics of the static magnetic field distributions are calculated by finite-element analysis, and a basic mathematic model of HIA is set up. We propose an efficient and stable capacitor-charging circuit topology to meet the requirements of this system. A functional model of the key device, namely, IGCT, is also established. Finally, we verify its feasibility and advantages through analysis of the system simulation.

The air-core pulsed alternator has advantages in the application of pulsed power region, such as in electromagnetic launchers. The self-excitation and discharge processes in an air-core alternator are more complicated than traditional iron-core generators. In this paper, a mathematical model of an air-core pulsed alternator is built and several critical problems are analyzed, such as the conditions for successful self-excitation, the time needed for self-excitation, the waveforms of electromagnetic torque, discharge current and load voltage, and the compensation action during discharge, the effect of triggered angles, the rotational speed curve, and the energy reclaiming. Investigation of self-excitation and discharge processes in an air-core pulsed alternator is helpful for understanding the operation principle, predicting the performance, and analyzing and designing the system.

Multiphase Air-Core Pulsed Alternators have been studied for almost two decades. However, its design and optimization theories are still rarely reported. The main parameters of this type of alternators have very important influence on the performance. These parameters are often closely associated with system performance parameters, the system structure and the load requirements. This paper begins with describing the basic design theory of the GW-scale air-core pulsed alternator. Then, the relationships of major parameters are analyzed, including the main dimensions, the magnetic field, the armature turns in series per phase, the number of turns per pole of the field winding, the load parameters and etc. Finally, the optimization theories are verified by system-level dynamic simulation.

In this paper, the d- and q-axis synchronous reactances of homopolar inductor alternator (HIA) are calculated. First, an approximate 2D model of HIA is developed and its relative air-gap permeance function is described. The harmonic amplitudes of the per-unit quantity of relative air-gap permeance function are determined by 2D finite element analysis (FEA). Then, the analytical expressions for the synchronous reactances in the direct-axis (d-axis) and quadrature-axis (q-axis) are derived from magnetomotive force (MMF)-relative air-gap permeance function theory, including armature reaction reactance and armature leakage reactance. Finally, theoretical results are compared with the simulation and experimental results.

This paper presents a new type Brushless Doubly-fed Alternator (BDFA) based on the differential mode and conducts research on its application in a pulse Capacitor Charge Power Supply (CCPS). Because there are no brushes, the Brushless Doubly-fed Alternator will have high reliability and long service life. The excitation winding of the BDFA which is set on stator can be supplied with either Direct Current or Alternating Current. In previous studies, regardless of the rotor configuration, the natural speed of BDFA is 60f / (p1+ p2), i.e. based on the additive mode. In order to increase the alternator's natural speed, expand the operating and control range and promote the alternator's power density, this paper presents the differential mode, i.e. its natural speed is 60f /|p1-p2|. We will introduce the detailed design method of BDFA based on the differential mode. Utilizing the finite element model of the alternator, we will analyze the magnetic field distribution and calculate inductance parameters of the BDFA, and then the inductance mathematic model of the BDFA will be established. We also establish the simulation model of the pulse CCPS. Finally, we will verify the feasibility of design scheme for the BDFA through the simulation results in a pulse CCPS system. Index Terms: Brushless Doubly-Fed Alternator (BDFA); Differential Mode; Finite Element; Capacitor Charge Power Supply (CCPS).

This letter aims to settle the controversy about whether or not the two-reaction theory is applicable to homopolar inductor alternator (HIA). First, the prerequisite of two-reaction theory is introduced. The direct and quadrature axes of HIA are defined and the corresponding armature reaction fields are calculated respectively based on finite element method. A conclusion that two-reaction theory is applicable to HIA is made using spatial overlay analysis.

This paper presents the investigation of inductance mathematic model of Homopolar Inductor Alternator (HIA) in a novel pulse capacitor charge power supply. We study the characteristics of the inductance parameters based on the HIA theory and three-dimensional finite element analysis, establish the inductance mathematics model of HIA, and build a novel pulse capacitor charge power supply with 12/10-pole HIA. We also establish the simulation model of the power supply and compare the simulation results with the experimental. The results prove the correctness of the inductance mathematic model. Finally, the problem of parameters-matching between charging circuit and the HIA inductance is discussed.