Homopolar Inductor Alternator Research Articles

Investigation of Magnetic Effect in High-Speed Homopolar Inductor Alternator

Investigation of Magnetic Effect in High-Speed Homopolar Inductor Alternator

Analysis and Experiment of Homopolar Inductor Alternator With an Active Compensated Winding in Capacitor Charging Power Supply System

Analysis and Experiment of Homopolar Inductor Alternator With an Active Compensated Winding in Capacitor Charging Power Supply System

Research on Homopolar Inductor Alternator With a Short-Circuit Compensated Winding in CCPS System

Research on Homopolar Inductor Alternator With a Short-Circuit Compensated Winding in CCPS System

An Optimized Design Method of Homopolar Inductor Alternator Based on Genetic Algorithm

Homopolar inductor alternator (HIA) plays an important role in capacitor charging power supply (CCPS) system. Due to the 3-D-structure magnetic circuit and short-circuit working condition, the design method of HIA is different from that of conventional machines obviously. On the current research, the traditional design method is usually adopted, that is the alternator is designed depending on experience at first, and then, the charging performance is verified by system simulations. This method could cause HIA’s performance to be much higher than the system’s requirement, resulting in energy wasting, in addition, too big system is not suitable for some size-limited situations, such as on-board, ship-borne, and other mobile supply. In this article, a new optimization design method of HIA is proposed. An “optimal function” is derived first, which can find out the “optimal charging power point” under the charging requirements. Then, genetic algorithm (GA) is applied to investigate the HIA with smaller volume and lighter mass. Finally, in order to verify the optimization method, the characteristics of the optimal HIA are carried out by finite element method and system simulation. The results demonstrate that the designed HIA can well meet the charging requirements, and its performance is better than the HIA designed by the traditional method obviously. Meanwhile, the proposed design method has significant advantage to design smaller and lighter alternators, which is important to improve the output performance and mobility of HIA-CCPS.

Optimization of Design Method and Experiment of A Repetition Pulse Charging HIA-CCPS

Due to the advantage of high-power density, high energy storage density and fast repetition pulse charging ability, homopolar inductor alternator (HIA) has been successfully applied in the capacitor charging power supply (CCPS) system, leading to a new capacitor charging power supply (HIA-CCPS) in recent years. To obtain a compact HIA-CCPS with high performances of light weight, small size, high repetition pulse output ability and so on, it is still of great necessity to develop quantitative analysis from alternators to the pulse load such as capacitors. Unfortunately, many researchers only focus on the alternator design or use a single charging process with constant speed instead of the repetition charging dynamic process with a large speed change for simplifying analysis. As a result, parameters' influence between alternators and others in the system is not clear, it is not easy to find out a system-wide optimal scheme. In this text, a comprehensive design method for HIA-CCPS with repetition pulse charging is proposed. Firstly, a simplified model is presented to analyze the influence of different parameters. The repetition pulse charging characteristics of HIA is investigated. After that, a novel design method of repetition pulse charging is given, and an excitation control strategy during the charging is put forward to ensure the charging time remains almost constant between each charging time. Finally, a platform of HIA-CCPS is developed and experiments are carried out. The experiment results indicate that the proposed method is very helpful for a repetition charging HIA-CCPS to develop the optimization design.

Study of capacitor charge power supply with homopolar inductor alternator: System modelling and mode analysis

Capacitor charge power supply (CCPS) based on homopolar inductor alternator (HIA) has been successfully used in capacitor-based pulsed power supply (PPS), but there is still no perfect system modelling and compete system parameter design method. In this study, the system modelling and mode analysis of HIA-CCPS is developed in detail. First, a simplified CCPS model is proposed based on the voltage-behind-reactance (VBR) model of HIA and the phase base-value system (PBVS). Second, four different modes of CCPS are derived on conditions of the constant voltage load (CVL) assumption; the symbols and terms in these modes are unified. The equations derived in this study are the basis of the system parameter design and the further research of HIA-CCPS.

Analysis of a Novel Excitation Compensated Homopolar Inductor Alternator Used for Capacitor Charge Power Supply

For improving the power density of a homopolar inductor alternator (HIA) in a capacitor charge power supply (CCPS), a novel excitation compensation (EC) method is proposed in this article, wherein a compensation winding is installed in the HIA for providing pulse excitation and increasing the charge power. First, high-power and high-energy density requirements of the CCPS in the pulsed power supply (PPS) are presented, and the power density problem of the HIA caused by its homopolar structure is discussed. Second, methods for improving the charge power in the CCPS are studied, and a good way is to provide strong excitation to increase the machine electromotive force (EMF) during the charge process, whose difficulties are also studied. Third, a novel excitation-compensated HIA (ECHIA) is introduced and the principle and the effect of different EC circuits are analyzed. In the end, simulation results of the same size ECHIA and a conventional HIA show that the novel EC method can indeed improve the charge power in the CCPS and help the HIA achieve higher power density.

Study of a Novel High-Speed Compensated Pulsed Alternator With Multistage Stator Cores

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.

A Novel Critical Analysis Method of Homopolar Inductor Alternator for Preliminary Design in Capacitor Charge Power Supply

In order to realize quick preliminary design for capacitor charge power supply (CCPS), a novel critical analysis method of homopolar inductor alternator (HIA) is proposed in this paper. First, a specific base value system of CCPS is proposed for making the critical analysis method universally applied for different machine and charge parameters. Second, under the equivalent average-value phase model of HIA, a critical curve and a maximum power analysis method based on the curve are proposed. After that, an outline of the preliminary machine design under the critical analysis method is presented. Third, considering the salient rotor structure of HIA, under the equivalent average-value direct- and quadrature-axis (DQ) model of HIA, a critical map as well as its maximum power analysis method is proposed. In the end, for these two types of critical analysis method under different average-value models, each of their advantages and applications are discussed.

Design Consideration of Eddy-Current Loss for Rotor of HIA With Rectifier and Capacitive Loads

Homopolar inductor alternator (HIA) with rectifier and capacitive loads is a promising choice for pulsed power supply. The solid-iron rotor of HIA can rotate at a very high speed, but this causes serious eddy-current loss in the rotor and results in local overheating on rotor face. In this paper, the analytical method was used to calculate the rotor eddy-current loss for HIA with rectifier and capacitive loads, and the effect of eddy-current shielding on the rotor eddy-current loss was also discussed. The analytical results are coincided with the results simulated by a simplified 2-D field-circuit coupled simulation. This paper shows that in order to reduce the rotor eddy-current loss, the air-gap length and the pole number should be as large as possible and the windings should be distributed and short-pitch. Meanwhile, an important conclusion is that the eddy-current shielding cannot decrease the eddy-current loss for HIA with rectifier and capacitive loads; on the contrary, it increases the eddy-current loss, compared to the case with the rectifier and resistive load.

Investigation of a Two-Dimensional Analytical Model of the Homopolar Inductor Alternator

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 Control Strategy and Experiment Research of Integrated Energy Storage Pulsed Alternator

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.

Research on the No-Load Rotor Eddy Loss of a High-Speed Pulsed Alternator

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.

Analytical Calculation of Synchronous Reactances of Homopolar Inductor Alternator

In this paper, the direct-axis (d-axis) and quadrature-axis (q-axis) synchronous reactances of homopolar inductor alternator (HIA) are calculated. First, an approximate 2-D model of HIA is developed and its relative air-gap permeance function is described. Then, the analytical expressions for the synchronous reactances in the d-axis and q-axis are derived from magnetomotive force-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.

Analysis of Air-Gap Magnetic Field in Homopolar Inductor Alternator by Analytical Method and FEM

This paper investigates the air-gap magnetic field characteristics of homopolar inductor alternator (HIA), including theoretical analysis, numerical calculation, and experiment. First, the structure and magnetic circuit characteristics of HIA are analyzed. Second, a linear model of distributed magnetic circuit of HIA is established. An analytical formula for calculating the main air-gap magnetic field at different axial positions is deduced and obtained. Third, finite element method (FEM) is used to compute the magnetic field of HIA. The results from FEM are nearly consistent with those from analytical method. Finally, a prototype is constructed to verify the theoretical analysis and numerical computation. The research shows that the distribution of the main air-gap magnetic field of HIA is uneven along the axial direction. The proposed analytical formula contributes to calculate the main air-gap magnetic flux density of HIA.

Repetition pulse charging characteristics for homopolar inductor alternator with rectified capacitive load

This paper presents the single pulse charging characteristics of a homopolar inductor alternator (HIA) with rectified capacitive load, and analyzes the relationship between HIA's voltage, HIA's frequency, charging voltage, and charging time. The process of energy conversion in the whole system and the proposed reasonable excitation current control method are also discussed. Experiments are carried out based on theoretical analysis and simulation. Both simulation and experimental results prove the validity and feasibility of the theoretical analysis and the excitation current control. We also prove the feasibility of high‐power and repetition pulse charging supply based on rotating storage. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Performance of Homopolar Inductor Alternator With Diode-Bridge Rectifier and Capacitive Load

This paper presents the performance of homopolar inductor alternator (HIA) with diode-bridge rectifier and capacitive load. According to the conduction and commutation rules, all the operational modes included in the bridge rectified capacitive load are considered. A simplified average-value mathematical model is established; furthermore, we derive the load characteristic under every operation mode. Using the fundamental machine differential equations and the connecting characteristics between alternator and rectifier, we establish a port-network state model of the system. The performance of the HIA with bridge rectifier and capacitive load can be predicted from charging current, commutating angle, and given parameters of the alternator. Theoretical results are compared with the simulation results obtained from numerical procedure.

Inductance Mathematic Model of a Homopolar Inductor Alternator in a Novel Pulse Capacitor Charge Power Supply

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.

Calculation and Analysis of Iron Loss in Homopolar Inductor Alternator

DC-biased magnetic induction can occur in homopolar inductor alternator (HIA). In this paper, an experimental method is introduced and the corresponding experimental platform is constructed to measure the magnetic loss characteristics of magnetic material under DC-biased magnetic induction. The curves of the magnetic loss under DC-biased magnetic induction are obtained. The magnetic loss of HIA under DC-biased magnetic induction is calculated. The influence of the structure parameter and excitation current on the stator core loss is investigated. Some significant conclusions include: the magnetic material suffers an increase in magnetic loss under DC-biased magnetic induction relative to sinusoidal induction; the magnetic loss of HIA, which is quite different from the loss of conventional electrical machine under sinusoidal induction, is almost proportional to the operating speed; the stator core loss of HIA achieves to the maximum value when the coefficient of the rotor tooth width is approximate to 0.5.

Analysis of brushless DC generator incorporating an axial field coil

This paper describes the magnetic analysis and experiment of a three-phase field assisted brushless DC (BLDC) generator. Unlike conventional BLDC generators, the permanent magnet is replaced with an assisted field winding. The stator and rotor are constructed with two dependent magnetically sets, in which each stator set includes nine salient poles with coil windings, and the rotor comprises of six salient poles. Other pole combinations also are possible. This construction is similar to a homopolar inductor alternator. The DC current in the assisted field winding produces axial flux which makes the rotor magnetically polarized at its ends. The magnetic field flows axially through the rotor shaft and closes through the stator teeth and the machine housing. To evaluate the generator performance, two types of analysis, namely the numerical technique and the experimental study have been utilized. In the numerical analysis, 2-D finite element (FE) analysis has been carried out using a MagNet CAD package (Infolytica Corporation Ltd.), to confirm the accuracy of the predicted flux-linkage characteristics, whereas in the experimental study, a prototype BLDC generator was constructed for verifying the actual performance. Furthermore, the evaluation method based on a hybrid numerical method coupling the finite element (FE) analysis and boundary element (BE) method, has been carried out to confirm the accuracy of the 2-D FE analysis simulation results. It provides not only confirmations of the investigation in results but also exact illustration for magnetic field distribution for this complex generator geometry.