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In previous studies, the field winding of the brushless pulsed alternator (BPA) is embedded in the stator slots, which is supplied by dc power or variable frequency power. The advantage is that the field current can be independently adjusted. It means that the BPA system needs a standalone excitation system, which will increase the volume and cost of the system. If we substitute electric excitation for permanent magnet excitation, not only the volume and cost of the BPA system can be decreased but the efficiency and flexibility can be enhanced. In this paper, the design schemes for electric excitation and permanent magnet excitation BPA are presented. For comparison, the stator and rotor dimensions of the two kinds of BPA are both the same. The characteristics of electric excitation and permanent magnet excitation BPA are analyzed by the finite-element method and field-circuit coupling method. Finally, the BPA systems with a resistive load are established, the performances of both the two excitation modes are compared. According to the simulation results, we conclude their advantages and disadvantages. [ABSTRACT FROM AUTHOR]

This paper describes a tubular linear motor with special permanent magnet. Then, two kinds of permanent magnet magnetization directions for this motor are proposed, and the air-gap magnetic field is calculated and researched based on a finite-element method. Moreover, the magnetic field of the slotless tubular linear motor is contrasted with that of the traditional interior axially magnetized permanent magnet tubular linear motors. Finally, the advantages of the motor are analyzed and pointed out. [ABSTRACT FROM AUTHOR]

The six-phase transverse flux tubular permanent magnet linear motor (PMLM) has many advantages compared with conventional linear motors. However, the reliability of its drive system can still be influenced by power converter or machine faults. This paper presents a fault-tolerant control strategy for six-phase transverse flux tubular PMLM based on synthetic vector method when the machine has a single-phase open-circuit fault. The operation of six-phase transverse flux tubular PMLM is described as well as its basic mathematical model. Then, the principles of synthetic vector method are introduced. Based on these theories, the fault-tolerant control strategy is derived in detail under the single-phase open-fault condition. In addition, a fault-tolerant dual three-phase four-leg inverter’s drive topology that can be applied under this faulted condition is proposed. Moreover, to implement the control algorithms proposed, a modified space vector modulation is presented. Both the finite-element simulation and MATLAB/Simulink simulation results illustrate the validity of the proposed fault-tolerant control as well as the associated control topology and space vector modulation. [ABSTRACT FROM PUBLISHER]

In this paper, a stair-step-shaped magnetic pole structure is proposed to use in a permanent-magnet linear synchronous motor (PMLSM) for its application in an electromagnetic launch system. The aim of this configuration is to shape the air-gap flux density distribution produced by poles to be as close to a sine waveform as possible for the reduction of thrust ripple and the increase of motor controllability. An analytical model is derived for the PMLSMs by solving Maxwell equations and applying the superposition theorem for calculating the magnetic field, electromotive force, and thrust/torque of the motor. Magnet dimensions are then optimized using the analytical method and genetic algorithm, where the reduction of air-gap flux density harmonics is considered as the optimization target. Finally, the effectiveness of the proposed technique to enhance the motor performance is investigated by a time-stepping transient finite-element method. The results show an improvement in the optimal motor performance. [ABSTRACT FROM PUBLISHER]

Since permanent magnet linear synchronous motor (PMLSM) has a bright future in electromagnetic launch (EML), moving-magnet PMLSM with multisegment primary is a potential choice. To overcome the end effect in the junctions of armature units, three different ring windings are proposed for the multisegment primary of PMLSM: slotted ring windings, slotless ring windings, and quasi-sinusoidal ring windings. They are designed for various demands of EML, regarding the load levels and force fluctuations. Auxiliary iron yokes are designed to reduce the mover weights, and also help restrain the end effect. PMLSM with slotted ring windings has a higher thrust for heavy load EML. PMLSM with slotless ring windings eliminates the cogging effect, while PMLSM with quasi-sinusoidal ring windings has very low thrust ripple; they aim to launch the light aircraft and run smooth. Structure designs of these motors are introduced; motor models and parameter optimizations are accomplished by finite-element method (FEM). Then, performance advantages of the proposed motors are investigated by comparisons of common PMLSMs. At last, the prototypes are manufactured and tested to validate the feasibilities of ring winding motors with auxiliary iron yokes. The results prove that the proposed motors can effectively satisfy the requirements of EML. [ABSTRACT FROM PUBLISHER]

In this paper, a magnetic analysis of large linear motors with long primary and short interior permanent magnet (PM) secondary is presented. The calculations are carried out using a finite-element method, taking into account the secondary motion and saturation in iron parts. Reluctance force could be increased using interior PM secondary. The thrust force oscillations are evaluated to obtain minimum force ripple. Furthermore, a magnet demagnetization analysis is presented to evaluate the magnet demagnetization risk under loading. Reduction in the magnet volume is considered for cheaper and simpler secondary structure. [ABSTRACT FROM AUTHOR]

Some intriguing advantages of permanent-magnet linear synchronous machines (PMLSMs), such as simple structure, high thrust, high efficiency, ease of maintenance, and controller feedback, make it possible to take the place of steam catapults in the future. The conventional PMLSM is renowned for its simple structure and high efficiency, whereby the high reactive power resulted from great leakage inductances during the long stator. Thus, great concern is paid to the section structure of the PMLSM. A sectioned permanent-magnet linear synchronous machine (SPMLSM) used in the EMALS is introduced in this paper, whose stator core is continuous but the armature winding is divided into two sectioned parts. First, the electromagnetic fields of the SPMLSM are investigated analytically. Then, the fields are computed by the finite-element method (FEM) and measured experimentally. Not only are the self-inductances and mutual inductances in one section studied but also the mutual inductances between the two sections. These inductances are then calculated by the FEM and measured experimentally. Good correlation among the results was obtained by these three methods. [ABSTRACT FROM AUTHOR]

This paper investigates a linear electromagnetic launcher with tubular transverse flux permanent-magnet linear machine (TFPMLM). Special focus is given on its cogging force characteristic, including the theoretical analysis and computer-aided simulation. Both 3-D and equivalent 2-D finite-element analyses are performed to calculate the cogging force, and the results are compared. It is shown that the proposed 3-D to 2-D equivalence can predict the cogging force of the tubular TFPMLM in an accurate and fast way. [ABSTRACT FROM AUTHOR]

Magnetic flux distributions of the permanent magnet (PM) section and the homopolar induction (HI) section in a hybrid excitation synchronous generator (HESG) are calculated by using the finite element method (FEM). The influences of the axial-length ratio of the two sections on the back EMF, inductance, and terminal characteristics of the PM section, the HI section, and the HESG are analyzed. The prototype experiments have verified the validity of the calculation and analysis processes. The studies on the HI section have shown the following: 1) The operating air-gap flux distribution along the axial direction is uneven; 2) there is an approximate linear relationship between the radial component average of the operating air-gap flux density and the axial length; 3) a quadratic relationship between the back EMF and the axial length exists; and 4) it is necessary to compute and optimize the axial-length ratio of the PM section and HI section to increase the output voltage and improve the terminal characteristics of the HESG. [ABSTRACT FROM AUTHOR]