Permanent Magnet Excitation Research Articles

Performance Analysis of Synchronous Reluctance Machines Having Nonoverlapping Concentrated Winding and Sinusoidal Bipolar With DC Bias Excitation

This paper describes the operation principle and analyzes the electromagnetic performance of synchronous reluctance (SynR) machines having the structure of switched reluctance machines but excited by an ac sinusoidal current with dc bias, i.e., salient-pole SynR with nonoverlapping concentrated windings and a dc bias excitation. Under such excitation, these machines become similar to permanent magnet (PM) counterparts. The dc bias, which is equivalent to the PM excitation, produces back electromotive force (EMF) in the ac coils as well as cogging torque. Thus, injecting the ac coils by sinusoidal currents results in output torque on the machine shaft. The produced back EMF and cogging torque, and torque ripple magnitudes and periods, as well as the optimal ac current angle and the ac/dc current density ratio, strongly depend on the winding connection configuration. The maximum average torque can be achieved when the ac/dc current density ratio is 2 and the symmetrical winding connection, which results in a lower torque ripple, is employed. A prototype machine is built and tested to confirm the analyses and conclusions.

Research on new hybrid excitation PM synchronous generators with tooth harmonic excitation

Purpose – In order to keep the advantages of PM generators and eliminate its disadvantage – difficulty in regulating the magnetic field, hybrid excitation is an effective way. The purpose of this paper is to propose a novel way to achieve hybrid excitation by use of tooth harmonic field. Design/methodology/approach – Unlike weakening the tooth harmonics field and EMF in traditional machines, in this paper the tooth harmonics field is proposed to form a novel hybrid excitation permanent magnet synchronous generator (HEPMSG). Findings – The generation mechanism of tooth harmonic electromotive force (EMF) of rotor winding is introduced, and its influencing factors are discussed in detail. The matching design of tooth harmonic winding and field winding for maximum output field current of tooth harmonic excitation system is analyzed. Practical implications – This machine can achieve not only effective adjustment of the air-gap magnetic field, but also elimination of the brushes and slip rings. Originality/value – Unlike weakening the tooth harmonics field and EMF in traditional machines, in this paper the tooth harmonics filed is proposed to form a novel hybrid excitation PM synchronous generator. This machine can achieve not only effective adjustment of the air-gap magnetic field, but also elimination of the brushes and slip rings.

Electrical Design Considerations for a Bearingless Axial-Force/Torque Motor

A axial-force/torque motor (AFTM) establishes a completely new bearingless drive concept. The presented Lorentz-force-type actuator features a compact and integrated design using a very specific permanent-magnet excitation system and a concentric nonoverlapping air-gap stator winding. The end windings of the bent air-core coils, which are shaped in a circumferential rotor direction, provide active axial suspension forces. Thus, no additional (bearing) coils are needed for stable axial levitation. The four remaining degrees of freedom of the rotor are stabilized by passive magnetic ring bearings. This paper concentrates on the determination of the lumped parameters for the dynamic system modeling of the AFTM. After introducing a coordinate transformation for the decoupling of the control variables, the axial suspension force, and the drive torque, the relations for coil dimensioning are developed, followed by a discussion of the coil turn number selection process. Active levitation forces and drive torque specifications both must be concurrently fulfilled at a nominal rotor speed with only one common winding system, respecting several electrical, thermal, and mechanical boundaries likewise. Provided that the stator winding topology is designed properly, a simple closed-loop control strategy permits the autonomous manipulation of both control variables. A short presentation of the first experimental setup highlights the possible fields of application for the compact drive concept.

Mathematical modeling of electromechanical processes in a brushless DC motor

On the basis of initial assumptions, a mathematical model that describes electromechanical processes in a brushless DC electric motor with a salient-pole stator and permanent-magnet excitation is created.

Modeling and Testing of an Armature-Reaction-Compensated (PM) Synchronous Generator

Hybrid excitation synchronous generators are a special class of electrical machines in which the total rotor current linkage is produced by the simultaneous action of two different excitation sources: permanent-magnet (PM) excitation and field winding excitation. In the island operation, there is a need to compensate the armature reaction to keep the generator terminal voltage constant. The permanent magnet excitation is used to create the no-load excitation to the generator and the rotor winding is used as an armature reaction compensating winding. This paper studies the applicability of an armature-reaction-compensated PM synchronous generator to a marine diesel genset. This paper presents an analytical approach for the electromagnetic design of the proposed topology. Finite-element analysis and experimental measurements are performed to verify the results of the analytical approach.

Design of a New Frog-Leg Winding Permanent-Magnet Brushless DC Motor

A new frog-leg winding permanent-magnet (PM) brushless DC motor is proposed in this paper. Besides PM excitation and electric commutation, the motor has a type of mesh winding inherited from the conventional brushed DC motor. With the aid of a position sensor, the new motors operation principle is basically as same as the brushed one. Based on the frog-leg winding configuration of simplex lap and duplex wave, the motor is designed with 4 poles and 22 slots, and the number of phases is set as 11. Furthermore, an exact analytical method for predicting the instantaneous magnetic field, electromotive force (EMF) induced in the armature winding, cogging torque and output torque of the new motor is introduced. Results from this analytical method are compatible with corresponding finite element analyses (FEA).

Effects of Permanent Magnet Excitation on Material Removal Rate in Area Taking Magnetorhelogical Finishing

In this paper, a novel area taking MRF process using permanent magnet as excitation was proposed. Four types of permanent magnet configurations were considered. Polishing experiment was conducted. Effects of different permanent magnet configurations on material removal rate (MRR) were discussed.

Sliding Mode Controller based Permanent Magnet Synchronous Generator with Z-Source Inverter for Variable Speed Wind Energy Translation Structure using Power Quality Enhancement

scale stand alone wind generators are a significant different source of electrical energy. Unluckily, most of these systems do not capture more power at every wind speed. Particularly, at low wind speeds which are provide low power. To address this problem, this paper has been proposed a permanent magnet synchronous generator (PMSG) and Z- source inverter. This generator is connected to the power network by means of a Z-source inverter. Permanent-magnet synchronous generators are having some amazing characteristics such as with a reduction of burden and level, advanced performance, minimized size of gear box and no need of external power in permanent magnet excitation. The PMSG defeat the all other generators, marvelous performances without absorb the grid power.This paper presents a Z-source inverter that can be proposed as an option power conversion concept for variable speed wind turbines. It consist both buck and boost capabilities as they permit the inverter to perform the shoot through state. It utilizes a special Z-source network (L-C network) to DC-link in between inverter and the DC source. By controlling the shoot-through duty cycle of IGBTs in inverter system, we can diminish the line harmonics, develop power factor, and enlarge output voltage range.

Magnetic field enhanced photoelectrochemical response of a nanostructured titanium dioxide anode

The concept of permanent-magnet photoelectrochemical fuel cell is proposed. The fuel cell contains a TiO2 nanotube anode and a platinum cathode. Water was used as the fuel. The anode has a self-organized high aspect ratio TiO2 nanotube layer made through electrochemical oxidation of Ti. Photocatalysis and permanent magnetic field excitation experiments were performed. The photoelectrochemical responses of the anode to visible (Vis) and ultraviolet (UV) light were studied to examine the magnetic field effect. The open circuit voltages were 0.0564, 0.1625, 0.1898 and 0.376V, under the excitation of Vis, UV, magnet and magnet+UV, respectively. Current density was measured under different linear potential scanning conditions. It reached a value of 5.23mA/m2 just under the excitation of the permanent magnet at a bias voltage of 2V. Combining the magnetic action and the photovoltaic effect, the titanium dioxide photosensitive anode showed a maximum photocurrent density of 296.05mA/m2 at 2V bias. It is concluded that the absolute value of open circuit voltage (OCV) of the fuel cell due to the exposure to the magnet field is much higher than that due to either UV or Vis light illumination. However, UV light excitation results in higher current density in the measurement.

Impact of windings switching on torque‐speed curves of PM BLDC motor

PurposeWhen phase windings of brushless DC motor are switched, additional voltage drops across inductances of main circuit appear. These drops lead to, among other effects, increase of torque‐speed curve slope. The discussed research has been aimed at working out a simple and precise method of identifying torque‐speed characteristic of PM BLDC motor. The elaborated method takes into account the influence of windings switching and motor inductances on motor torque‐speed characteristic. In order to assess the results, extensive test simulations of models implemented in Matlab/Simulink software have been run. Results of analysis and test simulations have been compared with lab test results of two real PM BLDC motors.Design/methodology/approachAnalytical calculations take into consideration phenomena occurring during windings switch‐overs and impact of inductance on emerging voltage and rotational speed drops. It has been pointed out that on account of main circuit inductance, the average value of source current is less than average value of equivalent current generating electromagnetic torque. For analysis sake it has been assumed when windings are being switched‐over the current is kept constant; the motor parameters have also been assumed to be constant.FindingsA novel and accurate method of determining torque‐speed characteristics of PM BLDC motor has been worked out. This method has been investigated with the help of motor computer models implemented in Matlab/Simulink software and the obtained results have been subsequently compared with results of laboratory tests of two commercially available PM BLDC motors.Research limitations/implicationsThe object of the research was brushless DC motor with permanent magnet excitation. The impact of windings switch‐overs on torque‐speed curves of the motor has been analysed. Analytical method which makes it possible to determine torque‐speed curve of this motor very easily has been elaborated. Computer model of PM BLDC motor for Matlab/Simulink software has also been worked out. Extensive simulations helping to verify the proposed method have been run. Results of analysis and simulation tests have been verified by means of laboratory tests of two commercially available PM BLDC motors.Practical implicationsPM BLDC motors are used more and more widely. The new method of determining PM BLDC motors torque‐speed curves will facilitate analysis and design of drive systems utilizing these motors and will also speed up calculations.Originality/valueThe presented method of determining torque‐speed curves of PM BLDC motor is novel and much more precise than methods commonly used nowadays. Recognized methods usually neglect impact of inductance on motor properties.

Design of direct linear drives for manufacturing

The design of direct linear drives for manufacturing is considered. The benefits of synchronous machines with permanent-magnet excitation are outlined. The basic stages in the design of linear synchronous machines with permanent-magnet excitation are presented, and development results are discussed.

Analytical Design of Flux-Switching Hybrid Excitation Machine by a Nonlinear Magnetic Circuit Method

The flux-switching hybrid excitation machine is an interesting brushless machine with magnets and excitation windings in the stator. Due to the unique structure and hybrid excitation, the assignment for electric excitation and permanent magnet excitation becomes a difficult issue. To explore a rapid design method, the nonlinear magnetic circuit analytical model of the element machine has been developed, which introduces the technologies of critical regions subdivision and iterative solutions for magnetic permeability into the magnetic circuit model. Then, the ampere turns of electric excitation, the recommended value of initial magnetic bridge flux density, the influence of stator yoke thickness on magnet dimensions and field regulating coefficient are also included. Finally, the finite element analysis and the experimental results are presented. The proposed method is not only reasonable and effective but also efficient, which provides a reference for the flux-switching hybrid excitation machine (FSHM) design and performance analysis.

Optimization Design and Research of a Hybrid Excitation Compulsator

A compulsator is the best pulse power supply of an electromagnetic gun, into which the energy storage, electromechanical energy conversion, and pulse shaping are integrated. Compulsators were usually electrical excitations. A permanent magnetic excitation is introduced to simplify the structure and remove brushes and slip rings based on an individual electrical excitation compulsator. The existent hybrid excitation compulsator is analyzed, and some experiments are performed. Some resulting problems are presented, such as the no-load voltage waveform distortion, the inhomogeneous magnetic field distribution, and the complicated end compensation structure. The hybrid compulsator is optimized by arranging its armature and field windings in different form, and increasing the axial length of shield instead of the original structure. The influences on permanent magnet (PM) during high-current pulse discharge are researched, and the method to check the safety of the PM is presented. The self-excitation control mode of experimental prototype is developed. The special self-excitation process and realization mode are elaborated. Comparing with electrical excitation compulsators, seed current is not required during which the hybrid excitation compulsator establishes the self-excitation process.

A Multiobjective Approach for Designing the Rotor of Brushless Motors

This paper presents a multiobjective formulation for the topological design of synchronous motors. The developed torque of a motor is broken into two components: the torque due to the permanent magnet excitation and the torque due to the magnetic reluctance. In addition, topological gradients of the two torque components as objective functions are derived respectively using an adjoint variable method. Instead of simply maximizing the total torque, these two torque components are treated as different objectives in the design, thus a Pareto front of different topologies of rotor design can be achieved.

Speed Range Extension for Simplex Wave Winding Permanent-Magnet Brushless DC Machine

A new speed range extension method for the simplex wave winding permanent-magnet (PM) brushless DC machine is proposed in this paper. The machine is with PM excitation, electric commutation, and close-connected winding identical to the brushed DC machine (see Zhu , “A new simplex wave winding permanent-magnet brushless DC machine,” IEEE Transactions on Magnetics, vol. 47, no. 1, pp. 252-259, Jan. 2011). By properly controlling the status of power electronic switches, the number of coils being connected into the equivalent circuit can be reduced, and thus the speed range will be extended. For the prototype of 10-pole and 11-slot machine, besides operating with all the 11 coils, the machine can be controlled with only 8 or 6 coils operating for wider speed range. The experiments verify the new speed range extension method for simplex wave winding PM brushless DC machine.

Analysis of the methods of calculation and simulation of DC motors with permanent magnet excitation

The paper considers the basic methods of calculating the DC motors with permanent magnet excitation. It is shown that the most accurate data on the characteristics of DC motors with permanent magnet can be obtained by modeling their magnetic and electrical fields in windings. The article gives a comparative analysis of the possible methods of modeling.

Investigation on Flux Characteristics of Field Excitation Flux Switching Machine with Single FEC Polarity

Flux switching machines (FSMs) that consist of all flux sources in the stator have been developed in recent years due to their definite advantage of single piece robust rotor structure suitable for high speed applications. They can be categorized into three groups that are permanent magnet (PM) FSM, field excitation (FE) FSM, and hybrid excitation (HE) FSM. Both PMFSM and FEFSM has only PM and field excitation coil (FEC), respectively as their main flux sources, while HEFSM combines both PM and FECs. Among these FSMs, the FEFSM offers advantages of low cost, simple construction and variable flux control capabilities suitable for various performances. In this paper, design study and flux interaction analysis of 24S-10P FEFSM with single direction of FEC winding is presented. Initially, design procedures of the FEFSM including parts drawing, materials and conditions setting, and properties setting are explained. Then, coil arrangement tests are examined to confirm the machine operating principle and position of each armature coil phase. Finally, the flux interaction between DC FEC and armature coil, FEC flux capabilities at various current condition, and initial torque are also investigated.

Electromagnetic Field Analysis of Hybrid Excitation Vehicle Generator with Low Voltage and High Current

In order to further improve the power supply system reliability of low voltage high current vehicle generator, hybrid excitation is used and the permanent magnets are added between the main magnetic poles body and pole shoes. Aiming at reply the problem of limited installation space, the asymmetric pole structure, non-uniform commutating pole, single wave windings playing a role of the pressure line and oblique brush etc are investigated for improving commutation. This paper researched on the distribution of the flux line, the waveform of the air gap magnetic field, and analysis inner magnetic field at the loading by hybrid excitation and no loading by permanent magnet excitation alone respectively with the method of finite element. The results reveal that the magnetic field established by several excitation systems is still symmetric and uniform although the asymmetric structure, so it ensures the provision of suitable medium space for mechanical and electrical energy conversion. By comparing the permanent magnets excitation alone and hybrid excitation in a generator magnetic field distribution and air gap magnetic field waveform, the permanent magnet excitation and electricity excitation realized the superposition of magnetic field, and common establish main generator magnetic field. Hybrid excitation also reduces the current density of excitation coils and improves the heat dissipating performance compared with electrically excited alone. Through the performance analysis of the hybrid excitation, the output voltage waveform is very stable. The curve of auxiliary excitation current along with velocity variation provide important basis for excitation control devices and the development of control algorithm. It will help to improve the stability, reliability and security of the generator, the results can provide key technical support to the development of low-voltage high-current hybrid excitation vehicle generator.

Permanent-Magnet Flux-Switching Synchronous Motor Employing a Segmental Rotor

This paper introduces a three-phase segmental-rotor flux-switching synchronous motor employing permanent-magnet (PM) excitation in the stator. Flux-switching machines operate with bipolar flux and flux linkages and are therefore associated with high torque densities. Employing a segmental rotor significantly alters the scheme for flux switching from that with toothed rotors but provides a means to deploy radially acting magnets in the stator teeth. The whole arrangement presents advantages of fault tolerance capability, brushless operation, easy cooling, and simplicity of construction. A three-phase motor is developed on a 12-tooth stator with six radial magnets and a rotor with eight segments. Design considerations are applied to the location and shape of the magnets. The developed design has attraction for low-cost applications as the torque capability per unit mass of magnets deployed is found to be about 1.4 times as much as that for conventional PM synchronous motors of the same general size. Measurement results on experimental machines show that the segmented-rotor motor with PM excitation can achieve nearly twice the torque density of the similar-sized segmented-rotor motor with a dc field winding.

Novel Modular-Rotor Switched-Flux Permanent Magnet Machines

Switched-flux permanent magnet (PM) (SFPM) machines have attracted considerable interest in recent years, since the flux focusing can be utilized, both armature windings and PM excitation sources are on the stator, while the salient pole rotor is very simple and robust. In SFPM machines, the high variable flux densities throughout the stator core result in iron loss being a significant proportion of the total losses. This paper presents a novel modular-rotor SFPM machine that facilitates a reduction in iron loss for a marginal reduction in output torque. The modular rotor also offers a reduction in rotor mass over the conventional-rotor topology. The electromagnetic performance of both conventional- and modular-rotor SFPM machines is analyzed by 2-D finite element analyses and is verified by measurements on small-scaled prototype SFPM machines.