Permanent Magnet Brushless DC Machine Research Articles

Bidirectional Quadratic Converter-Based PMBLDC Motor Drive for LEV Application

In this study, a bidirectional DC-to-DC quadratic converter (BDQC) is designed and developed for the motoring and regenerative braking (RB) of a permanent magnet brushless DC (PMBLDC) motor for a light electric vehicle (LEV) application. A PMBLDC motor is deemed more suitable for an electric vehicle (EV) due to its high efficiency and torque density. In the present work, a BDQC of 1 kW is designed to drive a 1.1 HP PMBLDC motor through a conventional voltage source inverter (VSI). An EV’s load cycle is emulated using a highly inertial load driven by a PMBLDC motor during the converter’s boost mode operation. RB is a crucial factor in extending the driving range of EVs by efficiently utilizing battery power. The converter operates in buck mode during RB, and simultaneously, the back electromotive force (EMF) of the PMBLDC machine is boosted by the self-inductance of the PMBLDC motor and the VSI. The braking technique used in this work eliminates the traditional drawback of RB in buck mode, as the power is extracted even when the motor’s back EMF is lower than the battery’s voltage. The control strategy has been implemented using the TMS320F28335 DSP controller for a developed converter prototype of the converter and driving the PMBLDC motor. The experimental results are compared to the simulation results, and a good alignment has been found.

Brushless DC Permanent Magnet Motors State of the Art

The paper presents a study of the permanent magnet brushless DC machine, from two perspectives - from authors’ own experience in designing and manufacturing such motors, as well as from actual published research. Various constructive topologies and how they influence BLDC operation, windings used with emphasis on slot, concentrated windings, are also presented. The following part describes current techniques used for enhancing BLDC limited maximum speed, such as phase advance and dwell control, somewhat similar to flux weakening in AC permanent magnet brushless motors. The paper concludes with presentation of several methods used for sensing BLDC rotor position. Overall, the authors’ intention publishing this paper was to provide an insight regarding current BLDC development, as well as to assist in making documented choices when using BLDC in specific applications.

Design of flux‐weakening space vector control algorithms for permanent magnet brushless DC machines on suitable synchronous reference frames

The design of space vector control (SVC) systems suitable for flux-weakening operation of permanent magnet brushless DC machines (PMBDCMs) is presented in this study. The proposed design approach enables overcoming the critical issues arising from the non-linearities of PMBDCM voltage and torque equations; these issues derive from the trapezoidal shapes of back-emfs and affect PMBDCM constraint management significantly. The SVCs presented in this study have been developed within two different synchronous reference frames, both of which enable distinguishing torque and demagnetising current components clearly. Therefore, reference torque current component is determined in accordance with PMBDCM torque demand, while reference demagnetising current component is computed through a voltage follower PI regulator, which processes the voltage deficit detected on the DC-link. In this regard, a novel synchronous reference frame is proposed in this study, which improves PMBDCM constraint management and results into a wider constant-power speed range, but at the cost of some torque ripple. The enhanced performances achievable by SVC approaches are highlighted by numerical simulations, which regard the comparison among the SVCs and an SVC with no flux-weakening capability, at different operating conditions.

Dynamic Response Enhancement and Fault Protection of Boost Converter-Fed Brushless DC Motor in Aerospace Applications

The permanent magnet (PM) brushless DC (BLDC) machine has been widely used in various applications due to its high reliability and simplicity. In aerospace applications, the requirements of its dynamic acceleration characteristic and fault protection capability have further increased. This paper proposes an optimized inverter topology composed of a boost converter, two protective power switches, and a three-phase full bridge for the dynamic response improvement and fault protection capability enhancement of PM BLDC machines. The corresponding drive logic, control method, and protection strategy are designed to develop a drive system for an aeronautical fuel pump. The response performance is significantly improved in handling under-voltage and over-rated conditions by utilizing the boost converter during different processes, and the protection capability is enhanced to deal with over-voltage and over-current fault isolation. A boost converter-fed BLDC pump system prototype is built and tested. It is concluded that the simulation and experiment results verify the rationality and validity of the proposed method.

Analysis and Design of PMBLDC Motor for Three Wheeler Electric Vehicle Application

This paper deals with analysis and design of permanent magnet brushless dc machine (PMBLDCM), primarily aimed for three wheeler applications. The motor sizing accounts for the forces acting on the motor and the design variables such as number of stator and rotor slots, stator and rotor dimensioning, air-gap approximation, slot sizing, flux per pole and permanent magnet sizing has been explained using simplified equations. The designed motor rated at 1.5 kW, 3000 rpm, 120 V radial flux surface mounted permanent magnet rotor, is then assessed using analytical tools for design such as ANSYS’s RMXprt to verify the analytically obtained results. These results are then verified using the computer aided analysis tool, finite element analysis, using ANSYS Maxwell, to obtain the electromagnetic characteristics of the motor for further modification of design.

Permanent magnet brushless DC machines (PMBLDC) for general purpose - part II, results of laboratory measurements

The paper presents research on properties of the low power PMBLDC motor, designed to drive a bicycle. In the first part of the study the conditions of the torque generation were analyzed. The purpose of the article is to provide new information about PMBLDC motors and their properties. In the first part of the article the motor construction and torque generation in it were studied. Also the methodology of analysis were presented. The second part of the article will treat on the measurements and calculations of EMF, currents, voltages, and electromagnetic torque.

Permanent magnet brushless DC machines (PMBLDC) for general purpose – part I, the specificity of construction, methods of analysis

The paper presents research on properties of the low power PMBLDC motor, designed to drive a bicycle. In the first part of the study the conditions of the torque generation were analyzed. The purpose of the article is to provide new information about PMBLDC motors and their properties. In the first part of the article the motor construction and torque generation in it were studied. Also the methodology of analysis were presented. The second part of the article will treat on the measurements and calculations of EMF, currents, voltages, and electromagnetic torque.

The peak current control of permanent magnet brushless DC machine with asymmetric dual-three phases

The asymmetric dual-three phase BLDC motor has two sets of stator windings, in which the back EMF coefficients are different. This paper takes advantage of the asymmetric dual-three phase BLDC motor's structural features and proposes a new method for the accelerated problem of the BLDC motor operating in the high speed and the constant electromagnetic power. The dual phase windings of the BLDC motor are integrated into the circuit in the starting stage. When the motor's back EMF value is equal to the terminal voltage value, switch off a set of RST three phase windings whose back EMF coefficient is bigger and make the other set of stator winding UVW with smaller back EMF coefficient continue to operate under the rated power. As the motor rotor speed continues to increase, the electromagnetic torque remains unchanged. By using the peak current control strategy, we can deduce that the phase current of the UVW three-phase winding is twice the RST three-phase winding when the asymmetric dual-three phase BLDC motor operates at high speed and constant power.

Braking Torque Due to Cross Magnetization in Unsaturated IPM BLDC Machines and Its Mitigation

Cross magnetization (CM) is an inevitable phenomenon in electrical machines. It is more prominent in interior permanent magnet (IPM) brushless dc (BLDC) machines. This is because PMs demagnetize in overloaded and saturated conditions. It leads to cross coupling between the direct and quadrature-axes quantities, and a decrease in the resultant air-gap flux-density distribution under saturated conditions. In this paper, it is shown that CM leads to braking torque even in unsaturated IPM BLDC machines. Furthermore, the effect of CM on flux linkage, electromotive force, and dynamic torque is presented. Its mitigation using suitable selection of slot–pole combination is presented. It is observed that odd slot–pole combinations are least affected, and even slot–pole combinations are severely affected by CM. Furthermore, it is found that the overlap area of rotor pole arc with the stator pole arc influences the severity of CM, more particularly in fractional slot–pole combination machines. To verify these claims, finite-element method is used for modeling and analyzing various slot–pole combinations of a spoke-type IPM BLDC motor. The results obtained from these simulations are validated with a fabricated reference prototype, which support the claims.

A Novel Dual-Winding BLDC Generator–Buck Converter Combination for Enhancement of the Harvested Energy From a Flywheel

This paper proposes a novel flywheel energy storage system which results in up to 20% enhancement in the harvested energy from the flywheel, in comparison with the existing schemes. Generally, boost converters are used for boosting the voltage in such systems. Major limitation of a boost converter is the dependency of its maximum achievable voltage gain on the ratio of its source resistance to load resistance which limits the amount of harvested energy from a flywheel and lowers the efficiency at low input voltages. The proposed scheme uses a novel and unique combination of dual armature winding permanent-magnet brushless dc machine and a buck converter to maintain the dc-bus voltage to overcome the limitations of the boost converter. Further, the new scheme helps in reducing the armature current loading on the machine to a large extent when it is being used as a generator. A detailed study has been carried out and the effect of generator winding configurations and control strategies adopted in the proposed scheme are analyzed. The proposed scheme is simulated using MATLAB/SIMULINK software. A hardware prototype having 1.0 kW/200 V rating has been built. The theoretical and experimental results are found to be in agreement.

Advanced Design and Operation Consideration for Close-Connected Winding Permanent-Magnet Brushless DC Machine

Advanced design and operation consideration for the close-connected winding permanent-magnet brushless DC machine is proposed in this paper, including circulating current elimination, fault-tolerant control for the breakdown of a power electronic switch, and a sensorless control method. With the finite-element analysis, the influence of machine design parameters on circulating current is investigated. By properly controlling the status of power electronic switches, the coils being connected into the equivalent circuit can be changed to avoid the failure switch. Sensorless control is explored by detecting the zero-crossing point of electromotive force.

3-D Analytical Model of Helical Winding PM Machines Including Rotor Eddy Currents

Helical windings (or zigzag windings) are used in a number of applications, however, in electrical machines, mainly employed in low-power, high-speed permanent magnet (PM) brushless dc machines due to the cost effectiveness of the winding type while maintaining reasonable performance. Typically, helical windings are used for low-voltage applications due to their spiral form, which makes them most suitable for a small number of turns. In high-speed electrical machines, such a low number of turns are applicable. It is apparent that high-speed PM machines suffer from rotor eddy-current losses, which in some cases may lead to PM demagnetization due to overheating. The performance of the machine is compromised by these losses; hence, they have to be considered during the design procedure. There are many papers analyzing the magnetic field of these machines employing helical windings; however, none of them present a simple and precise electromagnetic model of a machine with the helical winding. This paper presents an analytical approach to model the resulting 3-D magnetic field of the helical winding, considering eddy currents in the conducting media of the rotor. The model is verified with the 3-D finite-element method by means of comparing magnetic field and rotor eddy-current losses.

Design Constraints of Small Single-Phase Permanent Magnet Brushless DC Drives for Fan Applications

Permanent magnet brushless dc (BLDC) machines are widely used due to various advantages such as high efficiency and high torque density, and therefore compactness as well as long expected lifetime. All of these benefits are of major interest when designing a drive for a small fan application of a few watts. This paper presents the design investigations of a small single-phase BLDC motor for such an application. Notably, it discusses different constraints which arise during the design process and which may be of special relevance due to the particular given power level and application.

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.

Power Generation in Series Mode

This article presents the development and implementation of a 20-kW permanent magnet (PM) brushless dc (BLDC) machine starter/generator system for a series-parallel 2 x 2 hybrid electric vehicle.

Artificial intelligence applications in Permanent Magnet Brushless DC motor drives

Permanent Magnet Brushless DC (PMBLDC) machines are more popular due its simple structure and low cost. Improvements in permanent magnetic materials and power electronic devices have resulted in reliable, cost effective PMBLDC drives, for many applications. Advances in artificial intelligent applications like neural network, fuzzy logic, Genetic algorithm etc. have made tremendous impact on electric motor drives. The brushless DC motor is a multivariable and non-linear system. In conventional PMBLDC drives speed and position sensing of brushless DC motors require high degree of accuracy. Unfortunately, traditional methods of control require detailed modelling of all the motor parameters to achieve this. The Intelligent control techniques like, fuzzy logic control/Neural network control etc. uses heuristic input---output relations to deal with vague and complex situations. This paper presents a literature survey on the intelligent control techniques for PMBLDC motor drives. Various AI techniques for PMBLDC motor drives are described. Attempt is made to provide a guideline and quick reference for the researchers and practicing engineers those are working in the area of PMBLDC motor drives.

Design and analysis of a new multiphase polygonal-winding permanent-magnet brushless DC machine

In this paper, a new multiphase polygonal-winding permanent-magnet brushless dc (PMBDC) machine is proposed and analyzed. The originality of the proposed machine lies on the multiphase polygonal-winding stator and the surface-inset permanent-magnet rotor. Because of its unique structure and operating principle, a circuit-field-torque coupled time stepping finite-element method is also employed for analysis. The designed machine is prototyped and the analysis is verified by experimentation.

Design and analysis of a new permanent magnet brushless DC machine

A new permanent magnet (PM) brushless DC machine with a unique feature of flux regulation is proposed in this paper. The originality is that the air-gap flux of the machine is generated by both the PM excitation and the specially controlled stator current under the same PM pole. The machine possesses advantageous characteristics of both the PM brushless DC machine and the DC series machine. The rotor configuration and principle of operation are so novel that the magnetic field distribution and performances of the machine are analyzed by use of a time-stepping finite element method. The theoretical calculation is also verified by experimental measurement.

Optimization of the skew angle of rotor poles in permanent magnet machines based on the inverse problem method

This paper presents optimization of the skew angle of rotor magnetic poles in permanent magnet brushless DC machines. The skew angle optimization is achieved using the gradient based inverse problem methodology. The paper introduces the armature winding flux linkages and associated induced EMFs for the first time as the object function. Meanwhile, this object function involves the use of stored energy and excitation perturbation techniques. An example 1.2 hp permanent magnet brushless DC machine is used to demonstrate the validity and usefulness of the method.

Electric machinery parameters and torques by current and energy perturbations from field computations. II. Applications and results

For pt.I see ibid., vol.14, no.4, p.1507-13 (1999). The theoretical developments and formulations of part I of these two-part companion papers are applied here to three practical examples, namely a 15-HP permanent magnet brushless DC machine, a 1.2 HP three phase induction motor, and a 14.3 kVA modified Lundell alternator. The excellent correlation between computed and test results for inductance profiles, steady-state terminal voltage waveforms and steady-state time-domain developed torque profiles verify the reliability and well posedness of the energy/current perturbation approach in electric machinery problems involving both 2D-FE and 3D-FE magnetic field solutions.