Brushless DC Machine Research Articles

Design and Modeling of Photovoltaic System Fed Brushless DC Motor

The objective of this work is to make a study of the photovoltaic generator and converters used to supply a brushless DC machine actuating a centrifugal pump. This will be carried out by modeling and simulation of the various stages that constitute the overall system, which includes the photovoltaic source, the maximum power point tracker and the three-phase inverter with the space vector modulation scheme The simulation has been carried out using MatLab-Simulink and the results are presented for different operating conditions.

Design Optimization of a Homopolar Salient-Pole Brushless DC Machine: Analysis, Simulation, and Experimental Tests

This paper presents the design optimization and experimental tests of a homopolar brushless dc generator. To achieve the required performance within a specified space envelope, the physical dimensions of the proposed configuration were optimized utilizing 3-D finite-element analysis (FEA), subject to maximize the average output power. In this paper, the experimental study and numerical technique as two types of analyses have been utilized to evaluate the proposed machine performance. To validate the correctness of the predicted flux-linkage characteristics, the 3-D FEA method has been utilized as the numerical analysis. In this paper, for improving the flux path in the housing and reduction of the hysteresis and eddy current losses, three axially laminated flux paths are considered which connected two stator sets physically and magnetically. In this paper, regulating the terminal voltage has been investigated by employing the tunable PID controller. Tuning of the PID parameters based on an internal model strategy has been done. Subsequently, flux density in different parts of the prototype machine is measured, and also, a series of experimental tests for no-load and under-load operations at different speeds are carried out to obtain the output characteristics of the machine.

An Optimal Current Distribution Method of Dual-Rotor BLDC Machines

This paper proposes an optimal current distribution method of dual-rotor brushless DC machines (DR-BLDCMs) which have inner and outer surface-mounted permanent-magnet rotors. The DR-BLDCM has high power density and high torque density compare to the conventional single rotor BLDCM. To drive the DR-BLDCM, dual 3-phase PWM inverters are required to excite the currents of a dual stator of the DR-BLDCM and an optimal current distribution algorithm is also needed to enhance the system efficiency. In this paper, the copper loss and the switching loss of a DR-BLDCM drive system are analyzed according to the motor parameters and the switching frequency. Moreover, the optimal current distribution method is proposed to minimize the total electrical loss. The validity of the proposed method was verified through several experiments.

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.

Simplified Design and Optimization of Slotless Brushless DC Machine for Micro-Satellites Electro-Mechanical Batteries

Electro-Mechanical Batteries have important advantages compared with chemical batteries, especially in Low Earth Orbit satellites applications. High speed, slotless, external rotor, brushless DC machines are proposed and used in these systems as Motor/Generator. A simplified analytic design method is given for this type of machines and, the optimization of machine in order to have maximum efficiency and minimum volume and weight are given in this paper. Particle swarm optimization (PSO) is used as the optimization algorithm and the finite element-based simulations are used to confirm the design and optimization process and show less than 6% error in parametric design.

Efficiency Comparison between Brushless DC Motor and Brushless AC Motor Considering Driving Method and Machine Design

This paper describes an approach to establish high efficient drive such a Brushless AC (BLAC) drive by a Brushless DC (BLDC) drive. BLDC drive which is excited rectangular voltage for 120 electrical degrees per cycle is commonly used for the low cost applications of Permanent Magnet Synchronous Motors (PMSMs). This drive method contains low-order harmonics in the current waveform. These harmonics cause a mechanical vibration and the electrical losses. Therefore, BLDC drive is not applicable to the sinusoidal back-EMF machines. However, considering about a high frequency loss by the PWM carrier and also about the switching loss, BLDC drive has a potential to have higher efficiency than the BLAC drive. This paper compares the overall efficiency which includes PWM carrier frequency loss by using the coupling analysis between Finite Element Analysis (FEA) and a circuit simulator. The tested machines are two of Surface type PMSMs (SPMSM). One has a sinusoidal back-EMF waveform (BLAC machine) and the other has a trapezoidal back-EMF waveform (BLDC machine). The both driving methods of BLDC drive and BLAC drive are adapted to each machine, their efficiencies are compared by both simulation and experiments. The results show that the BLDC machine with BLDC drive has higher efficiency than BLAC machine with BLAC drive.

Obtaining the magnetic characteristics of 3/4 salient-pole brushless DC machine from 3-D FEM analysis

This paper deals with accurate electromagnetic field analysis of 3/4 salient-pole structure brushless DC generator (BLDG) with concentrated stator winding, which does not use a permanent magnet in the rotor. The permanent magnet is replaced with assisted field coil in the rotor. To evaluate the generator performance the numerical technique has been utilised. In the numerical analysis, 3-D finite element (FE) analysis has been carried out to confirm the accuracy of the predicted flux-linkage characteristics and, also an improved 3-D hybrid method coupling the FE method and boundary integral equation method to confirm the accuracy of the 3-D FE analysis has been carried out. Afterward, a series of experimental tests are performed to obtain the magnetic characteristics of the 9/6 configuration by same structure, comparing, correcting, and discussing the results with those of 3-D FEM analysis.

High-Efficiency Current Excitation Strategy for Variable-Speed Nonsinusoidal Back-EMF PMSM Machines

Opportunities for energy efficiency improvements in motor drives remain a forefront topic of interest in recent times due to their extensive use and applications. Then, it is the right juncture to revisit various stator current excitation strategies and their impact on the efficiency of brushless dc (BLDC) machines favored in high volume variable speed applications. BLDC machines with nonsinusoidal back electromotive force (EMF) are considered in this paper, and the influence of sine, square, and nonsinusoidal harmonic current on their performance is investigated. To facilitate such a study, analytical expressions for the generalized back EMF of all the three excitation schemes have been derived to highlight their influence on torque ripple and motor harmonic losses, thus leading to efficiency evaluation. An analytical approach on the estimation of iron losses under loaded operation has been elaborated to highlight the impact of stator current harmonics on the efficiency of the motor. Analytical as well as experimental results show that it is advantageous to use the nonsinusoidal harmonic injection (NSHI) scheme in the speed range until the sum of the drive conduction and stator resistive losses exceeds the iron losses of the machine. When iron losses become dominant, the algorithm is modified to sinusoidal current control, thus maintaining higher efficiency operation. To achieve such an operation, a hybrid control scheme encompassing sinusoidal to NSHI field-oriented sensorless controller has been implemented.

Hall effect sensor based space vector PWM control of permanent magnet synchronous machine

This paper proposes a space vector control of permanent magnet synchronous machine (PMSM) based on Hall effect sensor, which is very useful in practical applications due to the exactly same hardware structures between PMSM and brushless DC (BLDC) machine. This proposed method can be considered as an intermediate stage of development between the general incremental encoder based and sensorless based PMSM control methods. Because the Hall effect sensor is an absolute position sensor with 60-degree resolution, the position initialization process is not needed and the reversal rotation risk can be avoided. To improve resolution the interpolation method implemented by software is employed. Finally the high performance of this proposed method is validated by some experimental results.

Integrated Optimization of Two Design Techniques for Cogging Torque Reduction Combined With Analytical Method by a Simple Gradient Descent Method

This paper presents an integrated optimization process to minimize cogging torque in permanent-magnet (PM) machines by a simple Gradient Descent method. The presented optimization method can be easily achieved in machine design. The design techniques of nonuniformly distributed magnets and teeth are presented to illustrate the optimization process. First, with the assistance of an analytical model deduced, the initial solution and feasible domain of the optimization can be easily identified. Then a simple Gradient Descent method is combined with finite element analysis to perform the optimization within the identified feasible domain. Four representative PM machines-including surface-mounted permanent-magnet synchronous machine (SPMSM), brushless DC machine (BLDC), and interior permanent-magnet synchronous machine (IPMSM)-are designed and optimized by the presented method, respectively. The results verify that the presented optimization process can greatly reduce the cogging torque in PM machines. In addition, it is easily achieved and very time-saving. At last, the influence of the nonuniformly distributed magnets method on load torque is examined.

Position estimator for a brushless‐DC machine using core saturation and stator current slopes

Purpose – This paper is devoted to the investigation of position estimation for a brushless DC machine using only their stator currents. The first application is for a hybrid electric vehicle, where the generator will be used as a motor to start the internal combustion engine (ICE).Design/methodology/approach – This paper describes how to estimate the rotor position of a brushless DC (BLDC). Two different strategies, both based on stator currents, will be used: one for low speeds to start the ICE, and one for normal speeds for future applications in a pure electric vehicle (EV). The first one uses an estimation method based on core saturation and the second one is based on the determination of the current slopes on two of the three phases. The algorithms proposed neither needs to measure any machine parameters, nor the back emf. The methods use the information contained in the current magnitudes and slopes, and the machine mechanical speed. The system was implemented using a Digital Signal Processor (TMS3...

Induction machine performance with fractional‐slot concentrated windings

Purpose – The purpose of the paper is to investigate the performance of induction machines with fractional‐slot concentrated‐windings.Design/methodology/approach – This paper examines induction machine performance with fractional‐slot concentrated windings using the standard distributed lap windings as reference. Four designs are compared and various performance tradeoffs highlighted. The first machine has integral‐slot distributed 2 slots/pole/phase lap winding and it serves as the reference winding. The second machine has a double‐layer 1/2 slot/pole/phase winding, a workhorse for brushless DC machines. The third machine has double‐layer 2/5 slot/pole/phase winding. Lastly, the fourth machine has single‐layer 2/5 slot/pole/phase windings. The comparison includes torque‐speed curves (including the effects of major space harmonic components), rotor bar losses, and ripple torque levels.Findings – Based on the analysis results presented here, the traditional distributed lap winding is proven to be superior ...

A Modified C-Dump Converter for BLDC Machine Used in a Flywheel Energy Storage System

This paper presents a modified C-dump converter for brushless DC (BLDC) machine used in the flywheel energy storage system. The converter can realize the energy bidirectional flowing and has the capability to recover the energy extracted from the turnoff phase of the BLDC machine. The principle of operation, modeling, and control strategy of the system has been investigated in the paper. Simulation and experimental results of the proposed system are also presented and discussed.

Odd Stator Slot Numbers in Brushless DC Machines—An Aid to Cogging Torque Reduction

Brushless permanent-magnet dc machines often use an integral number of slots per pole (e.g., 3 slots/pole) with fully pitched coils in order to obtain a good trapezoidal back-electromotive-force (emf) waveform. However, this can lead to high cogging torque and load torque ripple. A simple solution is to add one additional slot so that the reluctance slotting that causes the ripple is removed, but the winding pattern is closely retained. This paper illustrates that simple design modification, where one additional slot is used so that the machine does not have an integral number of slots per pole. In this paper, the arrangement is analyzed using simple winding analysis and a finite-element analysis which gives more preciseness to calculations. It is found that there is a substantial reduction in cogging and load torque oscillation, thus proving the principle. However, the stator windings are slightly unbalanced and this can lead to vibration. This is also investigated and the resulting unbalanced magnetic pull under load is found to be present but of a low magnitude.

Optimal Design of Radial-Flux Toroidally Wound Brushless DC Machines

Toroidally wound brushless dc (BLDC) machines are compact, economical, and can operate across large air gaps. In this paper, we provide analytical design equations for a radial-flux toroidally wound BLDC machine. The validity of the design equations is checked against finite-element analyses (FEAs) and experiments. It is found that the motor constant calculated by the design equations is off only by 5% from the results by the FEAs or experiments. We also provide an optimization metric that corresponds to the maximization of machine torque while maintaining minimum power loss. Two optimal design cases are presented.

A New Simplex Wave Winding Permanent-Magnet Brushless DC Machine

A new simplex wave winding permanent-magnet (PM) brushless DC machine is proposed in this paper. Besides PM excitation and electric commutation, the machine has close-connected winding identical to the brushed DC machine. By properly controlling the power electronic switch status, the current direction of coils under N or S pole is unchanged. Thus, the new machine's operation principle is exactly as same as the brushed DC machine. Furthermore, as the adoption of PM and electric commutation, the new machine can be designed with larger pole number and lower slot number per pole, which respectively leads to less iron yoke and shorter end winding. Therefore, the proposed new machine not only keeps the characteristics of a brushed DC machine, but also improves the efficiency and power density. A 200 W, 10-pole, and 11-slot new machine is designed, prototyped, and tested to verify the analysis.

Dual-mode switching technique for reduction of commutation torque ripple of brushless dc motor

In this study, the reduction of commutation torque ripple because of phase commutation of brushless dc (BLDC) motor is described. In a conventional three-phase BLDC machine with 120° electrical conduction, commutation torque ripple occurs because of changeover of load current from one phase to another at every 60 electrical degrees. Similar is the case for 180° conduction mode because of change of phase currents at 60° intervals. A detailed analysis shown in this study reveals that the torque ripple reduces for 180° switching mode at higher speeds because of reduction of both torque ripple magnitude and commutation time, compared to the 120° conduction mode of the inverter. In this study, a dual-mode switching technique is proposed to optimise the commutation torque ripple of the machine. Suitable computer simulations and experiments are performed to validate the proposed concept.

Toroidally-Wound Self-Bearing BLDC Motor With Lorentz Force

Self-bearing motors (SBM) use a single magnetic structure for rotational motoring as well as for noncontact levitation. They are sometimes referred to as bearingless motors or combined motor-bearings. In this paper, we propose a new type of self-bearing motors based on toroidally-wound brushless DC machines. This type of SBM can be made to be passively stable in the axial direction and for out-of-plane rotations. To achieve self-bearing operation, we derive a force-current model and show that the levitation force is decoupled from the rotational torque. To overcome the singularity problem in the force-current model, we propose a phase selection algorithm in which the phase that may cause singularity is counted out when inverting the force-current model. Through finite element analyses and experiments, we validate the force-current model and the phase selection algorithm.

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.

Multiphase Power Converter Drive for Fault-Tolerant Machine Development in Aerospace Applications

This paper describes an experimental tool to evaluate and support the development of fault-tolerant machines designed for aerospace motor drives. Aerospace applications involve essentially safety-critical systems which should be able to overcome hardware or software faults and therefore need to be fault tolerant. A way of achieving this is to introduce variable degrees of redundancy into the system by duplicating one or all of the operations within the system itself. Looking at motor drives, multiphase machines, such as multiphase brushless dc machines, are considered to be good candidates in the design of fault-tolerant aerospace motor drives. This paper introduces a multiphase two-level inverter using a flexible and reliable field-programmable gate-array/digital-signal-processor controller for data acquisition, motor control, and fault monitoring to study the fault tolerance of such systems.