Search

In recent years, electric vehicles are the large-scale spread of the transportation field has led to the emergence of brushless direct current (DC) motors (BLDCM), which are mostly utilized in electrical vehicle systems. The speed control of a BLDCM is a subsystem, consisting of torque, flux hysteresis comparators, and appropriate switching logic of an inverter. Due to the sudden load torque variation and improper switching pulse, the speed of the BLDCM is not maintained properly. In recent research, the BLDC current control method gives a better way to control the speed of the motor. Also, the rotor position information should be the need for feedback control of the power electronic converters to varying the appropriate pulse width modulation (PWM) of the inverter. The proposed optimization work controls the switching device to manage the power supply BLDCM. In this proposed self-ameliorate soft switching (SASS) system is a simple and effective way for BLDC motor current control technology, a proposed control strategy is intended to stabilize the speed of the BLDCM at different load torque conditions. The proposed SASS system method is analyzing hall-based sensor values continuously. The suggested model is simulated using the MATLAB Simulink tool, and the results reveal that the maximum steady-state error value achieved is 4.2, as well as a speedy recovery of the BLDCM's speed. [ABSTRACT FROM AUTHOR]

This paper presents a novel and exhaustive investigation involving in-depth analysis, performance evaluation and comparative study of two 0.75 hp, 4-pole, 1500 rpm laboratory prototypes of Brushless DC (BLDC) motors of identical nominal ratings with surface and interior permanent magnet rotor structures having the same stator and winding (integral slot distributed winding). Both the motors were designed and developed in the lab. The major electrical variables (such as rated power, speed, voltage, current, number of poles, etc.) and the stator (such as core material, stator lamination, stack length, winding pattern and wire gauge) of the fabricated prototypes have also been kept identical to pin-point the direct influence of the two different rotor configurations (viz., surface vs interior permanent magnet) on the parameters, performance and operation of these BLDC motors. Additionally, to ensure unbiased basis for appropriate comparison, the overall volumes of magnets/pole in both the motors have also been kept similar. A detailed comparison of different quantities like air-gap flux density distribution, THD in induced voltage, torque ripple, losses and efficiency, torque–speed characteristics with field-weakening capability, steady state parameters at different operating conditions, etc. has been conducted for the said motors and the salient points duly highlighted. The vulnerability of the permanent magnets to demagnetisation based on armature reaction, particularly during a sudden fault, has also been investigated in both the cases. The theoretically determined parameters and analytically evaluated performance figures have been verified through standard FEM packages, and later validated experimentally on the fabricated prototypes. Very good mutual agreement has been observed between predicted and experimental values. [ABSTRACT FROM AUTHOR]

This study presents a novel online, accurate and simple model‐based maximum torque per ampere (MTPA) strategy for input–output feedback linearisation control of induction motor (IM) drives. Despite conventional MTPA control principles which are under the assumption of iron loss neglecting, the proposed strategy takes iron loss effect into account. This study highlights the iron loss influence on MTPA scheme. Firstly, the cross‐coupling effects in the IM model and torque non‐linearity due to the iron loss in torque–speed characteristics of the IM are discussed. The criterion for the MTPA scheme is then introduced and investigated by gradient approach so that when the gradient vectors of the torque and stator current magnitude are parallel, the MTPA strategy is satisfied. Finally, to confirm the validity of the proposed control scheme, experiments are carried out. [ABSTRACT FROM AUTHOR]

This study proposes several easy-to-implement control strategies when seven-phase axial flux brushless DC machines with trapezoidal back electromotive forces operate in normal and faulty modes by taking into account constraints on voltage and current. The constraints are related to the converter and machine design in terms of maximum values of current and voltage. The considered faults are cases in which one or two phases of the machine are open-circuited. Numerical computations based on analytical formulations are applied to obtain torque-speed characteristics, including the flux-weakening operation. The methods determine current references to ensure the torque optimisations while currents and voltages are within their limits. The usefulness of the methods is verified by numerical results.

This study proposes several easy-to-implement control strategies when seven-phase axial flux brushless DC machines with trapezoidal back electromotive forces operate in normal and faulty modes by taking into account constraints on voltage and current. The constraints are related to the converter and machine design in terms of maximum values of current and voltage. The considered faults are cases in which one or two phases of the machine are open-circuited. Numerical computations based on analytical formulations are applied to obtain torque-speed characteristics, including the flux-weakening operation. The methods determine current references to ensure the torque optimisations while currents and voltages are within their limits. The usefulness of the methods is verified by numerical results. [ABSTRACT FROM AUTHOR]

This study aims to investigate, analyze, discuss and illustrate an effective and reliable fast braking system used in a three-phase induction motor by combining two or more different conventional braking methods such as dynamic-plugging and electromagnetic-plugging. The plugging process is implemented by disconnecting one of the stator phases and connecting it with an electromagnetic brake while interchanging the other two phases. The dynamic process is executed by inserting high resistance in the rotor circuit of the motor. The performance of the torque-speed characteristics of the induction motor will be studied and analyzed through the dynamic process. Mathematical models have been developed and simulated. Results show that the braking process time is greatly reduced. [ABSTRACT FROM AUTHOR]

This paper proposes a novel flux adjustable permanent magnet coupler (PMC) with a double-layer permanent magnet rotor (PMR). The PMR, as the only excited source, is divided into the inner and outer parts. The PMs in both parts are, respectively, staggered arrangement by N- and S-poles with tangentially magnetized direction. The inner part can be controlled to rotate to adjust the relative position with the outer part to offer a controllable excitation magnetic field. Therefore, the eddy current intensity and torque can also be adjustable. The structure and operation principle of the proposed PMC are illustrated in detail. Then, to analyze the field and torque at each different relative position of the two parts of PMRs, the change period of the relative position, from N–N (and S–S) to N–S state, is divided into seven steps. The distribution of magnetic field and air-gap flux density of each relative position is analyzed in static field, and the torque–speed curves are calculated in transient field by using the 2-D finite-element method. Finally, based on the torque–speed characteristics, the influences of the structural parameters on the torque are analyzed and calculated, which can provide a reference for structural optimization design of this kind of PMC. [ABSTRACT FROM AUTHOR]

Torque-speed characteristics of an oscillating wave energy converter (WEC) is necessary to determine its optimal power point and to extract the corresponding design parameters for the generator and power converters used to generate power from the WEC. In this paper, analytical expressions for the mechanical torque on the WEC due to the oscillating surge of seawater are derived, and the dynamic model of the WEC is developed. A method for hardware emulation of the WEC is proposed by controlling the torque of an electric motor. The reference torque of the motor is derived by solving the mechanical dynamics of the WEC system in a real-time computing device considering a typical sea wave input. The emulated WEC dynamics is validated through variable loading on a generator coupled with the emulator. Experimental results support the existence of an optimal power point of the derived WEC model. [ABSTRACT FROM AUTHOR]

The absence of high-cost rare-earth magnet on the rotor of Synchronous Reluctance machine makes it one of the best option for an actuator in applications with high ambient temperature. Combined with an optimized rotor structure, it can deliver good performance. In the early design phase of the machine, development cost reduction of prototyping and testing can be obtained by having a fast electro-mechanical model that can evaluate the machine's essential performance: operating envelope, power factor and efficiency. Therefore this study proposes a fast analytical tool that evaluates the electro-mechanical performance of a given Syncrel machine. Experimental evaluations done on a prototype machine has proven the validity and robustness of the tool. The resulting tool is ready to be used for fast electro-mechanical performance evaluation of any Syncrel machine topology with any power supply and control variations. [ABSTRACT FROM AUTHOR]

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper explains the reason for the difference in maximum torque-speed characteristics and power factor of IM between the motor and generator operation modes and investigates the influence of machine design parameters on the difference, such as stator resistance, rotor resistance and iron loss etc. An analytical mathematical model based on the dq reference frame is employed for investigation. It is shown that the difference in torque-speed characteristics between the motor and generator operation modes is mainly caused by the opposite direction of q -axis current and affected by stator and rotor resistance values. Finally, analytically calculated torque-speed characteristics of a 12 kW IM in the motor and generator operation modes are verified by finite element analyses. [ABSTRACT FROM AUTHOR]

This paper presents the comparison of three‐phase and five‐phase permanent magnet assisted synchronous reluctance motors (PMa‐SynRM) in terms of their design and performance characteristics. With higher fault tolerant capability, efficiency, and reliability, the five‐phase PMa‐SynRM can be a better substitute when compared with the three‐phase PMa‐SynRM in critical applications where safety is top priority. In this study, for a fair comparison, same design procedure using in lumped parameter modelling is followed in developing the three‐phase and five‐phase PMa‐SynRMs. The models are optimised to minimise cost and maximise efficiency. For further detailed comparison of the three‐phase and five‐phase PMa‐SynRMs, two‐dimensional finite element analysis (FEA) is utilised. Performance characteristics such as torque pulsation, back electromotive force, flux linkage, d‐ and q‐axis inductances versus their respective currents, cogging torque, efficiency plot, and torque‐speed characteristics are intensively simulated through FEA. The optimised three‐phase and five‐phase PMa‐SynRMs are fabricated with the same power rating (3 kW) and same volume. Experimental tests are conducted on the prototypes to validate the simulation results. [ABSTRACT FROM AUTHOR]

Efficiency maps have long been used by engineers to understand the topographical behavior of their machinery. Most commonly, efficiency maps have been generated for internal combustion engines, where the torque-speed curve for the engine shows the wide-open-throttle line with constant efficiency lines drawn beneath this maximum operating limit. From such maps, engineers have been able to determine the most efficiency operating point for the engine, given a desired output power (torque and speed). There currently exists a great interest in using hydrostatic transmissions for improving the operating efficiency of an internal combustion engine. However, efficiency maps for hydrostatic transmissions, similar to efficiency maps for internal combustion engines, do not exist in the literature and therefore it is difficult to assess the overall efficiency gains that are achieved when using a hydrostatic transmission in these applications. This paper proposes a method for generating efficiency maps for hydrostatic transmissions, and presents a typical set of maps that may be used as a first approximation for assessing transmission efficiency. The results of this paper are nondimensional and are generalized for a transmission of any size. As shown in this research, there are regimes of transmission operation in which the efficiency is nearly independent of either the output torque, or the output speed. Furthermore, it is shown that maximum operating efficiencies typically exist at high output speeds, and mid-to-high output torques. [ABSTRACT FROM AUTHOR]

In this paper, symmetrical and unsymmetrical voltage sags are classified according to the severity of the effects produced on the behavior of induction motors, using the double-cage rotor model. The analyzed variables are: current and torque peaks, and speed loss in transient and steady states. The severity of these effects is analyzed with 14640 voltage sags, both at the beginning of the voltage sag and when the voltage is recovered, by changing the type, magnitude, duration, and initial-point-of-wave. Four mechanical torque loads were used for the analysis, three with constant behavior and one with quadratic behavior. The results show the durations and initial-point-of-wave with more severe effects for each type of voltage sag. Finally, a classification that depends on the type of voltage sag and the variable of interest is obtained. [ABSTRACT FROM AUTHOR]

Switched flux permanent magnet (SFPM) machines have significant potential for many industrial applications because of their doubly salient structure, similar to switched reluctance machines. In recent years, several novel SFPM machine topologies, such as multi‐tooth, E‐core and C‐core, have been developed to reduce the usage of permanent magnet materials without sacrificing the torque capability. A comparative study of the electromagnetic performance of these topologies, together with conventional SFPM machines having different stator/rotor pole combinations, that is, 12/10, 12/13 and 12/14, is presented. In addition to open circuit and electromagnetic torque performance, their torque–speed characteristics are investigated and compared. It is found that for conventional SFPM machines, the higher the rotor pole number, the better the flux‐weakening capability, and higher maximum speed can be achieved. In contrast, owing to high d‐axis inductance in the multi‐tooth, E‐core and C‐core machines, infinite maximum speed can be obtained. Moreover, among all these machines, the multi‐tooth machine has the highest flux‐weakening factor, while the E‐core machine exhibits the largest power capability. In addition to two‐dimensional (2D) finite‐element analysis (FEA), 3D‐FEA is also performed accounting for the end effect. Finally, the torque–speed characteristics of prototype SFPM machines are measured to verify the FEA. [ABSTRACT FROM AUTHOR]

With the proposed dual-current-loop control algorithm, the torque and air-gap flux of a doubly fed induction motor are controlled directly. Compared to the singly fed permanent magnet and induction motors, the torque–speed operation region for electric vehicle/hybrid electric vehicle applications is nearly doubled with the proposed dual-current-loop control algorithm for a given battery voltage. Computer simulations and experimental results are provided to verify the proposed control algorithm. [ABSTRACT FROM PUBLISHER]

Induction motors are widely used in various industrial applications with different torque-speed characteristics. Since the configuration of the rotor slot has a great impact on the electromagnetic torque-speed characteristics, a design optimization process is necessary to improve the motor performance of the induction motor. The material boundaries of the rotor slot are represented by a level set function, and a voltage driven time-harmonic field analysis is performed to estimate the characteristics of the induction motor. An optimization problem is formulated to maximize the torque at one speed either a rated or starting condition constrained by the torque at other speeds, starting currents and efficiency. A level set equation with an augmented Lagrangian method is derived to find the optimal design. Optimal results are achieved by updating the sequential changes of the material region driven by the shape derivative. The design flexibility of the proposed method is confirmed to obtain National Electrical Manufacturers Association (NEMA) designs satisfying different torque characteristics. [ABSTRACT FROM AUTHOR]

This paper describes the torque-speed characteristics of a magnetic-geared motor with permanent magnets only on the high-speed rotor. This magnetic-geared motor has inherent overload protection characteristics, and the rotor slips under overload condition. The characteristics are determined by using finite element analysis under vector control. The analysis results are then verified by carrying out measurements on a prototype. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study of torque–speed characteristics and cogging torque of the fractional-slot interior permanent magnet brushless ac machines having different slot openings, viz. open slot, closed slot, and hybrid slot (sandwiched open and closed slots), and unskewed and step skewed rotors. The influence of such alternate slot openings on the magnetic cross-coupling and cogging torque is particularly emphasized. Furthermore, the repercussion of the manufacturing limitations and tolerances on the cogging torque of machines having these alternate slot openings is also investigated. The magnetic cross-coupling level and the sensitivity of cogging torque to manufacturing limitations and tolerances strongly depend on the slot opening materials. The finite-element analyses are experimentally validated. [ABSTRACT FROM PUBLISHER]

This letter presents a study of perpendicular anisotropy in Co/Ni multilayers, which could constitute a thick polarizer in spin torque oscillators or a magnetic electrode in magnetic tunnel junctions (MTJ) with perpendicular anisotropy. Perfectly square perpendicular loops are observed for as-deposited Co/Ni multilayers with various sublayer thicknesses and bilayer repetition numbers using a Pt buffer layer. An anisotropy energy of 1.0 × 106 erg·cm-3 is obtained for 9 nm thick Co/Ni multilayers. For Co/Ni multilayers deposited on MgO, no perpendicular magnetization component is observed in the as-deposited state, but it develops (even in 2.1 nm Co/Ni multilayers) after annealing at 250 °C. [ABSTRACT FROM AUTHOR]

This paper presents a control technique for torque-ripple minimization in the switched reluctance motor (SRM) drive, based on a torque-sharing function (TSF) concept. In the proposed method, the reference torque is directly translated into the reference current waveform using the analytical expression. Optimization criteria of a TSF that are concerned with secondary objectives, such as minimization of copper losses or maximization of drive performance, are described. In addition, a novel family of TSFs is introduced. An optimal TSF can be easily extracted from the proposed family to satisfy one of the secondary objectives or to create balance between more of them. Control performances of the two extracted TSFs and the two optimized conventional (linear and sinusoidal) TSFs are compared. These four TSFs keep the copper losses to nearly the theoretical minimum. Each of them provides approximately the same operation efficiency of the considered three-phase 6/4 SRM drive. However, due to extension of the commutation angle between adjacent phases, TSFs from the proposed family provide better torque-speed characteristics. Moreover, one of them expands the possible speed range of torque-ripple-free drive operation, and another one, which provides the best torque-speed characteristics, reduces the peak phase current. [ABSTRACT FROM AUTHOR]

This paper proposes an improved method for the estimation of position, velocity, and disturbance torque in a surface permanent-magnet (SPM) machine self-sensing (position sensorless) drive that uses high-frequency (HF) voltage injection. SPM machines traditionally do not have enough position-dependent signals because their symmetric rotors result in near-zero spatial saliency. A separate disturbance observer and a saliency-tracking observer with speed-varying bandwidth (BW) tuning are used together to improve the disturbance rejection performance while maintaining the accuracy of self-sensing position and velocity estimation. According to the experimental evaluation, the proposed estimation method can achieve higher BW for the disturbance estimation and decoupling which can increase the stiffness of SPM machine closed-loop self-sensing control. This paper includes experimental comparative evaluation of closed-loop encoder-based versus closed-loop self-sensing-based operation of a SPM machine drive. [ABSTRACT FROM AUTHOR]

The spin torque switching current density is measured for magnetic tunnel junctions containing a CoFeB free layer. We find that the insertion of an ultra-thin boron layer near the free layer/tunnel barrier interface gives rise to an increased resistance-area product and to a reduction in the switching current density. This is attributed to a lower tunneling matrix element near the inserted boron. As a result, the injected current is concentrated within smaller areas of the free layer, which leads to an overall decrease in the switching current density. [ABSTRACT FROM AUTHOR]

This paper presents and evaluates a novel system for testing direct-drive motors for the next generation of electric vehicles. The system is adjusted to determine motor characteristics and losses at high torque and medium speed with high accuracy. It is controlled by a custom-made program, which supports motor testing in various control modes and working regimes and under various testing procedures due to the modular program structure. The measurements are therefore repeatable, reproducible, and can be carried out in a short period of time. Regarding the problem of energy consumption, the proposed test system with two direct drive motors (instead of an industrial braking motor) results in additional savings. An additional contribution of the paper presents a system upgrade with the evaluation of the test system in terms of the A and B types of uncertainty and its confirmation with a motor mathematical model. One-to-one correspondence is confirmed without any mathematical model modifications in a short circuit test. A good agreement between measured values of different quantities and the mathematical model can be also confirmed with tests of motor losses, torque-speed characteristic, motor thermal behavior, and efficiency map. The presented tests are part of the testing procedure used during evaluation of the direct-drive motor. [ABSTRACT FROM AUTHOR]