Optimal Stator Research Articles

Maximum Efficiency per Torque Direct Flux Vector Control of Induction Motor Drives

In this paper, a loss-minimizing strategy is proposed for induction motor drives to ensure maximum efficiency operation for a given torque demand. The proposed strategy directly regulates the machine stator flux, according to the desired torque, using an optimal stator flux reference. Therefore, the proposed strategy is suitable for motor control schemes that are based on direct flux regulation, such as direct torque control or direct flux vector control. The maximum efficiency per torque (MEPT) stator flux map is computed offline using the traditional no-load and short-circuit test data. An iron loss model based on the stator flux and frequency is also proposed for the calibration of the machine loss model and also for online monitoring of the iron losses during motor operation. The proposed MEPT strategy has been validated on a 2.2-kW induction machine, and the motor efficiency has been measured for different speed values and variable load conditions. The experimental results confirm the effectiveness of the proposed solution.

遺伝的アルゴリズムを用いた三自由度球面アクチュエータの磁極配置最適化

The development of multiple degree-of-freedom actuators is expected in robotics and industrial machinery fields. There remain, however, some problems in terms of the torque density, control method, and sensing systems. Under the circumstances, we are studying on a 3-degree-of-freedom outer rotor spherical actuator and its control method. We have also confirmed the characteristics employing 3D-FEM. In this paper, genetic algorithm is employed to search for the optimal stator pole arrangement which has the maximum torque constant (Instead, minimum mean current with a constant torque). Then, the effectiveness of the optimization is verified through the comparison of the mean current controlled to generate a constant torque between the optimized and the initial models.

Influence of Stator and Rotor Pole Arcs on Electromagnetic Torque of Variable Flux Reluctance Machines

The influence of stator and rotor pole arcs on electromagnetic torque of variable flux reluctance machines (VFRMs) having different stator and rotor pole combinations is investigated. Different from 6/4 stator/rotor pole switched reluctance machines, which usually employ equal stator pole arc and stator slot opening, unequal stator pole arc and slot opening can boost the torque density of the VFRM. Moreover, the optimal rotor pole arc to rotor pole pitch ratio in VFRMs is \(\sim ~1/3\) and the optimal stator pole arc is equal to or slightly smaller than the optimum rotor pole arc. For a 6-pole stator, the 4-, 5-, 7-, and 8-pole rotor VFRMs with the optimal stator and rotor pole arcs can increase the average torque by 1%, 4%, 30.7%, and 72.9% compared with those having equal stator pole arc and stator slot opening. In addition, the 6/7 stator/rotor pole VFRM exhibits the largest torque density. Prototype machines with optimal stator and rotor pole arcs are manufactured and measured to validate the analysis.

고정자 자속의 해석을 통한 직접 토크 제어 SPMSM의 최대 토크 운전

This paper proposes a maximum torque operation strategy for the direct torque control of a surface-mounted permanent-magnet synchronous motor (SPMSM). The proposed method analyzes the available operation region of the stator flux of the SPMSM under voltage and current constraints. Based on this analysis, the optimal stator flux trajectory that yields the maximum torque is obtained across the entire operation region, including constant torque and constant power regions. The proposed strategy is also applicable in the flux-weakening region II operation of the SPMSM, which has no speed limit. The validity of the proposed method is verified through experiments conducted on an 800 W SPMSM drive system.

Energy Optimal Control of Induction Motor for Electric Vehicle Drive System Base DTC

The requirements of the drive system for electric vehicle is high efficiency and fast dynamic response, an optimal control method base direct torque control is proposed to improve respose speed of energy optimal controlled induction motor. In stator flux orientation coordinate system, the loss mathematical model of the induction motor was established by analyzing the relationship between loss and motor torque, speed and stator flux, then the optimal stator flux formula is derived under different operating conditions to achieve the maximum efficiency of induction motor, the getted optimal stator flux is used as stator flux set value in DTC. Simulation results reveal that the proposed method improve the efficiency and respose spee of induction motor.

Performance improvements of a subsonic axial-flow compressor by means of a non-axisymmetric stator hub end-wall

This paper deals with the application of a non-axisymmetric hub end-wall on the stator of a single stage high subsonic axial-flow compressor. In order to obtain a state-of-the-art stator non-axisymmetric hub end-wall configuration fulfilling the requirements for higher efficiency and total pressure ratio, an automated multi-objective optimizer was used, in conjunction with 3D-RANS-flow simulations. For the purpose of quantifying the effect of the optimal stator non axis-symmetric hub contouring on the compressor performance and its effects on the subsonic axial-flow compressor stator end-wall flow field structure, the coupled flow of the compressor stage with the baseline, axisymmetric and the non-axisymmetric stator hub end-wall was simulated with a state-of-theart multi-block flow 3D CFD solver. Based on the CFD simulations, the optimal compressor hub end-wall configuration is expected to increase the peak efficiency by approximately 2.04 points and a slight increase of the total pressure ratio. Detailed analyses of the numerical flow visualization at the hub have uncovered the different hub flow topologies between the cases with axisymmetric and non-axisymmetric hub end-walls. It was found that that the primary performance enhancement afforded by the non-axisymmetric hub end-wall is a result of the end-wall flow structure modification. Compared to the smooth wall case, the non-axisymmetric hub end-wall can reduce the formation and development of in-passage secondary flow by aerodynamic loading redistribution.

Model Predictive Pulse Pattern Control for the Five-Level Active Neutral-Point-Clamped Inverter

In this paper, the recently introduced model predictive pulse pattern control (MP3C) strategy is adapted to the ACS 2000 medium-voltage (MV) drive of ABB. The drive system consists of a five-level active neutral-point-clamped (ANPC-5L) rectifier, an inverter, and an induction machine (IM). The inverter is fed with offline-computed optimized pulse patterns (OPPs) that produce minimum harmonic distortion in the stator windings of the ac machine. An optimal stator flux trajectory is calculated from these OPPs, and a trajectory controller tracks it in real time. In the proposed approach, trajectory tracking is based on model predictive control: a constrained optimal control problem is formulated and solved in real time in a computationally efficient manner. An event-based prediction horizon is employed in order to ensure fast tracking of the stator flux trajectory. The advantages of the proposed method are optimal steady-state behavior in terms of harmonic distortion and fast torque response. The method was tested on an MV ANPC-5L inverter coupled to a general-purpose 1.21-MW IM. Experimental results were obtained from this industrial setup, and they are presented in this paper to demonstrate the high performance of MP3C.

Determination of Steady-State and Dynamic Control Laws of Doubly Fed Induction Generator Using Natural and Power Variables

A doubly fed induction generator model is presented whereby the natural and power variables are the state variables. The natural variables are the electromagnetic torque (Te), the reactive torque (Tr), the magnitude of the rotor flux linkage (λr), the magnitude of the stator flux linkage (λs), and the rotor speed (ωr). The power variables are the real power (Pf) and reactive power (Qf) generated/absorbed by the grid-side converter into/from the grid. Simulation of the dynamic natural variable model of the induction machine is compared with a vector variable simulation. Steady-state operating regions are established for various power factor operations. The optimal stator power factor operation is estimated. A direct control of torque and power variables is developed. The robustness of the developed control against rotor parameter variation is investigated using small signal analysis and is compared with vector control. Results are shown for a 5-hp machine.

OPTIMAL ROBUST WIDE SPEED CONTROL OF INDUCTION МACHINE

This paper represents a robust voltage regulation algorithm for an induction machines that enable minimization of the losses and maximization of torque capability. The maximum torque of an induction machine is limited by the current and voltage constraints. Depending on rotor speed, current and voltage limits, the algorithm calculates the coupling coefficient of stator currents k, that determines the optimal stator currents (id, iq) for the maximum torque capability in whole values of the rotor speed (under the rotor base speed and in the field-weakening region). If those limits are not reached, the algorithm calculates optimal stator currents for minimization of losses of an induction machine. The block diagram of robust optimal voltage regulator is represented. The validity of proposed algorithm is demonstrated by simulation.

A Self-Learning Solution for Torque Ripple Reduction for Nonsinusoidal Permanent-Magnet Motor Drives Based on Artificial Neural Networks

This paper presents an original method, based on artificial neural networks, to reduce the torque ripple in a permanent-magnet nonsinusoidal synchronous motor. Solutions for calculating optimal currents are deduced from geometrical considerations and without a calculation step, which is generally based on the Lagrange optimization. These optimal currents are obtained from two hyperplanes. This paper takes into account the presence of harmonics in the back-EMF and the cogging torque. New control schemes are thus proposed to derive the optimal stator currents giving exactly the desired electromagnetic torque (or speed) and minimizing the ohmic losses. The torque and the speed control scheme both integrate two neural blocks, one dedicated for optimal-current calculation and the other to ensure the generation of these currents via a voltage source inverter. Simulation and experimental results from a laboratory prototype are shown to confirm the validity of the proposed neural approach.

Enlargement of the Claw Pole Motor using SMC Cores Divided in the Direction of a Circumference

Claw teeth motors have a feature that can make axial the length thin. This makes them suitable for appliances, automobile assistant machines, and small-sized industrial motors. On the other hand, there is a need to thin HEVs, elevators and large-sized industrial motors. In this study, we examined a higher output of the claw teeth motor. We arrived at the following conclusions as a result of our research. 1) The optimal stator structure was determined and the prospect of attaining the specification of 123N·m was determined. 2) A manufacturing subject called core assembly accuracy reservation, thin coil manufacture, and the rotator insertion method became clear. 3) The experimental results and the analysis results were in agreement with respect to the EMF. 4) The experimental cogging torque results and FEA results are in agreement in the 6th degree. But the 2nd and the 4th degrees of the experimental cogging torque results did not agree with the FEA results. 5) Although the core needed to be divided in the direction of the circumference for enlargement, it was clear that the influence on the torque is small. 6) Division of the core is a good solution for enlargement of the claw teeth motor.

Synthesis and analysis of a high‐performance low‐cost permanent magnet brushless DC motor

PurposeThe paper presents design development of a novel high‐performance low‐cost 6/4 pole permanent magnet brushless DC (PMBLDC) motor. The objective is to show how the cogging torque of this new design is minimised by determining the optimum stator pole arc length and the best shoe thickness.Design/methodology/approachAt the beginning a step‐by‐step design synthesis of a reference 6/4 pole PMBLDC motor with concentrated 3‐phase windings and asymmetric stator pole arcs is presented. It is followed by a full performance analysis of the reference motor. The FEM for electromagnetic field computation is employed. The characteristics of the motor are calculated and analysed. By simple variation of the stator pole geometry, two‐stage design optimisation for cogging torque minimisation is performed, and an optimised motor model is proposed. The comparative analyses of the reference and optimised motor models show the advantages of the proposed novel design.FindingsThe focus is to show the sensitivity of the cogging torque due to changes in the stator pole shoe design parameters, such as arc length and thickness, which are discretely changed inside the prescribed constraints, and the solution matrix is derived. It was found the optimised stator pole design, providing minimum cogging torque, has the original arc length 85° and pole shoe thickness 4 mm. Thus, the peak‐cogging torque from 0.294 Nm is reduced to respectable value 0.142 Nm.Originality/valueThe paper presents an original approach to synthesis of 6/4 PMBLDC new structured motor. A two‐step design procedure is introduced and optimised stator geometry is defined, minimising the cogging torque and, at the same time, improving the profile of back electromotive force (EMF) of the motor.

Level-Set-Based Optimal Stator Design of Interior Permanent-Magnet Motor for Torque Ripple Reduction Using Phase-Field Model

The interior permanent-magnet (IPM) motor is widely used in industrial applications due to its high power density. Despite this efficiency, the average torque increase achieved by the reluctance torque leads to high torque ripple, the major cause of motor noise and vibration. Therefore, many studies related to the size optimization have been performed to reduce this ripple effect. This paper suggests an optimal stator shape design for the IPM motor satisfying both improved torque performance and geometrical simplification for manufacturing. To control the geometrical complexity, the concepts of the phase-field model and the level-set method are employed. The optimization problem is formulated to minimize two values: the first is the torque ripple done by adjusting the torque values at any rotor position to constant target torque, and the second is the fictitious interface energy of the phase-field model as it narrows the interfacial region. The proposed method is applied to the structural stator design of a 12-pole 18-slot IPM motor developed as a power source for hybrid electric vehicles.

Influence of Slot Opening on Optimal Stator and Rotor Pole Combination and Electromagnetic Performance of Switched-Flux PM Brushless AC Machines

The significant influence of slot opening on the optimal stator and rotor pole combination and on the electromagnetic performance of the switched-flux permanent magnet (SFPM) machine is observed and investigated in this paper. A new SFPM brushless machine with remarkable slot opening relative to the magnet thickness is developed to reduce the magnet usage and to increase the slot area. Its stator slot opening is almost several times of that in the conventional SFPM machine, but its magnet usage is only half. However, the new machine exhibits ~ 40% larger back EMF and electromagnetic torque than those of the conventional machine, while its cogging torque and torque ripple are significantly lower.

Variable Structure Fuzzy-PID Control for DFIG System

In order to most effectively utilize the wind energy and improve the eficiency of wind generation system，an optimum control strategy of doublyfed induction generators (DFIG) was proposed,which made the system operationfor both the maximum wind enemy captured below the rated wind speed．Based on the wind turbine characteristics and basic electromagnetic relationship of DFIG the mathematical models of the stator active power and reactive power of DFIG were derived to fulfill maximal wind energy capture and conversion．A dual-passage excitation fuzzy control strategy based on dynamic synchronous reference frame was applied to control the proposed optimal stator active and reactive power．The operational performan ces of the wind turbine system with DFIG with wind speed variation were analyzed an d compared by using Matlab/Simulink．The results show the correctness and feasibility of the proposed control strategy.

Three-Phase Induction Motor Stator Current Optimization

This research presents two mathematical –based optimal control systems for induction motor drives leading to stator current optimization and energy saving. The first is a classical optimal control system, which uses information on torque of the motor to generate the appropriate voltage amplitude that minimizes the induction motor stator current. The second is a genetic algorithmbased optimal control system, which uses information on torque of the motor to generate the appropriate minimum stator current according to fitness function. The constant f V optimal stator current controller models have been configured and built depending on a set of experimental data using MATLAB computer program, the models were validated by simulation using a typical induction motor drive model implemented with MATLAB/Simulink toolbox. The aim of this research is the industrial machineries performance improvement by analyzing and designing the induction motor optimal stator current controller, this will minimize the stator current under different loading conditions. Depending on the motor shaft mechanical load torque in order to minimize the stator current, the controller will supply stator of motor with proper voltage and frequency using appropriate control algorithm for industrial machinery. General Terms Algorithms, Performance, Experimentation

Optimal Stator Design of Interior Permanent Magnet Motor to Reduce Torque Ripple Using the Level Set Method

Interior permanent magnet (IPM) motor is widely used for many industrial applications and has relatively high torque ripple generated by reluctance torque which results in noise and vibration. Since the configuration of the stator has great influence on reluctance torque, design optimization is necessary to improve the torque performance of IPM motor. In this paper, structural optimization based on the level set method is formulated to reduce torque ripples by minimizing the difference between torque values at defined rotor positions and the constant target average torque value under the constrained material usage. The nonlinear ferromagnetic material boundary of the stator is implicitly represented through an embedded level set function and the movement of the material boundary is driven by the normal velocity derived from optimality and convergence conditions of the level set equation. The proposed method is applied to design the optimal stator configurations of a traction motor of hybrid electric vehicle and presents the improved torque characteristics of IPM motor.

Starting the Single-Phase Switched Reluctance Motor Using Rotor Shorting Rings

This article presents a technique that uses rotor shorting rings to start the single-phase switched reluctance (SR) machine, from any rotor position, in a specified direction. It also outlines how the shorting rings enable starting of the machine. Transient finite-element analysis is used to illustrate the torque-producing mechanism from the aligned position using the rotor-mounted shorting rings. It is also used to determine the optimal stator and rotor pole arcs and shorting ring design for a 200-W prototype machine. An SR drive system incorporating rotor shorting rings is evaluated, and experimental results show the effectiveness of the technique

Torque ripple reduction in exterior-rotor permanent magnet synchronous motor

The paper presents torque ripple reduction in permanent magnet synchronous motor with exterior-rotor. The influence of the magnet pole arc width and the influence of the supply current waveform on the torque ripple are considered in the analysis. The results of the analysis are obtained by the finite element method simulation and are verified experimentally as well. The reduction of total torque ripple at nominal load conditions less than 2% is achieved by proper motor magnet pole arc design and by applying the optimal stator current waveform control.

Optimal stator slot design of inverter-fed induction motor in consideration of harmonic losses

This paper proposes optimal design method of stator slot for three-phase cage induction motor fed by six-step inverter output voltage by using proposed analysis method. The finite-element method (FEM) on one phase band stator periodic condition is coupled with harmonic equivalent circuit. Using the FEM, the stator slot is optimally designed and the result is presented. Stator core loss and copper loss including harmonic loss are reduced by the proposed optimum slot design method. The analysis result is verified by experimental measurement.