Conventional Rotor Research Articles

Design of a 35 kW Permanent Magnet Synchronous Motor for Electric Vehicle Equipped With Non-Uniform Air Gap Rotor

This article presents a successful design of a 35kW U-shaped interior permanent magnet synchronous motor (IPMSM) developed for electric vehicles. An improved rotor with non-uniform periphery based on the eccentricity principle is adopted to make the minimum air gap length appear on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis and the maximum on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis, thereby improving electromagnetic performance characteristics. Starting from the influence coefficient of this non-uniform air gap, a no-load air gap magnetic field analysis method based on magnetic potential permeance method is established. Afterwards, a two-segment Taguchi optimization model coupled with variable interaction analysis is innovatively proposed. This model optimizes non-uniform rotor periphery and other crucial dimensions for further performance improvement. The effectiveness of this no-load magnetic field analysis method is validated by a series of prototype tests and simulation results. Many simulation analyses of finite element method (FEM) and computational fluid dynamics highlight advantages of the designed IPMSM by comparing its performance indexes with those of the IPMSM with conventional rotor. Simultaneously, the advanced nature and rationality of improved optimization model is also well proven. In addition, operational reliability evaluation including demagnetization and mechanical strength is also implemented to verify the rationality of this design.

Functionally integrated additive manufactured rotor components for torque-dense aircraft electric motors

In dealing with emissions targets worldwide, fundamental questions about the future arise for commercial aviation. The resulting consequences for aviation require efforts to make air traffic CO2 neutral. In this context, electrification is an important building block to enable the aviation industry to provide transport in the future with increasing traffic volumes. To achieve this goal, electric motors for flight operation must have a high power and torque density and operate as energy-efficiently as possible. The PM synchronous motors predominantly proposed for such applications have above average efficiencies but could provide higher peak powers if they could be thermally more loaded. In particular, the sensitive permanent magnets lose efficiency as the operating temperature of the electric motor increases, reducing the maximum possible torque of the motor. Since conventional rotor construction methods limit the design, additive manufacturing is used to develop a rotor design that allows the rotor magnets to be cooled in close range to their contours. In addition, by selective laser melting mechanical, thermal, and magnetic functions are integrated. A process for hybrid manufacturing of novel rotor topologies is proposed. For this purpose, the rather conventional rotor topology is replaced by an additive function-integrated component for a reference electric motor. By means of an FEM analysis, it was shown that the mechanical strength of the alternative fixation method is maintained. Using adequate design guidelines, the AM structural components were fabricated in aluminum and an iron-nickel alloy and the permanent magnets were secured on it using 1K-epoxy adhesive. CFD analysis was used to simulate the flow conditions and heat transfer to the coolant in the internal structures of the AM components. Finally, the effect of the integrated cooling function was verified with an experimental setup. The results show that the torque influencing factor of the magnetic induction can be increased.

Performance Improvement of Induction Motor Controlled by Thyristor Chopper on the Rotor Side

In this paper, the performance characteristics of a variable-speed drive system with a wound rotor induction motor incorporating a 3-phase diode bridge rectifier - thyristor chopper with a modified commutation circuit system on the rotor side were studied. A DC equivalent circuit was used in the analysis of the motor-rectifier-chopper system and suitable equations have been derived for the determination of the system performance. The analytical results obtained are compared with those obtained experimentally to ascertain the validity of the system in practical applications. The results obtained indicate that a true variable speed drive system based on a thyristor chopper-controlled induction motor is successfully implemented. It is shown that the thyristor chopper control using the Hitachi commutation circuit permits the realization of a slip-ring induction motor as a variable speed and improved power factor. Also, the torque level obtained by the chopper control was found to be three times that obtained from conventional rotor resistance control at the same conditions.

MTPA Tracking Control of Sensorless IPMSM Based on Square-Wave Voltage Signal Injection

This article proposes an online maximum torque-per-Ampere (MTPA) control of an interior permanent-magnet synchronous motor (IPMSM) based on the square-wave voltage signal injection. Because the proposed method does not rely on a position sensor, it is applicable to sensorless IPMSMs. The proposed algorithm consists of a dynamic inductance estimator, frequency-adaptive flux observer, and an MTPA tracking controller. The proposed inductance estimation utilizes the pulsating square-wave voltage injection, which can maximize the injection frequency, and the dynamic performance can be preserved during the signal injection. Through the online flux and inductance estimation, the magnetic saturation of the IPMSM and the temperature variation can be fully considered in the MTPA control. The conventional rotor position estimator is replaced with the MTPA tracking controller, which does not rely on offline commissioning parameters. The proposed algorithm can operate under both the torque control and speed control mode, and accurate torque control on MTPA curve can be achieved. The simulation and experimental results demonstrate that the proposed method accurately tracks the MTPA point up to 200% of the rated torque in the mid- and high-speed region.

A new rotor structural design method of rotating packed bed based on hydrodynamic performance analysis

The rotating packed bed (RPB) is a typical process intensification device. However, the unbalanced vibration of the rotor makes the rotor transmission shaft squeeze the bearing and shaft seal frequently, which may destroy the bearing and shaft seal and cause material leakage. In response to this situation, this paper proposes a new spherical rotor structure design method based on hydrodynamic performance analysis for the RPB. It establishes the CFD models, including a conventional rotor structure and a spherical structure. The gas-liquid flow field characteristics in the two kinds of structural equipment are analyzed from the CFD results. It is found that the gas-liquid flow field distribution of the RPB with a spherical rotor structure is consistent with that of the conventional RPB, and the residence time of the liquid is less than 1s. The RPB with a spherical rotor structure meets the fluid performance of the high-gravity reactor. The gas-phase pressure drop of RPB with a spherical rotor structure is 20−35% lower than conventional structural RPB, and it increases the liquid holdup by 30−50%. It can be concluded that RPB with a spherical rotor structure has the advantages of lower pressure drop and higher liquid capture ability.

IF 기동방식 센서리스 압축기의 소음 및 진동 저감 제어

This paper presents a simple mechanical vibration and acoustic noise reduction of IF(current-frequency) starting sensorless controlled compressor. The adopted compressor is controlled by the sensorless estimation using back EMF observer in the normal speed range. In order to increase the speed up to normal sensorless speed range, the IF open-loop starting method is used. At the IF starting, the speed variation from the fluid load makes a mechanical vibration and acoustic noise. In order to reduce the mechanical vibration and acoustic noise, a simple variable torque slope with initial rotor position estimation method is proposed in this paper. The proposed method uses an initial rotor position estimation than a conventional rotor alignment method. And, the torque reference slope according to the increased open-loop speed is changed by the hysteresis error between the open-loop reference speed and the estimated speed. Because of the initial rotor position and the variable current according to the speed can reduce the collision of the compressor at standstill and low-speed region. Consequently the mechanical vibration and acoustic noise can be reduced.BRThe proposed simple variable IF starting method is verified 2.2kW IPMSM driven HVAC(Heating, Ventilation & Air conditioning) compressor. Experimental results shows the reduced vibration and acoustic noise at the starting to normal speed range.

End-Ring Wear in Deep-Well Submersible Motor Pumps

Wear of end ring is to date an unreported and uninvestigated failure that very frequently takes place in deep-well submersible motor pumps. This article first analyses the particularities of these induction motors, especially their unusual rotor manufacturing process. Failure mechanism related to the end-ring wear is described, showing several examples of damaged rotors in a motor repair shop. Then, the difficulties of its diagnosis through conventional rotor asymmetry indicators are described, caused by the subtlety of this fault and the very easy appearance of false negatives. The end-ring wear detection through a multicomponent approach is researched through simulation, laboratory results, and the diagnosis of two-field motors showing that new fault alarm levels need to be defined. To perform this last step and for the first time in the technical literature, two induction motors working in a deep borehole have been continuously monitored (one measure every six operating hours) for almost one year.

Brushless Wound Rotor Synchronous Machine Based on a Consequent-Pole Rotor Structure with Better Torque Attributes

This paper presents a subharmonic-based brushless wound rotor synchronous machine (BL-WRSM) topology with permanent magnet-assisted (PMA) and consequent-pole (CP) rotor structures to achieve better torque characteristics as compared to the conventional subharmonic-based brushless WRSM. The proposed topologies use the conventional high-efficient subharmonic field excitation technique to achieve a brushless operation and a lower volume of permanent magnet (PM) to achieve better average, starting, maximum, and minimum torques and lower torque ripple. A four-pole, twenty-four-slot (4-pole/24-slot) machine with conventional, PM-assisted (PMA), and consequent-pole (CP) rotor structures are developed in a JMAG-Designer 20.1 environment to carry out two-dimensional finite element analysis (2D-FEA). The developed machines are used to validate the operation and achieve electromagnetic and electromechanical performances of the proposed subharmonic-based BL-WRSM topologies with better torque attributes.

Numerical prediction of improvement of a Savonius rotor performance with curtaining and fin addition on blade

Savonius turbine is a vertical axis wind turbine (VAWT) which is suitable to operate at low wind velocities. The experimental investigation to improve its performance is a big challenge as; it is expensive, complicating and time consuming. Numerical prediction using CFD simulation could be a valuable alternative. This paper introduces a new modification of Savonius wind rotors to improve its performance. The proposed modification consists of a curtain arrangement together with fin addition on blade. The effect of the proposed modification was predicted using a CFD simulation employing ‘ANSYS FLUENT 16′. The curtain arrangement was located in front of the rotor to avoid the opposing torque to the rotor rotation. The fins were added to exploit the space in the blade for guiding the wind flow. The performance of the rotor with different curtain arrangements and variable number of fins was predicted and assessed against that of the conventional rotor. This comparison aimed to optimize the geometrical data of the proposed curtain arrangement with the number of added fins. The maximum power coefficient of the Savonius wind rotor was found to be increased to about 42 % with the optimum curtain arrangement (lengths of the curtain blades 1000 and 1150 mm and the angles of the curtain blades 30 and 50) together with adding only one fin. The simulation results showed that the performance of Savonius wind rotors could be significantly enhanced with a proper selection of curtain arrangement and number of fins to be added on the blade.

Response of a Tandem-Staged Compressor to Circumferential Inflow Distortion

Abstract Tandem rotor, as a concept, promises a higher diffusion capacity than a single rotor. However, it is reported to have a lower operating range than the conventional rotor. Inflow distortion can lead to significant changes in the flow dynamics of the axial-flow compressor. Further, a highly loaded tandem blade is likely to be severely affected due to the inflow distortions. In this study, circumferential distortion is imposed at the inlet of a tandem stage and its response is studied, using steady and unsteady probes. The performance characteristics and other aerodynamics parameters under the circumferential distortion are compared with the clean inflow case. As expected, the tandem stage experiences a significant drop in the total pressure rise and operating range under circumferential distortion. A large deficit in the total pressure, efficiency, and axial velocity is observed in the distorted region. The casing pressure traces, Morlet wavelet analysis, and Fast Fourier Transform techniques are used to analyze the unsteady data. The stall is incepted in the form of a low-intensity spike, which later evolved into a fully grown stall within 2.5 rotor revolutions. Further, the amplitude of the stall cell under the circumferential distortion is found to be higher than the clean flow.

Modified Savonius Wind Turbine for Wind Energy Harvesting in Urban Environments

Abstract The flow-induced rotation of the modified Savonius rotor, for which the blade consists of a semicircular profile and an elliptical shape, is studied using a series of unsteady computational fluid dynamics (CFD) simulations. This study first concentrates on the validation of the numerical scheme against Blackwell's experimental data of the conventional rotor. The computed flow physics around the modified rotor with the same diameter is then analyzed and compared with that of the conventional rotor during one rotation cycle. As the result, the modified rotor is outperforming the conventional one but keeping its unique features. The modified rotor offers exceeding performance at a tip speed ratio (TSR) greater than 0.8. The new peak of the power coefficient Cp is reached at TSR = 1.4 which is a typical operating condition of the wind turbine in urban areas. The remarkable finding is that the suppression of the flow separation on the blade is an effective way to improve the rotor's aerodynamic performance. As expected, the additional elliptical profile plays a key role in increasing the positive torque and in preventing the flow separation on the blade, especially at high TSR &amp;gt; 0.8. Finally, this study points to not only advances the fundamental understanding of flow mechanism around the rotor but also proposes a good practical energy harvesting application in urban environments.

Feature extraction from multi-axis MEMS sensors for unbalance detection in non-stationary rotating conditions

Conventional rotor balancers are driven by electric motors that maintain the machine rotor/shaft assembly at a constant rotational speed throughout the whole unbalance detection process. The present work expands the operating field of balancing machines, providing an algorithm enabling rotor balancing in non-stationary coasting-down regions, i.e., during the deceleration phase of the rotor/shaft assembly. In this context, the action of the electric motor, or of any other actuator, is just needed to bring the rotor/shaft assembly at the initial target rotational speed, reducing the overall energy consumption. Then, the actuator is deactivated and the unbalance is detected while the rotating mass is decelerating freely. The effectiveness of the proposed unbalance detection algorithm is proven over the case study of a human-powered wheel balancer. The proposed strategy allows the effective detection of static unbalanced masses higher than or equal to 20g considering both 15′′ and 16′′ vehicle wheels.

Identification of Bearing Dynamic Parameters and Unbalanced Forces in a Flexible Rotor System Supported by Oil-Film Bearings and Active Magnetic Devices

As the rotational speed of conventional rotor systems supported by oil-film bearings has increased, vibration problems such as oil whip and oil whirl have become apparent. Our group proposed the use of active magnetic bearings (AMBs)/bearingless motors (BELMs) to stabilize these systems. In such a system, measuring the variable stiffness and damping of the oil-film bearings, the current-force and displacement-force parameters of the AMBs/BELMs, and the residual unbalanced force is necessary to satisfy the stability of the rotor system. These parameters are the foundation for the rotor dynamics analysis and optimization of the control strategy. In this paper, we propose a method to simultaneously identify the parameters of the oil-film bearings and AMBs/BELMs along with the residual unbalanced forces during the unbalanced vibration of the rotor. The proposed method requires independent rotor responses and control currents to form a regression equation to estimate all the unknown parameters. Independent rotor responses are realized by changing the PID control parameters of the AMBs/BELMs. Numerical simulation results show that the proposed method is highly accurate and has good robustness to measurement noise. The experimental results show that the unknown parameters identified by the responses generated by different controller parameters are similar. To confirm that the identification results are correct, verification experiments were carried out. The vibration amplitude of the rotor was successfully suppressed by applying a force to the rotor in the opposite direction to the residual unbalanced force. The frequency response characteristics and unbalanced responses of the rotor estimated by the values of the parameters identified show good consistency with the measured results.

Numerical Study of Porous Media Effect on the Blade Surface of Vertical Axis Wind Turbine for Enhancement of Aerodynamic Performance

This paper discusses the novel design of VAWT by employing porous media on turbine blades. 2D simulation was performed with CFD package Star CCM to observe flow behavior around VAWT blades. DU 06-W-200 airfoil with six porous configurations including both the pressure and suction side of airfoil have been investigated to obtain optimum porous location. The aerodynamic coefficients of these configurations have been calculated and compared with that of the conventional blade for the broad range of angle of attack. It is found that porous media on the pressure side of airfoil behave more effectively and increase the CL/CD values. Then three straight blade Darrieus type rotor performance in presence of porous media has been studied. The results reveal the enhancement of power and torque coefficient in a range including both before and after optimum tip speed ratio. Therefore, the turbine self-starting capability improves and consequently, it starts operating at low wind speed which leads to the reduction of VAWT cut-in and increases annual energy production. Additionally, the blade equipped with porous media experience a higher stall angle of attack and is able to exceed the maximum azimuth angle of the conventional rotor. Hence, stall phenomena delay and occurs at a higher angle of attack. The main reason for these improvements is related to the capability of porous media to attach the flow on blade profile and suppress separation zone.

Impact of renewable generation on probabilistic dynamic security assessment of a power transmission system

ABSTRACT Dynamic security assessment (DSA) is a vital part of power system planning and operation. Although various phenomena, such as line thermal loading, voltage stability, and frequency stability, are of interest in DSA, this paper particularly focuses on transient rotor angle stability of conventional synchronous generators in a transmission system. Integration of large wind and photovoltaic (PV) farms to the bulk power systems has brought various challenges to the conventional rotor angle transient stability of synchronous generators. It is, therefore, of immense importance to examine and comprehend the impact of various renewable generations and their penetration levels on the probabilistic transient stability. This paper uses time-domain simulation approach to analyse these impacts in terms of probability of system instability, based on the transient stability index (TSI). Various case studies are conducted on the IEEE 39-bus test system, considering the probabilistic nature of parameters (faulted line/bus, fault type, fault location, and fault duration). The results obtained indicate that hybrid renewable energy integration is the best choice for achieving the highest probabilistic dynamic security, considering (N-1) and (N-2) line and (N-1) bus faults.

Experimental and numerical studies on small contra-rotating electrical ducted fan engines

Electrical propulsion has been identified as one of the key fields of future research within the aerospace sector. The Institute of Aeronautical Engineering at the Universität der Bundeswehr München aims to contribute to the ongoing development of small-sized electrical ducted fan engines with a thrust in the range of 100 N. A special emphasis is placed on electrically powered contra-rotating fan stages. When compared to a conventional rotor–stator stage, contra-rotating fan stages allow for a more compact design, considering a given pressure ratio, or an increased pressure ratio at a constant fan diameter. Since numerous new aircraft concepts are presently being developed, a high demand for compact and powerful electrically driven engines arises. Electrically driven contra-rotating fan engines provide a high potential in terms of compactness, emissions and efficiency. Using electric motors offers the ability to overcome common issues, such as design and integration of a contra-rotating stage into a gas turbine. An innovative new engine design featuring such a contra-rotating stage is developed and tested at one of the Institute’s test benches for electrical propulsion. Key components are two brushless motors powering the fan stage, one for each rotor. Various operation points are investigated experimentally during an extensive test campaign. Experimental results are compared to results of numerical simulations computed by ANSYS CFX. Results indicate a good agreement between experiment and simulation. The engine is running very smooth throughout all tested operation points. Yet, intensive heating up of the electric motors and high-temperature zone are found to be an issue at higher rotation speeds.

Impact of optimized variable rotor speed and active blade twist control on helicopter blade–vortex interaction noise and environmental impact

Combined variable rotor speed and active blade twist helicopter technologies have the potential to reduce the environmental and acoustic impact of modern rotorcraft. This paper explores the aeroacoustics, environmental and ground noise impact of combined variable rotor speed and active blade twist helicopter rotors, optimized for simultaneous mitigation of source noise and NOx emissions. An integrated approach is employed including free-wake aeroelastic rotor modeling and time-domain aeroacoustic formulations fundamentally based on Acoustic Analogy. The overall method is incorporated into a multi-disciplinary design space exploration and surrogate-model-assisted optimization algorithm. The developed framework is deployed towards devising optimal variable rotor speed and active blade twist control for a representative twin-engine light helicopter operating in a realistic descent trajectory. The obtained rotor control schedules achieve overall ground noise reductions of up to 7 dB with concurrent NOx reductions of 11%, relative to the conventional rotor. The proposed approach provides new insight into rotor wake behavior and blade–vortex interactions, as well as environmental impact and ground noise footprint of combined variable rotor speed and active blade twist helicopter concepts.

Load Test and Efficiency Map Measurement of 50 kW Class Induction/Synchronous Superconducting Machine (HTS-ISM)

The operation of an electric machine in electric vehicles (EV) needs to be very efficient. In that goal, this work investigates an induction machine where the conventional rotor conductors are replaced by superconductors. The resulted machine is partially superconducting, but the use of superconductors on the rotor will induce an unconventional behavior. Indeed, a synchronous operation is possible with some trapped current due to the zero resistivity of the superconductors, enhancing also the overall efficiency of the machine. After a presentation of the experimental setup, the efficiency map is calculated in two different ways. Both results are obtained from experimental data.

Comparative Study of a Conventional, Coaxial Counter-Rotating, and Co-Rotating Rotor Aerodynamics in Hover

Comparative Study of a Conventional, Coaxial Counter-Rotating, and Co-Rotating Rotor Aerodynamics in Hover

Customized shape optimization of switched reluctance motor using B-Splines

PurposeThis study aims to design the rotor geometry of switched reluctance motor (SRM) in a completely flexible way. In the proposed method, there is no default geometry for the rotor. The initial geometry of the rotor can start from a circle or any other shape and depending on the required performance takes the final shape during the optimal design. In this way, the best performance, possible with geometric design, can be achieved.Design/methodology/approachThe rotor boundary of a 4/2 SRM is defined by a few B-splines. Some control points are located around the rotor and changing their locations causes customized changes in the rotor boundary. Locations of these points are defined as design variables. A 2-D finite element analysis using MATLAB/PDE is applied to the SRM model and sensitivity analysis is used to optimization design by means of minimizing of objective function.FindingsThe proposed method has many more capabilities for matching different objective functions. For the suggested objective function, while the conventional rotor torque profile difference with the desired torque profile reaches 40%, this difference for B-spline rotor is about 17%. Experimental results from a prototype motor have a close agreement with analysis results.Originality/valueThe B-splines have been used to design machines and electromagnetic devices. However, this method is used for the first time in design of the whole rotor of a SRM.