Rotor Slot Research Articles

Study on fluid flow as well as heat transfer characteristics of high-speed solid-rotor motor cooled by natural gas based on turbulent Taylor-Couette vortex

The High-speed Solid-rotor Induction Motor Cooled by Natural Gas (HSIMCNG), is suitable for integrated compressors in natural gas pipeline transportation due to its high mechanical strength. In order to further improve the cooling effect of the motor and lighten the motor weight, it is of great significance to research on the natural gas flow, heat transfer characteristics and motor structure optimization. Firstly, the natural gas flow state characteristics in the 160 kW HSIMCNG are investigated in this article. The natural gas Taylor vortex distribution in the air gap is analyzed, and the natural gas flow as well as heat transfer characteristics are obtained. Secondly, in the cooling structure of the motor with slotted rotor, the impact of the slot on the natural gas flow state is further explored in detail by combining the mechanism of the Taylor vortex on the natural gas turbulent kinetic energy, and the natural gas heat transfer effect is clarified. Finally, the variation characteristics of the natural gas radial and tangential velocities with the spatial position in the motor with different ventilation cooling structures are compared and analyzed in depth, and the key factors affecting the natural gas Taylor vortex flow and heat transfer effect are determined.

Design and analysis of electromagnetic and mechanical structure of ultra-high-speed slotted solid rotor induction motor

In this paper, a high speed slotted solid-rotor induction motor (SSRIM) with rated power of 15 kW and rated speed of 120krpm is studied, and its electromagnetic performance and rotor mechanical structure are optimized. First, according to the empirical formula of motor design, the volume size of the motor is determined. Then, by constructing a two-dimensional finite element model, the slot matching scheme and coil pitch are optimized, and the influence of different slot matching scheme and coil pitch on the output torque and harmonics of the motor is compared. Then, the influence of rotor slot size on electromagnetic and mechanical properties of the motor is described in detail. Finally, a finite element model is constructed to verify the mechanical strength of the rotor, and the influence of temperature on the deformation and stress of the rotor is explored. Through the analysis, it is found that the slot matching scheme has a great influence on the torque ripple of the motor, and the torque ripple can be reduced by selecting the slot matching scheme reasonably. Secondly, the size of the rotor slot has a great impact on the electromagnetic and mechanical properties of the motor, and it is necessary to comprehensively consider and jointly optimize its size.

Analytical Study on the Effect of Rotor Slot Skewing on the Parasitic Torques of the Squirrel Cage Induction Machine

Analytical Study on the Effect of Rotor Slot Skewing on the Parasitic Torques of the Squirrel Cage Induction Machine

Mechanism investigation of stability enhancement by slot on a transonic compressor

Abstract As aircraft engine blades develop towards high loads and low aspect ratios, the flow conditions in the tip region of transonic compressor rotors become more complex. The interaction between shock waves and boundary layers tends to induce fluid separation, thereby reducing the stable operating range of the rotor. To enhance the stability margin of the rotor, this study employs numerical simulation techniques to design jet slots on the rotor 37. Research results show that, without compromising the performance of the rotor, the slotted rotor can effectively enhance the stability margin of the rotor at both design and off-design speeds, with increases of 60.9% and 47.9% in surge margins compared to the prototype.

Modeling of Induction Motor Direct Starting with and without Considering Current Displacement in Slot

This article presents a mathematical model of three-phase induction motor (IM) with a squirrel cage rotor and investigates its starting modes. Specifically, two scenarios are considered: direct starting of an IM and direct starting considering the current displacement effect in the rotor slots. Analyzing the starting modes of an IM without the use of automatic control systems is crucial for ensuring reliable, efficient, and safe operation of equipment across various industrial and commercial sectors. Understanding and accounting for the processes occurring during the starting mode of an IM allows for minimizing risks, enhancing energy efficiency, and reducing operational costs. This article details the mathematical modeling methods used for analyzing these starting modes and the results obtained from the modeling. These results were compared with data obtained experimentally, allowing for the assessment of the accuracy and reliability of the proposed model. The conducted research highlights the importance of considering current displacement in the rotor slots for accurate modeling and analysis of induction motor starting modes, particularly in capturing the differences in the amplitudes of the starting current and the faster transition to steady-state operation. Conclusions drawn from the comparison of modeling and experimental data provide valuable insights for the further development of control and operation methods for induction motors.

Concurrent and sequential coupled optimization design of a transonic compressor blade with axial slot casing treatment

This paper explores the optimization of the interaction between the rotor and axial slot casing treatment (ASCT) to enhance both efficiency and stability margins. Previous studies primarily focused on rotor tip optimization, often compromising flow in non-tip regions and reducing overall rotor performance. To address these limitations, this study introduces a new optimization framework integrating full-span 3D blade design with a semicircular axial slot, utilizing both sequential and concurrent optimization strategies. The sequential approach first optimizes blade geometries, followed by ASCT adjustments, while the concurrent approach treats the blade and ASCT as a unified aerodynamic system. Compared to prior studies focusing exclusively on tip-only 3D shape optimization, results indicate that sequential coupled optimization improves the stall margin by 13.32% and efficiency by 0.05%, whereas the concurrent strategy further enhances performance, shaping the blades into an inverse S form, reducing efficiency losses from 0.12% to 0.02%, and increasing the stall margin increment from 14.88% to 21.83%. These findings demonstrate the significant performance gains achievable through coordinated rotor and ASCT design.

Analytical prediction of the open‐circuit magnetic field for the V‐shaped interior PM machine by the improved subdomain method

AbstractThe open‐circuit magnetic field of the V‐shaped interior PM (IPM) machine is predicted by the analytical method. The method is implemented following the basic principle of the subdomain method. The machine model is divided into five different regions, including rotor slot, magnetic barrier, air gap, stator slot, and stator slot opening. To perform the analytical prediction process in the polar coordinate system, these regions should be transformed into the appropriate subdomains. The last four regions can be transformed into the subdomains with the required shape based on the existing method. The rotor slot cannot be treated as a single subdomain, for the shape of which is irregular. Herein, the PM and vacuum region in the rotor slot is divided into several fan‐shaped subdomains. The division method is described clearly. Then, the boundary conditions alongside the interface between adjacent subdomains are derived based on function transformation. On this basis, the open‐circuit magnetic field of the IPM machine can be predicted. The magnetic field of the 6p/36 s V‐shaped IPM machine is obtained by the proposed method, finite element method simulation, and experiment, respectively. Additionally, the comparison results verify the accuracy and efficiency of the proposed method.

Analysis and Suppression of Spoke-Type Permanent Magnet Machines Cogging Torque with Different Conditions for Electric Vehicles

Spoke-type permanent magnet (STPM) machines have high power density and low cost due to flux concentrated effect and high air-gap flux density, but they can cause high cogging torque and torque ripple. To reduce the cogging torque, the analytical model considering a rotor slot is established and compared with the finite element mothed (FEM). Then, the cogging torque production mechanism is revealed and analyzed under different conditions, which provides direction to optimize the cogging torque STPM machines. The harmonic content of cogging torque under different conditions is obtained based on the freezing permeability (FP) method. It is found that the fundamental waves mainly generate the cogging torque under a no-load condition, and it is mainly generated by the second harmonics under an on-load condition. In addition, the optimization method is introduced and researched, including rotor slot width, uneven rotor core, and so on. Finally, a 50 kW STPM machine prototype is manufactured and tested to verify the accuracy and efficiency of the analysis method.

Study of an Asynchronous Traction Motor with Inclined Slot Rotor

Study of an Asynchronous Traction Motor with Inclined Slot Rotor

Cogging torque reduction by utilizing the unequal rotor slot arc method for FSPM Machines

Cogging torque is a crucial and offending problem for electric machines that consist permanent magnets. Flux switching permanent magnet (FSPM) machines have magnets embedded inside the stator coils. Due to the interaction between the stator magnetic flux and the rotor steel, cogging torque occurs. To express this interaction, Magnetic Permeance Distribution Model is implemented in this study. To minimize the cogging torque, unequal rotor slot arc (URSA) technique is developed and cogging torque is calculated by using finite element method. An optimization study is performed to get the minimum value of the cogging torque under reasonable output torque. Results prove that, the proposed URSA method have promising outcomes for cogging torque reduction.

Design and experimental verification of hybrid excitation magnetic field modulation machine for electric vehicle propulsion

As one sort of flux modulation machine based on magnetic gear effect, field-modulated machine features with low speed large torque. A novel hybrid excitation field-modulated machine (HEFMM) is proposed by introducing the concept of hybrid excitation, the flux modulation poles (FMPs) and excitation winding of which are emplaced in stator teeth and the adjacent FMPs. It can be maintained wide speed range operation through the processes of flux-enhancing and flux-weakening with no increasing machine bulk, as well as the numbers of stator and rotor slot. The working principle of proposed machine is deeply studied, as well as basic electromagnetic characteristics are calculated by finite element method, including no-load magnetic flux linkage, no-load back electromotive force, cogging torque and output torque. In addition, the processes of flux-enhancing and flux-weakening are analyzed. Finally, one prototype with one kilowatt was built and its static characteristics were tested. The results show that the proposed HEFMM has the features of high torque density, small cogging torque and wide speed range, which is promising candidate for electric vehicle direct drive field.

Selection of induction motor stator and rotor slot number combination for optimal NVH

With the rise of vehicle electrification, considerable research has been directed towards reducing motor noise, predominantly focusing on Permanent Magnet Synchronous Motors (PMSM). Despite the increasing popularity of the induction motor, driven by its reliability, cost-effectiveness, and lower environmental impact, discussions surrounding the Noise, Vibration, and Harshness (NVH) aspects of induction motors remain limited. This paper addresses the NVH implications associated with stator and rotor slot combinations in conventional squirrel-cage induction motors. Through a design parametric study that examines the impact of varying the number of rotor bars through analytical simulation, the findings not only identify the optimal slot combination for minimizing motor noise but also demonstrate the critical importance of selecting the proper slot configuration, as NVH performance can exhibit significant variations. A physical test was conducted to validate the analytical simulations. This research contributes valuable insights into the induction motor design, especially at the early design stage, emphasizing the necessity of considerations in achieving enhanced NVH performance.

A Novel Rotor Harmonic Winding Configuration for the Brushless Wound Rotor Synchronous Machine

In the last decade, permanent magnet (PM)-free or hybrid PM machines have been extensively researched to find an alternative for high cost rare-earth PM machines. Brushless wound rotor synchronous machines (BL-WRSMs) are one of the alternatives to these PM machines. BL-WRSMs have a lower torque density compared to PM machines. In this paper, a new topology is introduced to improve the torque producing capability of the existing BL-WRSM by utilizing the vacant spaces in the rotor slots. The new topology has two harmonic windings placed on the rotor which induce separate currents. A capacitor is used between the two harmonic windings to bring the currents in phase with each other. The harmonic winding currents are fed to the rectifier which is also placed on the rotor. Due to additional harmonic winding, the overall field current fed to the rotor field winding has been increased and hence the average torque has also increased. Finite element analysis (FEA)-based simulations are performed using ANSYS Maxwell to validate the proposed topology. The results show that the average torque of the machine has been significantly increased compared to the reference model. The detailed comparison results are provided in this paper.

Rotor Flux and EEMF Observer for Interior Permanent Magnet Synchronous Machine

In recent years, the use of the Interior Permanent Magnet Synchronous Machine (IPMSM) in various applications has grown significantly due to numerous benefits. Sensors are used to achieve high efficiency and good dynamic response in IPMSM drives but due to their high cost and reduce overall size of system,sensorless control techniques are preferred. Non-sinusoidal distribution of rotor flux and slot harmonics are present in the considered IPMSM. In this article, these problems are considered as control system disturbances. With the above-mentioned problems, the classical observer structure based on (d-q) fails to estimate at low-speed ranges. This article proposes an observer structure based on a rotor flux vector in (α-β) stationary reference frame, which works using the adaptive control law to estimate speed and position, and a non-adaptive EEMF-based observer to estimate speed and position. Moreover, a comparative analysis between both observer structures at the different speed ranges is also considered in this article. The effectiveness of the observer structure is validated by simulation tests and experimental tests using the sensorless control system with a field-oriented control scheme for 3.5 kW IPMSM drive system.

Comparative analysis of harmonic sensitivity for stator fault diagnosis in induction motors

Induction motors play a vital role in various industrial applications due to their commendable efficiency and reliability. However, their susceptibility to faults, especially in challenging industrial environments, highlights the need for vigilant fault detection to prevent unforeseen downtimes and reduce subsequent repair costs. Early fault diagnosis is crucial in this context. A systematic approach to diagnosing faults in asynchronous motors involves the application of signal processing techniques, particularly utilizing the Fast Fourier Transform (FFT). The FFT, as a mathematical tool, enables a comprehensive analysis of signals, facilitating the identification and isolation of their frequency components. Monitoring the frequency components within a motor's signal provides a means to determine the existence and severity of faults. FFT analysis allows for the monitoring of four distinct categories of harmonics: time harmonics (TH), rotor slot harmonics (RSH), rotor bar fault harmonics (RBFH), and eccentricity fault harmonics (EFH). Each type of harmonic offers valuable insights into specific fault categories. Empirical evidence, drawn from experimental results, emphasizes the heightened sensitivity of rotor slot harmonics (RSH) in detecting stator faults. Continuous monitoring of the RSH frequency component enables the prompt detection and localization of stator faults, along with an assessment of their severity. Additionally, this diagnostic methodology proves effective in identifying micro short-circuits between stator coils, allowing for a proactive strategy in predictive maintenance. This proactive approach enables anticipatory part replacement before degradation progresses to the point of causing comprehensive failure in the production chain. The combination of FFT-based signal processing and harmonic analysis establishes a robust framework for the early detection and localization of faults in asynchronous motors within industrial settings. This contributes to enhanced operational reliability and efficiency, ultimately ensuring smoother industrial processes.

Integrated Design of Axial Slot Casing Treatment and Blades in a Low-Speed Single Stage Axial Compressor

Abstract Casing treatment has been used to enhance the stability of axial-flow compressor by extending the stall margin; it also induces strong interaction with compressor blades, as demonstrated in the open literature. Revealing the mechanism of this interaction is a key to fully exploit the potential of the stability-enhancing capability of casing treatment without efficiency penalty. For this purpose, an integrated optimization design of rotor and axial slot casing treatment is implemented for a low-speed axial-flow compressor, and the stall margin is increased by 10.89% without penalty on the peak efficiency. Through detailed analysis, two important driving factors for the improvement of stall margin are illustrated: the suction effect that decreases the axial momentum of tip leakage flow, and the injection effect that increases the axial momentum of main flow. Meanwhile, it is found that the combination of forward-deflection axial slot casing treatment and forward-sweep rotor can maximize the enhancement of the momentum exchange, thereby adequately reducing the blockage region induced by tip leakage flow. More specially, the stator is then redesigned based on the matching mechanism between the stator and rotor with axial slot casing treatment in a stage. This redesign can considerably reduce entropy generation and flow separation in the passage and achieve an improvement of 0.87% in efficiency. The results hence demonstrate the superiority of integrated design of axial slot casing treatment and blades in improving both stall margin and efficiency.

Speed Estimation of Induction Motor at Low and Zero Speed using High Frequency Signal Injection for Rotor Slot Harmonics Detection

Rotor position estimation based on high frequency signal injection method represents the interesting way to provide the high performances of the AC drives sensorless controlled at low or near zero speed range. So, this method requires the existence of saliencies inside the IM particularly the presence of the slots where their design constitutes the main advantageous to exploit its effect for rotor speed monitoring. First, the present paper exposes a model of the induction machine including slotting effects which it can be exploited in order to extract the harmonic saliency created by rotor slotting. Second, the high frequency signal injection method is used in order to allow tracking the characteristic harmonic saliency due to rotor slotting from which the rotor position and speed may be estimated. A High frequency voltage signal injection creates a high frequency current modulated by the saliencies presented inside the machine. To extract information about rotor position, the resulting stator current treads to heterodyning process to eliminate the disturbance components and subsequently the rotor position may be extracted by a closed-loop observer. Simulation results are shown in order to verify the validity of the proposal and to confirm the effectiveness of estimation method at zero frequency.

Diagnosis of Mixed Eccentricity in 400 kW Induction Machine Based on Inspection of Stator Current Spectrums

This paper dealing with diagnosis of induction machines affected by combined eccentricity via analyzing the sator curents, inspection of the current spectrums and predict the harmonics that present in the spectrums and represent an indication for this ailment . The machine under invistigation is a 400 kW, four pole-pair, squarelcage induction machine. The current spectrums were calculated for the cases of full symmetry and mixed eccentricity. The calculations presented in this paper, are based on the poly-harmonic model that accounting for static and dynamic eccentricity, stator and rotor slotting, parallel branches as well as cage asymmetry. The calculations were followed by Fourier analysis of the stator currents in steady state operation. The inspection of the current spectrums focusing on two main zones these are the 50 Hz fundamental harmonic zone and the main slot harmonic zone. The paper will include the zooms of the above mentioned zones to demonstrate the harmonics presented in each zone. The calculated spectrums will be compared with the spectrums of the real measured currents.

ANALISIS PERBANDINGAN DESAIN MOTOR INDUKSI 12 KW DENGAN MEMVARIASI JUMLAH SLOT PADA ROTOR

– The industry and transportation technology that continues to growing every year. The electric motor driven drive reduces the use of fossil fuels. Induction motors receive special attention in the general public because of their superior efficiency and compatibility compared to other types of motors, such as low cost, flexibility, easy to control. However, designers face difficulties in designing Induction Motors with high torque, power factor, efficiency and varying number of slots and rotors with special performance, high efficiency and better operational features. This study proposes choice of design type Induction Motors. The design process and analysis program use the Simcenter Motorsolve application. Design model for Induction Motor with output power 12 Kw 50 Hz. The design process focuses on the best analysis of the torque, efficiency, output power, and power factor of the induction motor, with a value of stator slot 24, rotor slot 24, 36, 48 in Simcenter Motorsolve. The performance of the designed motor is analyzed in conditions that are not good, good and very good. The results obtained using the Simcenter Motorsolve application show that the resulting design is accurate and effective.

Analysis of power loss in heat pipes for integrated thermal management of next generation electrical machines

This paper presents analysis of eddy-current power loss in heat pipes (HPs) for integrated thermal management of electrical machines. Here, a close integration of HPs with winding body is considered. Such an arrangement is particularly attractive, as it targets the main heat source within the machine assembly. However, there are several challenges associated with the subsystem compatibility, which include electromagnetic, thermal, and mechanical design aspects. The HP’s power loss, which is generated as a results of the time varying stator and/or rotor slot magnetic flux leakage, requires careful considerations. Although, the HP-enabled thermal management of electrical machines (electrical windings) has been previously investigated, the additional HP generated power loss has had a very little attention. In this work, the author proposes alternative techniques for accurate predictions of HP generated power loss accounting for the HP’s wick structure. Three alternative custom-built HP constructions Copper-Water and Titanium-Water with sintered and mesh wicks have been investigated in this analysis. Both theoretical finite element (FE) electromagnetic and experimental methods are discussed in detail. The results show that the proposed experiment informed FE model of HP with an equivalent electrical resistivity wick region provides an accurate HP representation useful in design of electrical machines. Further to these, the proposed approach is demonstrated on an example custom vapor chamber (VC) highlighting the importance of accurate power loss predictions in HPs and VCs.