Segmented Rotor Research Articles

Improved Design of Three Phase Hybrid Excitation Flux Switching Motor with Segmental Rotor

This paper presents the new design of Hybrid Excitation Flux Switching Motor (HEFSM) using segmental rotor structure. HEFSMs are those that consist all the excitation flux sources at their stator with robust rotor structure. The rotor is designed as segmental due to the reason that segmental rotor has ability to yield the magnetic path for conveying the field flux to nearby stator armature coil with respect to the rotation of the rotor. This design gives the clear advantage of shorter end winding compared to the toothed rotor as there is no overlap winding between field excitation coil (FEC) and armature coil. In this paper the initial design of HEFSM with segmental rotor has been improved by changing segment span, FEC slot area and armature slot area until maximum torque and power of 33.633 Nm and 8.17 KW respectively have been achieved. Moreover coil test analysis, induced voltage, cogging torque, magnetic flux characteristics, torque vs. field current density and torque vs. power speed characteristics are examined on the basis of 2-D finite element analysis (FEA).

Analysis, Optimization, and Prototyping of a Brushless DC Limited-Angle Torque-Motor With Segmented Rotor Pole Tip Structure

This paper presents the analysis and design of a two-pole dc brushless limited-angle torque-motor (LATM) with a toroidally wound armature using magnetic equivalent circuit modeling. A variety of design concepts is considered based on several defined criteria, and then, the most worthy alternative is chosen. To select the best design concept, an efficient decision-making tool called analytical hierarchy process is employed. A new segmented rotor pole tip structure of the LATM is introduced. The results obtained from finite-element simulation of the proposed machine conform well with the analysis. The selected design is prototyped, and the experimental results are presented.

Comparative Performance of FE-FSM, PM-FSM and HE-FSM with Segmental Rotor

Flux switching machines (FSMs), new type of electric machines with unique operating principles have been introduced and published recently. FSMs contain armature and excitation sources on the stator with robust rotor structure. According to rotor structure FSMs can be classified into two types namely salient pole rotor and segmental pole rotor. Various topologies have been studied and published using both rotor structures, however salient pole rotor has a demerit of less torque generation due to longer flux path resulting flux leakage surrounding the rotor. In this paper a new structure of hybrid excitation FSM (HEFSM) with segmental rotor is proposed and a comparative analysis with the invented field excitation FSM (FEFSM) and permanent magnet FSM (PMFSM) is presented. Initially, coil arrangement tests are examined to confirm the operating principle of HEFSM with segmental rotor. Moreover, the cogging torque, induced voltage, magnetic flux, torque at various armature current densities and power characteristics are observed based on 2D-finite element analysis (FEA).

Optimization of an 80-kW Segmental Rotor Switched Reluctance Machine for Automotive Traction

There is significant interest in the development of switched reluctance machines (SRMs) for use in automotive traction applications. This has been driven by their low cost compared with rare earth permanent-magnet-based motors, driven by the high cost of rare earth permanent magnets, coupled with their potential for competitive torque densities. This paper describes the development of a variant of the SRM, utilizing a segmental rotor construction, which has previously been demonstrated to provide the potential for significant improvement in torque densities compared with SRMs with a conventional toothed rotor construction. This paper describes a strategy that has been developed to optimize the Segmental Rotor SRM to maximize efficiency with the aim of achieving performance equivalent to that of the 80-kW interior permanent-magnet machine utilized in Nissan's LEAF electric vehicle. Optimization applies a combination of static and dynamic analyses in order to achieve a full and computationally efficient assessment of motor performance across different regions of the torque speed envelope. Test results from a prototype motor are also presented.

Design Methodology for High-Performance Segmented Rotor Switched Reluctance Motors

Switched reluctance motors (SRM) are becoming attractive due to the increasing cost of permanent magnets. It was reported that segmented rotor construction improves the torque output and efficiency of SRM. This paper investigates the effect of stator slot/rotor segment combination and number of phases on the performance of segmented rotor SRM (SSRM). It is found that SSRMs having higher number of rotor segments than stator slots have high efficiency and torque output, but they also have limitations of narrow speed range and low overload capability. On the other hand, it is found that SSRMs with higher number of both stator slots and rotor poles have high overload capability. The effect of increasing number of phases of SSRM is also evaluated. It is found that a polyphase SSRM improves the torque output, but does not have the limitations of low overload capability and narrow speed range. Thus, the choice of stator slot/rotor segment combination and number of phases depends largely on application. Procedure to select stator slot/rotor pole combination and number of phases of SSRM is presented here. Experimental results supporting conclusions from analysis are also given.

Performance Comparison and Analysis of (HEFSM) and (FEFSM) Using Segmental Rotor Structure

This paper presents a new structure of hybrid excitation flux switching motor (HEFSM) using segmental rotor and the comparison of HEFSM and FEFSM using segmental rotor is performed to find the best candidate for hybrid electric vehicles (HEV). (HEFSM) using segmental rotor contains both the FEC and PM on the stator to produce maximum flux linkages. Initially, the coil arrangement tests are examined to validate the operating principle of the (HEFSM) using segmental rotor. Moreover the profile of flux linkage, cogging torque, and torque characteristics at various armature current densities of both the (HEFSM) and (FEFSM) using segmental rotor are observed based on 2D-finite element analysis (FEA). Initially performances show that HEFSM using segmental rotor produces torque of 18 Nm with low cogging torque and sinusoidal flux waveform. Thus by further design optimization the proposed motor will effectively achieve the target performances.

New Topology of Single-Phase Segmented Rotor Field Excitation Flux Switching Machine for High Density Air-Condition

Various topologies of 3 phase and single phase Field Excitation Flux Switching Machines (FSMs) have been develop recently due to the advantages of veriable flux capability of DC Field Excitation coil located on the stator as well as robust single piece rotor structure suitable for high speed applications. However, the fundamantel principles of the develop machine with salient pole rotor, requires overlap winding between armature and FEC, creating the problems of high end coil, huge size of motor as well as high copper losses. Therefore, in this paper, a new topology of single phase segmented rotor FEFSM with 12S-6P configuration is presented with the advantage of non overlap armature and FEC windings, a smaller machine with low copper loss is designed. In this study, the principle of single phase 12S-6P with segmental is an investigated using 2D-FEA finite element analysis to validate the torque, speed and power characteristics. As conclusion, the proposed design is suitable for high density air-conditioner because 1kW power generated at 1.8Nm and the corresponding speed of 4977r/min.

Characteristics Analysis of a Novel Segmental Rotor Axial Field Switched Reluctance Motor with Single Teeth Winding

A novel 12/10 axial field switched reluctance motor (AF-SRM) is proposed for cooling fan applications in this paper. Unlike from conventional structures, the proposed motor uses the axial field instead of the radio field, the rotor is constructed from a series of discrete segments, and the stator poles are constructed from two types of stator poles: exciting and auxiliary poles. This concept improves the torque capability of a previous design by reducing the copper volume, which leads to a higher efficiency. To verify the proposed structure, the finite element method (FEM) and Matlab-Simulink are employed to get characteristics of the proposed SRM. Finally, a prototype of the proposed motor was tested for characteristic comparisons.

Design and Analysis of a Segmental Rotor Type 12/8 Switched Reluctance Motor

In this paper, a novel 12/8 segmental rotor type switched reluctance motor (SRM) is proposed for cooling fan applications. Unlike conventional structures, the rotor of the proposed structure is constructed from a series of discrete segments, and the stator is constructed from two types of stator poles: exciting and auxiliary poles. Moreover, in this structure, short flux paths are taken and no flux reversion exists in the stator. While the auxiliary poles are not wound by the windings, which only provide the flux return path. When compared with the conventional SRM, the proposed structure increases the electrical utilization of the machine and decreases the core losses, which may lead to a higher efficiency. To verify the proposed structure, the finite element method (FEM) and Matlab-Simulink are employed to get the static and dynamic characteristics of the proposed SRM. Finally, a prototype of the proposed motor was tested for characteristic comparisons.

Comparison of Wound-Field Switched-Flux Machines

This paper proposes a three-phase wound-field switched-flux (WFSF) machine. It is found that this machine has much higher average torque compared with the conventional 12-slot/8-pole machine with a segmented rotor and 12-slot/5-pole WFSF machine under the constraint of the same copper loss. All of those machines have been optimized to achieve the maximum torque for comparison. The performances of four machines, including back electromotive force, cogging torque, and static torque, are analyzed and compared by 2-D finite-element analysis and validated by experiments on the prototype machines.

A New PM-Assisted Synchronous Reluctance Motor With Three-Dimensional Trench Air Gap

This paper proposes a new 3-D motor with a trench-shaped air gap. The proposed motor has high torque without rare-earth magnets compared to conventional 2-D single air gap motors due to its multiple air gap and ferrite permanent-magnet-assisted segment rotor poles. First, the practical design is described of the winding and side stator core composition, which increase the air-gap area. Second, the reduction method of eddy-current loss in the side stator core is described. Finally, it is confirmed by finite-element analysis and some experimental data that the motor efficiency is improved without reducing torque output.

Modular switched reluctance machine with E-core stators and segmental rotors for high reliability applications

In this paper a novel modular switched reluctance machine (SRM) with E-core stators and segmental rotors is presented. Unlike the conventional SRMs, there are hybrid radial and axial magnetic paths in the E-core stators due to the particular construction. An approximate and simplified 2D finite-element analysis (FEA) model is proposed to calculate its magnetic characteristics and compared with 3D FEA model results. A comparison of the static magnetic characteristic and dynamic performance between the modular SRM and a conventional SRM is made to emphasize the superiority of this novel SRM. Furthermore, the fault tolerant performance of this modular SRM under open-circuit faults is also presented. Finally, a prototype machine is built and tested in the laboratory. The flux linkage characteristics are experimentally obtained by indirect method and are compared with FEA results. Other experimental results such as single-pulse operation, closed-loop control operation, fault-tolerant operation at open-circuits and sudden change in load torque operation are also presented to validate the analytical and simulation results of the modular SRM and its performance.

Design procedure of segmented rotor switched reluctance motor for direct drive applications

Switched reluctance motors (SRM) are becoming increasingly popular because of the rising cost of permanent magnets. It was reported that segmented rotor construction improves the torque output and efficiency. This study discusses an SRM with segmented rotor construction designed for direct drive application. Such a motor has an outer rotor. It is found that in such machines, the torque output increases when there are higher number of rotor segments than stator poles. A segmented rotor SRM with 12 stator poles and 26 rotor segments is discussed here. It has unique pole tip shape, which improves torque output. Design procedure of the motor is presented. Moreover, limitations of segmented rotor SRMs having a higher number of rotor segments than stator poles are also identified, and possible solutions are suggested. Experimental results on the prototype of a three-phase 12/26 motor are presented.

Reducing Cogging Torque in Flux Switching Motors With Segmented Rotor

A flux switching machine with a segmented rotor is an attractive alternative for driving high torque density and high-speed applications. However, a motor doubly salient structure causes torque ripples as well as acoustic noise and vibrations. In this paper, the cogging torque of the motor is analyzed and reduced by imposing notches into the segments. Different numbers and shapes of notch are considered, and their effects on the motor cogging torque, developed torque, and back electromotive force (EMF) are investigated analytically. After optimization of the motor cogging torque, the suitable notch number and shape are introduced. Finite-element analysis is employed to confirm the analytical results. In addition, the finite-element results are compared with the presented experimental results.

Optimized Segmental Rotor Switched Reluctance Machines With a Greater Number of Rotor Segments Than Stator Slots

Segmental rotor switched reluctance machines have been demonstrated to produce significantly more torque than conventional switched reluctance machines because each coil is able to link more magnetic flux. In previous work, the range of topologies studied has been relatively restricted; there has been no consideration of the range of stator tooth and rotor segment number options, and the designs have not been formally optimized in any way. This paper seeks to address this: Using finite-element toolsets for optimization, it describes the resulting machines-uniquely featuring a greater number of rotor segments than stator teeth. This paper assesses the credible tooth and segment options, with each option optimized to maximize torque capability. From this assessment, conclusions are drawn, which contrast each machine's performance based on criteria including torque production and loss. In order to validate this optimization process, a prototype machine is built, and its performance is compared with these predictions.

Axial Flux Segmented SRM With a Higher Number of Rotor Segments for Electric Vehicles

Motors for in-wheel electric vehicle application should have high specific torque. In addition, these motors should be rugged, insensitive to vibration, and temperature variation. Therefore, segmented rotor switched reluctance motor (SSRM) could be an attractive alternative to permanent magnet-based motors, which are being used for this application. A limitation of SSRM is that it requires full pitch winding for its operation. Since, in-wheel motors have high diameter to axial length (D/L) ratio, SSRM of these dimensions would be bulky and has high copper loss due to full pitch winding. Hence, in this paper, a novel SSRM with nonoverlapping winding is proposed. This motor is an axial flux SSRM (AFSSRM) with toroidal winding arrangement. It has single-stator, dual-rotor configuration with 12 stator poles and 16 rotor segments on each rotor disc. Design procedure for AFSSRM is developed and a flowchart describing the design algorithm is presented. A finite element method-based simulation is carried out to verify the performance of the proposed AFSSRM. In order to validate the performance of the motor, a prototype is fabricated and experimental results are presented.

DSP Based Simulator for Speed Control of the Synchronous Reluctance Motor Using Hysteresis Current Controller

This paper presents the field oriented vector control scheme for synchronous reluctance motor (SRM) drives, where current controller followed by hysteresis comparator is used. The test motor has a star-connected wound stator and a segmental rotor of the multiple barrier type with an external incremental encoder to sense rotor position. The magnetic characteristics of this motor are described using 2D finite element method, which is used firstly for rotor design of SRM. The field oriented vector control, that regulates the speed of the SRM, is provided by a quadrature axis current command developed by the speed controller. The simulation includes all realistic components of the system. This enables the calculation of currents and voltages in different parts of the voltage source inverter (VSI) and motor under transient and steady state conditions. Implementation has been done in MATLAB/Simulink. A study of hysteresis control scheme associated with current controllers has been made. Experimental results of the SRM control using TMS320F24X DSP board are presented. The speed of the SRM is successfully controlled in the constant torque region. Experimental results of closed loop speed control of the SRM are given to verify the proposed scheme.

Permanent-Magnet Flux-Switching Synchronous Motor Employing a Segmental Rotor

This paper introduces a three-phase segmental-rotor flux-switching synchronous motor employing permanent-magnet (PM) excitation in the stator. Flux-switching machines operate with bipolar flux and flux linkages and are therefore associated with high torque densities. Employing a segmental rotor significantly alters the scheme for flux switching from that with toothed rotors but provides a means to deploy radially acting magnets in the stator teeth. The whole arrangement presents advantages of fault tolerance capability, brushless operation, easy cooling, and simplicity of construction. A three-phase motor is developed on a 12-tooth stator with six radial magnets and a rotor with eight segments. Design considerations are applied to the location and shape of the magnets. The developed design has attraction for low-cost applications as the torque capability per unit mass of magnets deployed is found to be about 1.4 times as much as that for conventional PM synchronous motors of the same general size. Measurement results on experimental machines show that the segmented-rotor motor with PM excitation can achieve nearly twice the torque density of the similar-sized segmented-rotor motor with a dc field winding.

Investigation of the $dq$-Equivalent Model for Performance Prediction of Flux-Switching Synchronous Motors With Segmented Rotors

An equivalent <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> model of three-phase flux-switching synchronous motors employing a segmental rotor is constructed and tested for predicting steady-state performance. Both the wound-field and permanent-magnet excited motors are represented. The unconventional topologies of the two types of motors present significant departure from the basic assumptions of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> theory, even though the motors may be operated from a drive incorporating generic <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> control regimes. The equivalent <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> inductances and flux linkages are calculated from finite-element simulation results and applied in predicting the steady-state performance of the motor. It is found that the credibility of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> model to predict the performance of the motors over the operating range is assured and is enhanced by incorporating <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -coupling inductances in the model.

Speed Closed-Loop Control for Switched Reluctance Motor with Segmental Rotors Based on Angle Position Regulation

This paper describes the structure and the magnetic circuit of switched reluctance motor with segmental rotors (SSRM), and presents the control strategy of speed closed-loop by regulating the turn-on angle of the main switches in the power converter based on PI algorithm. The turn-off angle is optimized according to different speeds of the motor. The deviation of the rotor speed is the input control parameter of PI controller, and the turn-on angle is the output control parameter. The strategy of current chopping control is used for comparing with angle position control when rotor speed is high. Both the simulation and experimental results show the well transient, steady performance and robustness of SSRM based on the angle position controller.