Three-phase Switched Reluctance Motor Research Articles

Design of Two-Phase Switched Reluctance Motor (SRM) for Two-Wheel Electric Vehicle and Torque-Density Based Comparison With Three-Phase SRM

Design of Two-Phase Switched Reluctance Motor (SRM) for Two-Wheel Electric Vehicle and Torque-Density Based Comparison With Three-Phase SRM

Investigation of Effective Cases of Radial Force Sum Flattening for Acoustic Noise Reduction in Four Three-Phase Switched Reluctance Motors With Different Pole Configuration

Investigation of Effective Cases of Radial Force Sum Flattening for Acoustic Noise Reduction in Four Three-Phase Switched Reluctance Motors With Different Pole Configuration

A space vector PWM fed SRM with full bridge power converter

In order to reduce the torque ripple of a switched reluctance motor in the electric vehicles, a space vector pulse width modulation (SVPWM) driving method for the switched reluctance motor (SRM) is proposed. With a ring structure, a three-phase SRM can be driven by using a standard full-bridge power converter instead of the conventional asymmetric H-bridge. Based on this type of driving topology, an SVPWM method is applied for driving the SRM. The SVPWM method is compared to the conventional SRM driving method by using the asymmetric H-bridge, the results show that the SVPWM can reduce the torque ripple in the SRM effectively. The experimental validation is also made to verify the proposed driving topology and method, of which the results match well with the simulated results.

Analysis of Skewing Effects on Radial Force for Different Topologies of Switched Reluctance Machines: 6/4 SRM, 8/6 SRM, and 12/8 SRM

Reducing vibration and noise in electrical machines for a given application is not an easy task, especially when the application imposes some restrictions. There are many techniques for reducing vibration based on design or on control. Switched reluctance motors (SRMs) have a double-saliency structure, which results in a radial pulsation force. Consequently, they cause vibration and acoustic noise. This paper investigates the correlation between the radial force and the skew angle of the stator and/or rotor circuits. The analysis is computed from two-dimensional (2D) transient magnetic finite-element analysis (FEA) of three machine topologies, namely the 12/8 three-phase SRM, the 6/4 three-phase SRM and the 8/6 four-phase SRM. Compared to SRM, these topologies have the same basic dimensions (stator outer diameter, rotor outer diameter, and length) and operate in the same magnetic circuit saturation. The flux linkage and torque characteristics of the different motors are presented. The radial force distributed on the stator yoke under various skewing angles is studied extensively by FEA for the three machines. It is also demonstrated the effect of skewing angles in the reduction of radial force without any reduction in torque production.

Average torque distribution strategy for low speed operation of three-phase SRM with low-resolution rotor position sensor

An average torque distribution (ATD) strategy for low-speed operation of three-phase switched reluctance motor (SRM) with hall-effect rotor position sensor, as well as a calibration method for the sensor, are proposed. The sensor can only detect unaligned and aligned positions of all phases, and these positions evenly divides an electrical cycle into six position sectors. These positions are fully utilized by shaping a phase current as a four-step waveform and controlling motor average torque in each sector. In commutation sectors, a motor average torque reference is distributed into two phase average torque references. The distribution is optimized offline to minimize torque ripple and copper losses based on the phase torque characteristics. Compared with the torque control schemes using square-wave current references, the proposal can greatly reduce torque ripple without or with only a small penalty on copper losses. Based on difference among the aligned position detection errors of the hall-effect sensor, a calibration procedure for the sensor is developed. This procedure can ensure the absolute value of the average of these errors less than the maximum difference among these errors without high-resolution position signal as reference. Experimental results demonstrate effectiveness of the proposed ATD strategy and the calibration.

Dual Three-Phase Flux-Modulated Switched Reluctance Motor Drive With Maximum Torque per Ampere Strategy

This paper proposes a novel dual three-phase flux-modulated switched reluctance motor (SRM) drive with maximum torque per ampere (MTPA) capability. Different from the existing open-winding structure, the stator winding is in dual three-phase connection, which effectively eliminates the side effects of the zero-sequence harmonic voltage component. Hence, the modulating region of the space vector pulse width modulation (SVPWM) can be enhanced together with the increase of the dc-link voltage utilization ratio. The mathematical models of the dual three-phase flux-modulated SRM in the stationary reference frame and synchronous rotating reference frame are analyzed in detail. By considering the inductance nonlinearity, the MTPA control strategy is proposed based on the polynomial fitting method, which not only improves the torque capability but also simplifies the calculation of the current control system. The contributions of fundamental and harmonic currents to the electromagnetic torque are considered. By online adjusting the ratio of the dc-biased current component to the ac current component, the torque capacity can be improved. Besides, the effectiveness of the proposed MTPA control strategy can be enhanced by suppressing the harmonic current components caused by distorted back-EMF. Experimental validations are provided to verify the effectiveness of the proposed SRM drive.

Electromagnetic Torque Analysis of SRM 12/8 by Rotor/Stator Pole Angle

This paper presents the harmonic torque reduction by the different rotor pole angles of a three-phase 12/8 switched reluctance motor via an analytical model and simulation method. Improving torque performance by stator and rotor angles was applied for three-phase switched reluctance motor at stator pole/rotor pole ratios of 6/4, 8/12, 18/12, and 24/18. The average torque and the torque ripple effect by stator and rotor pole embrace have been recently studied in many projects. Due to the fact that leakage flux, flux density, and inductance are affected by the stator and rotor pole angles non-linear and linear leakage flux curves occur. Many stator and rotor pole angle combinations for the three-phase switched reluctance motor have already been done via a finite element method. In this paper, turn-on and turn-off angles will be figured based on stator and rotor pole embraces.

Multi-Physics Simulation of 6/4 Switched Reluctance Motor by Finite Element Method

The switched reluctance motor (SRM) performance can be improved by either drive control and/or machine design. However, the drive control may be more complex and expensive depending on the SRM design, whereas a favorable SRM design may result in simpler and cheaper drive control system. In order to evaluate the SRM performance before designing the control/drive system, it is important carrying out a multi-physics simulation of the machine, in such way that if electromagnetics, structural and thermal performance do not cope with the requirements for simpler control/drive system, the SRM can be redesigned until reach a feasible goal. This paper presents a comprehensive simulation analysis of a 6/4 three-phase SRM using the finite element method as evaluation approach for future use in optimization design techniques. First, the main geometrical parameters of the motor were calculated and then static and dynamic simulations were conducted to analyze the motor electromagnetic performance. Afterwards, the natural frequencies and vibration modes were found through modal analysis. Finally, the thermal analysis was accomplished to investigate the internal temperature rise due to the copper losses. The analysis has been performed in ANSYS package, providing an insightful guidance for the near optimum motor designing stage.

Integrated G2V/V2G Switched Reluctance Motor Drive With Sensing Only Switch-Bus Current

In this article, the integrated drive for three-phase switched reluctance motor (three-phase SRM) is proposed, and it combines a battery-powered bidirectional dc/dc converter to provide bidirectional power transfer in practice. In the proposed integrated drive, there is no relay to reconfigure and no need to add separate charging/discharging units and circuit components. Only one physical current sensor is used to sense the switch-bus current to provide all current signals not only for SRM driving, but also grid-to-vehicle/vehicle-to-grid functions at a standstill. The proposed integrated drive and its control are implemented and demonstrated by the provided results.

DC-Biased Sinusoidal Current Excited Switched Reluctance Motor Drives Based on Flux Modulation Principle

This article proposes a novel current control technique for three-phase switched reluctance motor (SRM) drives with harmonic current suppression, based on developed flux modulation principle. For conventional SRM control systems, the unsmooth and discontinuous stator current cause serious torque ripple, vibration, and noise, due to the doubly salient motor structure. In order to overcome shortcomings in conventional drives, the developed flux modulation principle is employed for the SRM in this article, where the working principle is investigated in detail, including the excitation magnetic field, flux modulator, and armature magnetic field. Then, a new control strategy is presented to generate the dc-biased sinusoidal current, by employing the modular open-winding converter. Furthermore, a harmonic current suppression strategy is put forward for the new drive to improve the motor performance, by employing a developed vector proportional integral control scheme. Compared to existing SRM drives, the torque ripple and motor vibration can be both significantly reduced, the motor structure and winding arrangement do not need to be changed, and the robustness of the motor system is improved. Finally, experiments are carried out on a three-phase 12/8 SRM prototype to verify the effectiveness of the proposed SRM drive and control strategy.

A Novel Driving Method for Switched Reluctance Motor With Standard Full Bridge Inverter

This article proposes a new driving method for a switched reluctance motor (SRM) by using a standard full bridge. The windings in the SRM are connected in series to build a ring structure, where a controllable DC source is inserted. Based on the new structure, the theoretical analysis and calculation are made to determine the control parameters. Besides three-phase SRM, the new idea can also be applied to the SRMs with four and five phases. The new driving method is compared with the conventional method by simulation. The results show that with the new method, the ripple of torque and speed in the SRM reduces. The influence of the proposed method on the power rating and losses is then analyzed. The validation is also made to verify the application of the new method and the difference between the conventional driving method and the proposed method. The measured results match the simulated results well.

Torque ripple reduction of switched reluctance motor by optimising switch angle based on analytical modelling

To reveal the torque ripple mechanism of switched reluctance motors (SRMs), an analytical instantaneous torque model considering current harmonics is established based on the analysis of the air-gap magnetic field. The results show that torque ripple contains third-order harmonic components in a three-phase SRM and mainly comes from the current harmonic, the rotor slotting, and their interaction. Then, the influence of main current harmonics on the torque ripple is investigated based on an analytical calculation method and it is found that the filtering of the second-order current harmonic is more conducive to reducing the torque ripple. Finally, the influence of the turn-on/turn-off angle on each harmonic current is fully analysed by means of the analytical modelling of current, based on which the second-order current harmonic and torque ripple is reduced by optimising the turn-on/turn-off angle. Also, it is found that the suitable prior turn-on angle and delayed turn-off angle is helpful to reduce the torque ripple.

A Novel Structure of Switched Reluctance Machine With Higher Mean Torque and Lower Torque Ripple

Switched reluctance motors (SRMs) have a robust and simple structure, high reliability because of the absence of magnetic field source on rotor, low cost and simple cooling system. However, conventional SRMs confront with some challenges such as low mean torque, low torque density and high torque ripples. For wider applications of SRM, the above-mentioned drawbacks must be mitigated. One possible method is changing the structure of SRMs. In this article, a novel 12/14 three-phase SRM with connected C-core structure is introduced which has a short path for the main flux of stator teeth. This brings about core loss reduction. On the other hand, both teeth of the stator phase in C-core develop a positive torque during the movement of the rotor from the unaligned position to the aligned position; this enhances the torque, the mean torque and torque density of the proposed SRM, keeping the volume fixed. Finally, the proposed SRM was prototyped and tested and its torque/rotor angular position characteristic was measured. To verify the novelty and merits of the proposed SRM, its mean and peak torque, torque density, core losses and torque ripples were compared with those of an optimized 12/8 three-phase conventional SRM and a significant match was achieved.

Online Calibration of Sensorless Position Estimation for Switched Reluctance Motors With Parametric Uncertainties

This article proposes an online calibration strategy of sensorless position estimation for switched reluctance motors (SRMs) with parametric uncertainties. For conventional sensorless SRM drives, the voltage drops on power devices and the winding resistance changing with the current and temperature are neglected, which affects the accuracy of the estimated position. In this article, an inductance calculation scheme is proposed to improve the real-time position estimation with these parametric uncertainties. First, the calculation errors of the flux linkage and inductance are both investigated and the error correction of the estimated rotor position is analyzed in detail. Then, the inductance values of the current overlapped phases are calculated. The dc component of the phase inductance is online adjusted, where all three phase inductances can be easily obtained accordingly. Finally, the real-time rotor position is acquired by the coordinate transformation of the calculated three-phase inductance during the current overlapped region. Compared to conventional SRM sensorless drives, the error of the estimated position due to parametric uncertainties can be significantly reduced without pulse injection, extra hardware, and prestored flux linkage and inductance profiles. The simulation and experiments are carried out on three-phase and four-phase SRMs to validate the effectiveness of the proposed scheme.

The use of input capture method to increase torque on switched reluctance motor

Electric drives are used in many industrial applications, one of these is Switched Reluctance Motor (SRM). Such a motor is used because it has a simple construction, efficient, and low cost. Three-phase switched reluctance motor commonly has some stators and rotors, which is implemented on the asymmetric converter. To operate the Switched Reluctance Motor, an optical encoder or hall-effect sensor will affect motor performance. To improve motor performance, the input capture method is used. Such a method can give accurate commutation angel so the excitation can be given in proper angel and increases torque on SRM. To verify the proposed method, analysis, and experimental tests were done.

Novel Switched Reluctance Machines for Domestic Appliances

Switched reluctance motors (SRM) are the core components of household appliances, which directly affect the performance and quality of household appliances. We have studied the application of switched reluctance motors in the home appliance industry. The 12/8-pole three-phase switched reluctance motor with a new rotor structure was proposed for the performance of SRM and the performance is simulated by MATLAB tools. Besides, the control principle and the operating equations of the switched reluctance motor are also introduced and deduced in detail. For the further work, although the 12/8 pole switched reluctance motor can effectively reduce the torque ripple, it cannot be completely eliminated. Therefore, the next step should continue to explore ways to reduce torque ripple.

Switched reluctance motor design for electric vehicles based on harmonics and back EMF analysis

Permanent magnet synchronous motors are widely accepted in automotive applications. The high torque density, high rotational speed with maximum efficiency in electric vehicle applications is technically challenging for motor design. However, these machines are expensive and difficult to work at high-temperature harsh environment due to permanent magnets demagnetisation features. Alternatively, switched reluctance motors can provide similar output characteristics and a wider speed. Thus these are considered to be more fault tolerant and more reliable. This study proposes a 20 kW, three-phase switched reluctance motor and analyse its overall performance and harmonic contents. The study is conducted by optimising the slot filling factor, excitation voltage and switching sequence of an asymmetrical half bridge converter. A finite element model is used to predict the core and copper losses and other influencing parameters. Simulation results are presented and analysed the effectiveness of the proposed switched reluctance motor (SRM).

Resonance Reduction by Optimal Switch Angle Selection in Switched Reluctance Motor

It is well-known that current and radial vibration harmonic may cause resonance and will thus cause severe vibration and acoustic noise in a switched reluctance motor (SRM). However, not each order of harmonic will cause resonance. It has not been fully discussed which order of current and radial vibration harmonic is the most important. This paper proposes an analytical method to derive the most important order of current and radial vibration, which lays significant foundation for resonance reduction method. Then, influence of different switch angles on current and radial vibration is analytically derived and comprehensively discussed. Based on that, resonance can be reduced by optimal switch angle selection considering efficiency sacrifice. Both simulations and experiments on a three-phase sample SRM have verified the correctness of the analytical method and effectiveness of the optimal switch angle selection method.

Rotor position tolerant detection method for SRM drive system with misaligned position sensors

Accurate rotor position is necessary for the control of switched reluctance motors (SRMs). Generally, three position sensors are ideally installed 120 electrical degrees apart for three-phase SRMs. However, the placement of position sensors may be inaccurate, particularly in small-size SRMs, and there is no method reported to deal with this problem up to now. Firstly, the position signals and the influence of the misaligned sensors on the detected rotor position are investigated. Then a novel method is developed to identify the misaligned position sensors with dynamic time warping (DTW) algorithm. The DTW distance versus the misaligned angle is calculated, and the relationship between them is described with linear regression analysis algorithm. Then the rotor position tolerant detection method is realised by compensating the misaligned angle in real time. Finally, comparative experiments are carried out on a three-phase 12/8 SRM drive system, and it can be found that the proposed strategy is capable of providing an accurate rotor position for the SRM drive system. The presented method is easy for online implementation and can be integrated into the control system conveniently.

Modular Full-Bridge Converter for Three-Phase Switched Reluctance Motors With Integrated Fault-Tolerance Capability

In this paper, a novel modular full-bridge converter is proposed for three-phase switched reluctance motors (SRMs), which provides an advanced fault-tolerance solution for both the open- and short-circuit faults in switching devices. The proposed converter is composed of two standard six-pack switch modules, providing great benefits for industrial massive production due to the modular topology. Under normal conditions, bidirectional current excitation is developed in the proposed converter, where all the switching devices are actively involved, which makes full use of the switches and averages the heat dissipation for the heat sink design. When a switch fault occurs, the fault signature can be extracted by detecting the characteristics of phase currents and operation modes, and effective fault-tolerance strategies are further applied to achieve the fault-tolerance operation accordingly. Under switch open-circuit faults, the faulty phase is adjusted to unidirectional current excitation without degrading the motor performance. Under switch short-circuit faults, the motor can still work steadily with a single six-switch inverter module by easily reconstructing the proposed converter, without losing any phase windings. The simulation and experiments on a three-phase 12/8 SRM are carried out to validate the feasibility of the proposed converter and control techniques.